Electrical Inspection & Testing Guidance Note

0.06
Guidance Note 3
Inspection & Testing
Updated to BS7671:2018+A2.2O22
IET Wiring Regulations
Guidance Note
The Institution of
Engineering and Technology
of
The Institution
Engineering and Technology
0.06
Guidance Note 3
Inspection & Testing
Updated to BS 7671:2018+A2:2022
lETWiring Regulations
Published by the Institution of Engineering and Technology, London, United Kingdom
The Institution of Engineering and Technology is registered as a Charity in England & Wales (no. 211014) and
Scotland (no. SC038698).
| The Institution of Engineering a n d Technology is the institution formed by the joining
together o f the IEE(The Institution of Electrical Engineers) and the HE (The Institution
of Incorporated Engineers).
© 1992, 1995, 1997, 2002The Institution of Electrical Engineers
© 2008, 2012, 2015, 2018, 2022The Institution o f Engineering and Technology
First published 1992 (0 85296 537 0)
Reprinted (with amendments to Section 17) 1993
Second edition (incorporating Amendment No. 1 to BS7671:1992) 1995 (0 8 5 2 9 6 867 1)
Third edition (incorporating Amendment No. 2 to BS7671:1992) 1997 (0 85296 956 2)
Fourth edition (incorporating Amendment No. 1 to BS7671:2001) 2 0 0 2 ( 0 85296 991 0)
Reprinted (with new cover) 2003
Reprinted (incorporating Amendment No. 2 to BS 7671:2001) 2 0 0 4
Reprinted (with amendments to imprint page) 2006
Fifth edition (incorporating BS 7671 :2008) 2008 (978-0-86341-857-0)
Reprinted 2009, 2010
Sixth edition (incorporating Amendment No. 1 to BS 7671:2008) 2012 (978-1-84919-275-0)
Seventh edition (incorporating Amendment Nos. 2 and 3 to BS7671:2008)
2015 (978-1-84919-873-8)
Reprinted (with minor corrections) 2015
Eighth edition (incorporating BS 7671:2018) 2018 (978-1-78561-452-1)
Ninth edition (incorporating Amendment No. 2 to BS 7671:2018) 2 0 2 2 (978-1-83953-236-8)
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Typeset in the UK by The Institution o f Engineering a n d Technology, Stevenage
Printed i n the UK by Sterling Press Ltd, Kettering
Contents
Cooperating organizations
6
Acknowledgements
7
Preface
8
Introduction
11
Chapter 1
General requirements
13
1.1
Safety
13
1.2
1.3
Required competence
The client
15
16
1.3.1
Certificates and reports
16
1.3.2
Rented domestic and residential accommodation
16
1.3.3
The Construction
17
(Design a n d Management)
Regulations 2015
1.4
Additions and alterations
17
1.5
Departures and non-compliance
18
1.6
Record-keeping
18
1.7
Installations requiring specialist knowledge, training or experience
19
Chapter 2
Initial verification
21
2.1
Purpose o f initial verification
21
2.2
Certificates
22
2.3
Required information
23
2.4
Frequency of subsequent inspections
24
2.5
Initial inspection
25
2.6
2.5.1
General procedure
25
2.5.2
Comments o n individual items to b e inspected
25
2.5.3 Inspection checklist
Tests associated with initial verification
2.6.1 Test results
46
54
54
2.6.2
Electrical Installation Certificate (EIC)
55
2.6.3
Model forms
55
2.6.4
The sequence of tests
55
2.6.5
Continuity o f protective conductors, including main
and supplementary
bonding
56
2.6.6 Continuity o f ring final circuit conductors
2.6.7 Insulation resistance
62
67
2.6.8 Confirming SELVor PELV circuits by insulation resistance testing
73
2.6.9
Testing of electrically separated circuits
74
2.6.10 Testing of functional extra-low voltage (FELV) circuits
2.6.11 Proving and testing o f non-conducting
(insulation resistance/impedance
75
location
of floors and walls)
76
2.6.12 Polarity testing
78
2.6.13 Earth electrode resistance testing
79
G u i d a n c e N o t e 3: I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
3
2.6.14 Protection by automatic disconnection
2.6.15 Earth fault loop impedance
o f supply (ADS)
(EFLI) verification
85
85
2.6.16 Prospective fault current (Ipf)
88
2.6.17 Phase sequence testing
93
2.6.18 Operation a n d functional testing o f RCDs
95
2.6.19 Other functional testing
2.6.20 Verification o f voltage drop
102
102
2.6.21 Verification o f protection of low voltage (LV)
installations against temporary overvoltages
due to faults i n the high voltage (HV) or LV system
103
2.6.22 Verification o f protection against overvoltages of atmospheric
origin or due to switching
104
2.6.23 Verification of measures against electromagnetic
disturbances
105
2.6.24 Prosumer's electrical installations (PEIs)
106
Chapter 3
Periodic inspection and testing
109
3.1
Purpose of periodic inspection and testing
109
3.2
Necessity for periodic inspection and testing
109
3.3
Electricity at Work Regulations (EAWR)
110
3.4
3.3.1
3.3.2
The need for appropriate inspection and testing
Safety in inspection and testing
3.3.3
Diverted neutral currents
111
Design
111
3.5
Routine checks
112
3.6
Required information
113
3.7
Frequency of periodic inspections
114
3.8
Requirements for periodic inspection and testing
3.8.1 Process: prior to carrying out inspection a n d testing
117
117
3.8.2
General procedure
3.8.3
Setting inspection and testing samples
3.9
Periodic inspection
3.10
Periodic testing
3.10.1 General
3.9.1
118
Example checklist of items that require inspection
123
128
128
3.10.2 Tests to be made
128
3.10.3 Additional notes on periodic testing
130
3.11
Electrical Installation Condition Report (EICR)
3.12
Periodic inspection of installations constructed
Chapter 4
133
to an earlier edition
Test instruments and equipment
135
137
4.1
Instrument standard
137
4.2
Instrument accuracy
138
4.3
Low-resistance ohmmeters
139
4.4
Insulation resistance testers
140
4.5
EFLItesters
140
4.6
Earth electrode resistance testers
143
4.7
RCD testers
143
4.8
Phase rotation instruments
144
4.9
Thermographic equipment
144
Chapter 5
5.1
5.2
G u i d a n c e Note
119
123
of BS 7671 or the IEE Wiring Regulations
4
110
111
Forms
Initial verification (inspection
Minor works
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
149
and testing) forms
149
150
5.3
Periodic inspection and testing
150
5.4
Examples of completed model forms for certification and reporting
151
Appendix A
Maximum permissible measured earth fault loop
impedance (EFLI)
171
Al
Tables
171
A2
Appendix 3 of BS 7671
176
A3
Methods of adjusting tabulated values of Zs
177
Appendix B
Resistance of copper and aluminium
conductors
181
Bl
Standard overcurrent devices
B2
Steel wire armour (SWA), steel conduit a n d steel trunking
184
B3
Mineral-insulated
184
Appendix C
Appendix D
copper-sheathed
183
cable
Use of a n earth leakage current clamp meter t o
provide an indication of the state of insulation
185
Safety check for diverted neutral currents
187
DI
Dangers associated with diverted neutral currents
187
D2
H o w to check for diverted neutral currents
187
Index
191
Guidance
© The Institution
Note 3 : Inspection & Testing
of Engineering
a n d Technology
5
Cooperating
organizations
The Institution
o f E n g i n e e r i n g a n d Technology
m a d e by the following
a c k n o w l e d g e s the invaluable
in the preparation
individuals
o f t h i s Guidance
contribution
Note:
Institution of Engineering and Technology
H. R . Lovegrove IEng FIET
R. Wickens
M. Peace CEng M E T MCIBSE
Eur Ing L. Markwell
R. Giddings
Eng
MSc BSc(Hons)
CEng M E T MCIBSE L C G I
M E T ACIBSE
G. G u n d r y M E T
We would like to thank the following organizations for their continued support:
BEAMA Ltd
BCA
Certsure, t r a d i n g as NICEIC
City & Guilds
EAL
ECA
Electrical C o n t r a c t o r s ' A s s o c i a t i o n of S c o t l a n d (SELECT)
Electrical Safety First
Health a n d Safety Executive (HSE)
IHEEM
NAPIT
Revised, compiled and edited:
Eur Ing G. Kenyon BEng (Hons)
Guidance
N o t e 3 : I n s p e c t i o n & Testing
© The Institution
o f Engineering
a n d Technology
CEng MIETTechlOSH
Acknowledgements
References to British Standards, CENELEC Harmonization
Documents and International
Electrotechnical Commission (IEC) Standards are made with the kind permission of the
British Standards Institution (BSI).
Complete copies can b e obtained by post from:
BSI Customer Services
389 Chiswick High Road
London, W4 4AL
Tel: + 4 4 0345 080 9 0 0 0
Email: [email protected]
BSI also maintains stocks of international and foreign standards, with many English
translations. Up-to-date information o n BSI Standards can b e obtained from the BSI
website: www.bsigroup.com
Illustrations of test instruments
were provided by G Kenyon Technology Ltd.
Other illustrations, from different sources, are acknowledged
Cover design a n d illustration
http://studiostuntdouble.com/.
within the text.
were created by Ken Dobson at Studio Stunt Double:
It is strongly recommended that anyone involved
in work o n or near electrical
installations possesses a copy of The Electricity at Work Regulations 1989. Guidance
o n Regulations (HSR25) published by the Health and Safety Executive (HSE).
Copies of Health and Safety Executive documents
and approved codes o f practice
(ACOP) c a n be obtained from:
HSE Books
Customer Services
PO Box 2 9
Norwich, NR3 1GN
Tel: + 4 4 (0)333 202 5070
Email: [email protected]
Web: http://books.hse.gov.uk
G u i d a n c e N o t e 3: I n s p e c t i o n & Testing
© The Institution
o f Engineering
and Technology
7
Preface
This Guidance Note is one of a number of publications prepared by the Institution
of Engineering and Technology (IET) t o explain a n d enlarge upon the requirements
in BS 7671:2018+A2:2022, Requirements
Regulations. BS 7671 is a joint publication
for Electrical
Installations,
IET Wiring
o f the British Standards Institution and the
Institution of Engineering and Technology. All references to B S 7 6 7 1 in the text o f this
Guidance Note are references t o the current 18th Edition o f the IET Wiring Regulations,
unless otherwise noted.
From herein, BS 7671 :2018+A2:2022 is referred to as BS7671. T h e year reference will
only b e included where there is a need to reference a requirement
m a d e in an earlier
edition, such as BS 7671:2008.
Note that use of this Guidance Note does alone n o t provide compliance withBS7671.
Its content is intended
to explain some of the requirements
should always consult BS 7671 to satisfy themselves
of BS 7671. Readers
of compliance and must rely
upon their o w n skill and judgement w h e n making use of the guidance provided within
this publication.
The scope generally follows that of BS7671; t h e relevant regulations and appendices
are noted in the margin. Due to the introduction
in 2 0 1 6 of CENELEC Harmonized
Document (HD) 6 0 3 6 4 - 6 covering inspection and testing, the clause numbering
in
B S 7 6 7 1 aligns with that in the HD. As a result, Chapters 61 to 6 3 are n o t used; the
text o f Part 6 of BS 7 6 7 1 starts at Chapter 6 4 . Apart f r o m the testing of insulation
resistance a n d residual current devices (RCDs), the requirements
for inspection and
testing have not significantly changed f r o m BS 7671 :201 8.
Some Guidance Notes also contain material not currently included i n BS 7671, but
which was present in earlier editions of the Wiring Regulations. All o f the Guidance
Notes contain references to other relevant sources of information.
Electrical installations in the United Kingdom
that comply w i t h BS 7671 are likely
to satisfy the relevant parts o f statutory regulations
such as the Electricity at Work
Regulations 1989 (EAWR). However, this cannot be guaranteed. It is stressed that
it is essential to establish which statutory and other regulations apply and to install
accordingly. For example, a n installation in premises subject t o licensing may have
requirements
different f r o m or additional to those of BS 7671, and these will take
precedence.
8
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
BS 7671
applies to the design, erection
including
additions
a n d verification
of electrical installations,
and alterations to existing installations and to the inspection,
testing and reporting
of existing installations. Existing installations that have been
installed in accordance with earlier editions of the Regulations may not comply with
the current edition in every respect, but this does n o t necessarily mean that they
are unsafe for continued
use or that they require upgrading. The person or persons
carrying out the inspection and testing of such an installation must decide whether
the installation is safe and suitable for continued use. Inspection and testing can only
be conducted according to the requirements o f the current version of BS 7671. The
inspector must determine whether any shortcomings are classified as safety issues or
recommendations for improvement.
Other related electrical installations, such as emergency
lighting, fire alarms and
information
and communication
technology (ICT) systems, have their own installation
requirement
standards such as BS 5266, BS 5839 and BS 6701 respectively. These
may have installation, inspection, testing and certification requirements over and above
those required i n BS 7671. It is the responsibility of the duty holder to maintain all
their installations appropriately, and the extent of the inspection and testing, and the
standards to which it is conducted, should b e agreed before any work is undertaken.
The inspector is reminded that for a periodic inspection and test of a n existing
installation, their duty is to assess the suitability of the existing installation for continued
use, subject to any agreed limitations
and exclusions. They must therefore
make
sufficient inspection and tests to enable them to make that assessment. In addition, it
is the duty of the building or site dutyholder to maintain their installation so that it is
safe and to undertake such maintenance as is necessary to achieve this.
Users of this Guidance Note should assure themselves that they have complied
with
any relevant legislation, including, where applicable, legislation that post-dates the
publication.
G u i d a n c e N o t e 3: I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
9
NOTES
10
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Introduction
This Guidance Note is concerned primarily with Part 6 of BS 7671 (Inspection
testing) along with Appendix 6 (Model forms for certification and reporting).
and
Neither BS 7671 nor the Guidance Notes are design guides. It is essential to prepare
a full design and specification prior to commencement
or alteration of an electrical
installation.
514.9
The design and specification should set out the requirements
and provide sufficient
information to enable competent persons to carryout the installation and to commission
it. The specification must include a description of how the system is to operate and
all the design and operational parameters. It must provide for all the commissioning
procedures that will b e required a n d for the provision of adequate information
user. This will be by means of a n operational and maintenance
to the
(O&M) manual or
schedule, and 'as-built' drawings, if necessary.
It must be noted that it is a matter of contract as to which person or organization is
responsible for, i n turn, the design, specification, construction
and verification of the
installation a n d any operational information.
The persons or organizations who m a y b e concerned i n the preparation of the works
include:
(a) the designer (see the Construction
(CDM) for information
(Design and Management)
Regulations 2015
o n designers' duties);
(b) the installer (contractor or if there is m o r e than one, principal contractor and
contractors);
(c) the verifier;
(d) specialist commissioning
engineers;
(e) the distributor of electricity (the distribution
network operator (DNO));
(f) the installation owner and/or user (and, where applicable for CDM, the client.
Where there is a domestic client, the client's duties are undertaken by the
contractor or, if there is more than o n e contractor, the principal contractor);
(g) the architect (and, where CDM applies, the principal designer);
(h) the fire risk assessor;
(i)
specialist manufacturers
or suppliers;
( j ) area Building Control bodies;
( k ) any regulatory authority:
(l) any licensing authority;
(m) any specialist insurers; and
(n) the Health a n d Safety Executive (HSE).
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
11
The revision o f the CDM Regulations has given guidance on the duties required of a
designer. Aswell ascarrying out the actual design layout and calculations and specifying
the materials and installation requirements:
"Designers are those, who as part of a business, prepare or modify designs for a
building, product or system relating to construction work.
When preparing or modifying designs, to eliminate, reduce or control foreseeable risks
that m a y arise during:
1
2
construction;
and
the maintenance and use of a building once it is built.
Provide information to other members of the project team to help them fulfil their duties."
Details of each i t e m of equipment
sect
51
should b e obtained f r o m the manufacturer and/or
supplier and compliance with appropriate standardsconfirmed.
Health and safety o f all installation a n d inspection a n d testing staff and any other
persons i n the premises is vital and a work plan including
risk assessments a n d
method statements must b e agreed with all parties and put in place before any work
is undertaken.
The installation operational manual must include a description
as installed is to operate, maintenance
of how the system
provisions and all test and commissioning
records. The manual should also include manufacturers’
technical data for all items
of switchgear, luminaires, accessories, etc. and any special instructions that may b e
needed. The Health and Safety at Work etc. Act 1974 Section 6 and the Construction
(Design and Management) Regulations 2015 are concerned with the provision
of information,
and guidance
o n the preparation of technical manuals is given i n
BS EN IEC/IEEE 82079-1 Preparation
of information
of products
- Principles and general
requirements
information
o n construction
and services. The size and complexity of the
products
for use (instructions
and BS 4940
for use)
series Technical
installation will dictate the nature and extent of the manual.
With regard to the inspection a n d testing of an existing installation, it is necessary to
agree a detailed specification of the requirements of the client, including any limitations.
12
G u i d a n c e Note
3: I n s p e c t i o n & Testing
© The Institution of Engineering a n d Technology
1
General
requirements
1.1
Safety
Before any work can begin, a work programme should b e agreed with the client and a
health a n d safety plan, including risk assessments and method statements, agreed and
put in place. It m a y be that work has to be carried out when the premises is operating
and staff are present, and they must not b e exposed to any safety risks. Work areas
should b e fenced off w i t h temporary
be left unattended
barriers a n d electrical equipment
should not
when open. There should be adequate workspace, access and
lighting appropriate to t h e work being carried out, and during electrical testing it is often
necessary to provide temporary task lighting as parts, or all, of the installation m a y
be isolated. Escape routes must be kept open at all times or temporary
alternatives
arranged. Where supplies have to b e isolated, it is necessary that this is planned i n
advance with the premises management. Health and safety guidance (HSG) Electricity
a t work: Safe working practices (HSC85) recommends
managers establish a system
of rules and procedures wherever electrical work is to b e carried out, or ensure that
contractors brought in to d o electrical work have appropriate rules and procedures.
Initial verification, and some maintenance
activities, o f fixed electrical installations fall
within the scope of the Construction (Design and Management) Regulations 2015 (CDM).
For private domestic clients, the contractor, or, if there is m o r e than one, the principal
contractor, undertakes the client's duties.
Electrical inspection
a n d testing inherently
involves some degree of hazard. It is
therefore the inspector's d u t y to provide for their o w n safety, and that of others, in
the performance of the test procedures. The testing safety procedures detailed in the
Health and Safety Executive Guidance Note Electrical test equipment
for use on low
voltage electrical systems (CS38) should be observed. Where testing does not require
the equipment
or part of an installation to be live, it should be made dead and safely
isolated. Guidance on live and dead working can b e found i n the HSE publication The
Electricity at Work Regulations 1989. Guidance on Regulations (HSR25). Guidance
o n safe isolation procedures can be found i n Best Practice Guide No.2. Guidance o n
the management
of electrical safety and safe isolation procedures for low voltage
installations, published by Electrical Safety First.
G u i d a n c e Note 3 : Inspection
© T h e Institution
o f Engineering
& Testing
and Technology
13
When using test instruments,
(a) understanding
safety can b e achieved by precautions such as:
the equipment
to b e used, its rating and the characteristics of
the installation upon which it is proposed to use the equipment.
(b) checking
that
the instruments to
be
used conform to the
appropriate
British Standard safety specifications. These are BS EN 61010 series Safety
requirements for electrical equipment for measurement, control, and laboratory
use and BS 5458:1977 (IEC 141:1973) Specification for safety requirements for
indicating and recording electrical measuring
instruments
BS 5 4 5 8 has n o w been
is the standard
instruments
withdrawn,
but
and their accessories.
to
which
older
should have been manufactured.
(c) checking any test equipment before use to see that it is complete and not damaged.
(d) checking that test leads, including any probes or clips used, are i n good order,
are clean and have no cracked or broken insulation. Where appropriate, the
guidance given i n GS38 should b e observed for test leads. This recommends
the use of adequately insulated test equipment, probes, connectors, a n d test
leads, suitable for the insulation overvoltage category in which tests are being
conducted (see Table 1.1). Suitable high breaking capacity (HBC) fuses o r other
means of limiting current, should be provided i n test leads o r test equipment.
Such measures help reduce the risks associated w i t h both accidental contact,
a n d arcing under fault conditions.
▼ Table 1.1 Explanation of installation overvoltage category (CAT) markings on test
equipment, leads, probes and other connecting equipment
Installation overvoltage
category marking
Note:
Description of where test equipment with this
marking can be used in an electrical installation
(see HSE Guidance Note GS38, and Annex K to
BSEN 61010-1:2010+A1:2019)
CATII
Equipment intended to b e supplied from the building
wiring. This overvoltage category applies to both
plug-connected equipment and permanently
connected equipment.
CATIII
As CATII, plus equipment intended to form part of the
building wiring installation. Such equipment includes
socket-outlets, distribution boards.
CATIV
As CATIII, plus equipment installed at or near the origin
o f the electricity supply to a building, between the
building entrance and the primary distribution board
(consumer unit). Such equipment may include electricity
meters and primary overcurrent protective devices.
The equivalent overvoltage category for a test arrangement is the lowest overvoltage
category of any equipment, including test instruments, leads, probes, connectors, and
similar, connected in the test arrangement.
Particular attention
should b e paid to the safety aspects associated w i t h any tests
performed with instruments capable o f generating a test voltage greater t h a n 5 0 V AC
o r 120 V DC in dry conditions, or 2 5 V AC or 6 0 V DC i n wet or damp conditions, or
which use the supply voltage for the purposes of testing earth electrode, earth fault
loop impedance and operation of residual current device(s) (RCD). Note the warnings
given in Section 2.6.16 through to Section 2.6.19 of this Guidance Note.
14
G u i d a n c e N o t e 3 : I n s p e c t i o n & Testing
© The Institution of Engineering a n d Technology
Electric shock hazards can arise from, for example, capacitive loads, such as when
cables become charged in the process of an insulation resistance test, or voltages o n
t h e earthed metalwork whilst conducting a loop test or RCDtest. The test limits quoted
in these guidelines are intended to minimize the chances of receiving anelectric shock
during tests.
Under some conditions, such as when working at height, particular care needs to be
taken even with touch voltages below 5 0 V A C or 120 V DC. A spark, or contact with
touch current at the limit of perception,
m a y cause an inspector or test equipment
operator to be startled and jump or physically jolt away f r o m the contact, resulting in
a fall or other serious incident. It is important to address such hazards when carrying
out risk assessments before work begins.
1.2
Required competence
641.6
Skilled persons carrying out the inspection
651.5
must as, appropriate to their function, have a sound knowledge and experience relevant
to the nature of the installation being inspected and tested, and of B S 7 6 7 1 and other
and testing of any electrical installation
relevant technical standards. (Such persons are generally referred t o in this Guidance
Note as 'the inspector';
this may b e o n e or more persons, depending
o n the work
being undertaken.)
Inspectors must also have the relevant education a n d experience to enable them to
perceive risks and avoid the dangers that electricity can create, and be fully versed
in the inspection and testing procedures. This can best be shown by the inspector
holding a recognized inspection and testing qualification, along with a current level 3
certificate in the requirements
for electrical installations BS 7671.
Furthermore, the inspector must employ suitable test equipment during t h e inspection
and testing process, be familiar with its operation, and have sufficient
experience in interpreting the results with regard to the requirements
inspection
of BS 7671.
It is worth noting that the person responsible for inspection and testing may b e required to
formally demonstrate competence by means of registration/certif ication under a recognized
scheme or membership
of a recognized trade body, or, for example, as a condition of
contract and/or as a requirement of the Local Authority Building Control (LABC).
It is the responsibility of the inspector, for either the initial or periodic inspection and
testing, as appropriate, to:
641.4 (a) prevent danger to any person or livestock and prevent property damage;
641.3 (b) compare the inspection and testing results with the design criteria (where
available), with BS 7 6 7 1 and/or with previous records, as appropriate;
(c) confirm compliance with the current edition of BS 7671, or any non-compliance
(non-conformity with BS 7671) that may give rise to danger;
(d) take a view on related issues that might constitute or give rise to danger of
the installation itself, or its interface with the premises, such as the condition
connected
electrical equipment,
the condition
of distributor's
condition
of building fabric to which electrical equipment
equipment,
of
or the
is secured, or through
which wiring systems pass (for example, fire stopping); and
(e) take a view and report o n the condition of the installation.
G u i d a n c e Note
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15
In the event of a dangerous situation being found, the inspector should recommend
the immediate isolation of the defective item of equipment.
work should b e informed, in writing, of this recommendation
1.3
The person ordering t h e
without delay.
The client
1.3.1 Certificates and reports
644.1
653.1
Following the initial verification of a new installation, or changes to an existing installation,
an Electrical Installation Certificate (EIC), together with a Schedule(s) of Inspections
and a Schedule(s)of Test Results, is required to b e given to the person ordering the
installation work.
Likewise, following
the periodic inspection a n d testing of an existing installation,
a n Electrical Installation Condition
Report (EICR), together
w i t h Condition
Report
Inspection Schedule, Schedule(s)of Circuit Details and Schedule(s) of Test Results, is
required to b e given to the person ordering the inspection.
Sometimes the person ordering the work is not the user of the installation. I n such
cases, it is necessary for the user (for example, the employer or householder)
t o have
a copy of the certificate (together with the records o f inspections and test results).
It is recommended that those providing documentation to the person ordering the
work also recommend
that a copy of the forms b e passed to the user, including any
purchaser o f a domestic property. For rented accommodation,
this m a y b e required
by legislation (see Section 1.3.2).
Copies of any certificates o r reports along with their associated schedules should b e
kept in the operational a n d maintenance (O&M) documentation
1.3.2
for t h e premises.
Rented domestic and residential accommodation
In England and Wales, Sub-Section (l)(b)
of Section 11 of the Landlord and Tenant
Act 1985 (Repairing obligations in short leases) implies that a landlord "shall keep in
repair and proper working order the installations in the dwelling-house for the supply
of water, gas and electricity".
Asimilar requirement can b e found in Section 13 of Chapter 4 of the Housing (Scotland)
Act 2014, which states that the electrical installation must b e in a reasonable state
of repair, in order to comply with the Act. The legislation goes on to state that the
installation must b e maintained.
The above Acts d o not directly specify periodic inspection a n d testing of a n electrical
installation. Periodic inspection a n d testing is a means of demonstrating compliance
with the Acts. The Scottish Government
has published
guidance o n meeting
the
tolerable standard a n d repairing standard in Scotland, which can b e downloaded
from: https://www.gov.scot/publications/electrical-installations-and-appliances-privaterented-properties/.
The Electrical Safety Standards i n the Private Rented Sector (England) Regulations
2 0 2 0 apply t o all n e w tenancies i n private rented properties
in England f r o m 1 July
2020, a n d all existing tenancies f r o m 1 April 2021. This legislation requires an EICRto
b e prepared at an interval o f n o t m o r e than 5 years (or shorter period if the inspector
considers it necessary). The legislation also requires specific persons, such as tenants,
new tenants before they occupy the premises, or, o n written request, local authority
16
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© The Institution of Engineering and Technology
housing authority, to receive copies o f the EICR (or EIC if an EICR has not b e e n
conducted within 5 years of an EIC for the entire installation being issued). Inspection
and testing of rented properties
is also required in Scotland. Whilst over a n d above
t h e requirements in legislation, landlords should b e aware that damage may occur to
parts o f the electrical installation, and, where practicable, can consider an electrical
inspection o n change of tenancy.
Any repairs m u s t b e carried out by an electrically skilled person or an electrically
competent person under their supervision. The landlord is responsible for confirming
the competency
of any contractors carrying out such work. Advice for landlords on
the legislation, including
guidance
o n n o w to find a competent person t conduct
the test, can b e found o n the UK Government website a t the following address:
https://www.gov.uk/government/publications/electrical-safety-standards-in-theprivate-rented-sector-guidance-for-landlords-tenants-and-local-authorities/guide-forlandlords-electrical-safety-standards-in-the-private-rented-sector.
1.3.3
The Construction (Design and Management) Regulations 2015
The client a n d contractors have duties for health, safety a n d welfare according to t h e
CDM Regulations. F o r a private domestic client, the contractor (or, if more than o n e
contractor, the principal contractor) assumes the client's duties.
1.4
644.1
641.3
Additions and alterations
Every addition or alteration to an existing installation must comply with the current
edition of B S 7671 and must not impair the safety of the existing installation. The
relevant inspection and testing requirements of Chapter 64 also apply to additions and
alterations and, in particular, to the replacement o f a distribution board or consumer
unit. In order to verify that an addition o r alteration to an electrical installation complies
with BS 7671, the relevant parts of the existing installation must b e inspected
and
tested to confirm the safety of the addition or alteration, including, for example, the:
(a) circuit ratings;
(b) circuit conductor sizes;
(c) means of earthing;
(d) protective conductor continuity; and
(e) earth fault loop impedance (EFLI).
644.1 .2 While there is no obligation to inspect and test any part of the existing installation that
does not affect and is not affected by the addition o r alteration, any defects with the
existing installation that are observed during the course of the works, that may give
rise to danger, b u t d o n o t affect the safety of the addition or alteration, are required to
be noted in the ’Comments on existing installation’ section of an EIC (single-signature
or multiple-signature)
or o n Minor Electrical Installation Works Certificates (MElWCs).
If there is insufficient space to complete this information,
a separate document
could
b e used and referred to in the certificate.
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
17
1
1.5
Departures and non-compliance
These terms are now frequently
used in certificates and reports a n d are defined in
Part 2 of BS 7671.
"Departure. Deliberate decision not to comply fully w i t h the requirement of BS 7671,
for which the designer must declare that the resultant degree o f safety is not less than
that achievable by full compliance."
"Non-compliance. A non-conformity
that may give rise to danger."
Note:
A non-conformity is a failure to meet a requirement of a standard.
1.6
Record-keeping
132.13 It is a requirement that the appropriate documentation called for in Regulation 514.9,
514.9 Part 6 and (where applicable) Part 7 o f BS 7671 is provided for every electrical installation.
Chapter 6 5 Records of all checks, inspections and tests, including test results, should be kept
Appx6 - throughout the working life of an electrical installation. This will enable deterioration to
guidanceto recipents b e identified, a n d could also be used as a management tool to ensure that maintenance
checks are being carried o u t and to assess their effectiveness.
For non-domestic
Management)
installations,
Regulation
12 o f the Construction
(Design
and
Regulations 2015 (CDM) requires a record known as 'the health and
safety file' to b e prepared, reviewed, updated and revised from t i m e to time to take
account of the work and any changes that have occurred. This file should contain any
information relating to the project that is likely to b e needed during any subsequent
construction work to provide for the health and safety of persons. The CDM Regulations
require that the health a n d safety file is passed o n t o the client o n completion
construction work to assist with ongoing management
of the
of the building.
The CDM Regulations also require that once the construction work has been completed,
the health and safety file remains available for inspection by any person who might need
it to comply with any relevant legal requirements. It also requires that the file is revised
and updated as often as may b e appropriate to incorporate any relevant new information.
EICs, MElWCs and EICRs (as appropriate) would constitute
relevant information
in
relation to this requirement.
For domestic installations, NHBC (National House-Building
Council) guidance
recommends that all instructions for services are passed to t h e building owner.
In both domestic and non-domestic
cases, there may also be insurance requirements
that imply or specify records.
The Electromagnetic
Compatibility
the client keep the information
electromagnetic compatibility
18
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© The Institution of Engineering a n d Technology
Regulations 2016 are statutory a n d require that
provided by the installer relating to compliance w i t h
(EMC) criteria for the life of the installation.
1.7
Installations requiring specialist knowledge,
training or experience
This Guidance Note mainly covers the general requirements
of BS7671. The following
publications provide further guidance o n types of installation, or special location, that
require additional information, experience, and/or training, for initial verification
periodic inspection, testing and certification:
710 (a) Medical
710.64
locations: refer to t h e IET Guide to Electrical Installations
and
in Medical
Locations, IET Guidance Note 7 Special Locations along with relevant English,
Scottish and Welsh Health Technical Memoranda;
( b ) Solar photovoltaic (PV) installations: refer to the IET Code
Grid-Connected Solar Photovoltaic Installations;
722 (c) Electric vehicle
charging equipment
installations:
of Practice
for
IET Code
of
refer to the
Practice for Electric Vehicle Charging Equipment Installation;
(d) Electrical energy storage systems: refer to the IET Code of Practice for Electrical
Energy Storage Systems;
(e) Fuel filling
stations:
Modification,
refer to the
Maintenance
AREA Guidance
and Decommissioning
for Design,
Construction,
of Filling Stations (also known
as the Blue Book), and the IET/APEA publication
Electric Vehicle Charging
Installations at Filling Stations;
(f) Other locations with explosive atmospheres: see BS EN 60079;
(g) Temporary power systems within the scope of BS 7909: refer to the IET
Temporary Power Systems: A guide to the application
for temporary
events and the IET Practitioner's
of BS 7671 and BS 7909
Guide to Temporary
Power
Systems;
(h) Fire protection
and fire stopping:
Against Fire;
(i) Emergency lighting
systems:
refer to IET Guidance
refer to the
Note
Electrician's Guide
4 Protection
to Emergency
Lighting Systems along with BS 5266-1; and
(j) Fire detection
Fire
Detection
and fire
alarm systems:
and
Alarm
Fire
refer to the Electrician's Guide
Systems along
with
BS 5839-1:2017
to
and
BS 5839-6:20 19+AI:2020.
This list is n o t exhaustive. The above publications
are not a substitute
for suitable
experience and/or training in those types o f installation.
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
19
NOTES
20
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© The Institution
of Engineering
and Technology
Initial verification
2.1
2
Purpose of initial verification
Verification is defined in BS 7671 as: "All measures by means of which compliance
of the electrical installation with the relevant requirements
of BS 7671 are checked,
comprising inspection, testing and certification."
642.2
Initial verification is carried out on a new installation before it is put into service. The
purpose is to confirm by way of inspection and testing, during construction and on
completion, that the installation complies with the design and construction
BS 7671, in so far as is reasonably practicable.
Appx 6, Intro (v)
aspects of
It is important to recognize the responsibilities o f the signatories for the design,
construction and verification. While the inspector is responsible for verifying aspects of
b o t h design a n d construction, they cannot, and are not m e a n t to, absolve responsibility
for their work elements from the designer and installer nor fix any problems they may find.
Example
Consider o n e aspect of the design: the inspector should check that the cable sizes, as
specified, have been correctly selected and installed. In order to do this, the design
criteria is required to be obtained, for example, a cable o r circuit schedule, and will
then carryout a visual inspection of the installed cable sizes for comparison. The m o s t
logical position to d o so will be at the distribution board housing the cables' protective
devices. It would b e unreasonable for the inspector to carry out design cable sizing
checks, as this is the responsibility of the designer.
At this point, it would also be unreasonable for the inspector to check that each cable
size at the distribution point is maintained throughout
responsibility of the installer or constructor).
the cable's length (this is the
This example illustrates the principle a n d the responsibilities
of the designer and
constructor of the installation. The inspector carries out checks, but only to confirm
the work of others.
42.3
The inspector must have adequate information o n the design details to check and
inspect against. BS 7671 provides a format list in Regulation 642.3 of items to be
checked, although this list is not exhaustive. These items are as follows:
(a) installed
electrical
equipment
applicable British or Harmonized
is of the correct
t y p e and complies w i t h an
Standard, or a foreign national standard based
o n an International Electrotechnical Commission
(IEC) Standard;
Guidance
© The Institution
Note 3 : I n s p e c t i o n & T e s t i n g
of Engineering
a n d Technology
21
2
(b) the fixed installation
is correctly selected
and erected,
taking into
account
manufacturers’ instructions;
(c) the fixed installation is n o t visibly damaged or otherwise defective
so as to
impair safety; and
(d) the installation is ready a n d safe to be used.
Sect 642
Inspections
Inspections are an important
element of inspection a n d testing and are described in
Section 2.5 o f this Guidance Note.
Sect 643 Tests
The tests are described in Section 2.6 of this Guidance Note.
644.1
Results
The results of inspection and tests are to be recorded as appropriate. The HSE's
publication HSR25 recommends that records of all maintenance, including test results,
b e kept throughout the working life o f an installation (see guidance on the Electricity
at Work Regulations 1989 (EAWR), Regulation 4(2)). This can enable the condition of
equipment and the effectiveness of maintenance t o be monitored.
643.1 R e l e v a n t c r i t e r i a
The relevant criteria are, for the most part, the requirements
of the Regulations for
the particular inspection or test. Most criteria are given i n Sections 2 and 3 of this
Guidance Note.
There will b e some instances where the designer has specified requirements
are particular to the installation concerned.
that
For example, the intended impedances
may be different from those in BS7671. I n this case, the inspector should either ask
for the design criteria or forward the test results to the designer for verification with
the intended
design. In the absence of such data, t h e inspector should apply the
requirements set o u t in BS 7671 .
Verification
The responsibility for comparing inspection a n d test results w i t h relevant criteria, as
required by Regulation 641.3, lies with the party responsible for inspecting and testing
t h e installation. This party, which may be the person carrying out the inspection a n d
testing, should sign the ’Inspection and testing’ section of the Electrical Installation
Certificate
(EIC) or the ’Declaration’ section of t h e Minor Electrical Installation Works
Certificate (MEIWC). If the person carrying o u t the inspection and testing is also
responsible for the ’Design’ and 'Construction' of the installation, the design and
construction sections of the EIC should be completed
2.2
by the same person.
Certificates
Appx 6 Appendix 6 of B S 7671 contains model forms for the initial certification of a new
installation or for a n addition or alteration to a n existing installation, as follows:
(a) the multiple-signature
(b) the MEIWC.
22
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© The Institution of Engineering and Technology
EIC; o r
2
Examples
of typical
f o r m s a r e given
Multiple-signature
Electrical
The
multiple-signature
in Section
5 of this Guidance
Installation
certificate
allows
C e r t i f i c a t e (EIC)
different
persons
c o n s t r u c t i o n , inspection
a n d testing, a n d a l l o w s two signatories
i s mutual
W h e r e designers
responsibility.
o f a n installation,
the use o f separate
a r e responsible
f o r m s would
sign
for
design,
for identifiably
be appropriate.
there
separate
parts
W h e r e the design,
a n d t e s t i n g are the responsibility
of one p e r s o n a Certificate
with
d e c l a r a t i o n a s shown
(v)
a single-signature
in
item
6 in B S 7 6 7 1 may be used in p l a c e of the multiple
of
the
form.
Minor
Electrical I n s t a l l a t i o n Works C e r t i f i c a t e (MEIWC)
T h i s c e r t i f i c a t e i s to be used
only
include
circuit,
the
provision
t o a n existing
of a new
circuit.
f o r individual
such
For several items
items
similar
but
not f o r the replacement
of minor
to
section
o f the
w o r k s that
d o not
as a n a d d i t i o n a l socket-outlet
or lighting
of minor
b e used.
T h e c e r t i f i c a t e may a l s o be used f o r the replacement
or luminaires,
Introduction
signatures
model
point
works,
a n E I C should
o f equipment
of distribution
such a s a c c e s s o r i e s
boards,
consumer
units o r
items.
2.3
Required information
BS7671
requires
o r p e r s o n s carrying
311.1
to
for design where
c o n s t r u c t i o n , inspection
Appendix
641.2
Note.
that t h e f o l l o w i n g i n f o r m a t i o n shall be m a d e available to the p e r s o n
o u t the inspection
and testing:
Assessment o f general
characteristics
( a ) the
expressed
maximum
demand,
in amps,
kW or kVA (after
d i v e r s i t y i s taken
i n t o account);
312.1
( b ) t h e number
a n d t y p e of live conductors
circuits used in the i n s t a l l a t i o n ;
of the
312.2
(c) the type of s y s t e m e a r t h i n g used
by the distributor
f o r the user;
i n s t a l l a t i o n a n d a n y facilities p r o v i d e d
by the
source(s)
( d ) t h e nominal voltage(s)
a n d i t s characteristics,
including
(e) the nature o f the c u r r e n t a n d supply frequency;
(f)
the p r o s p e c t i v e short-circuit
the installation;
origin
Note:
harmonic
and of the
distortion;
c u r r e n t at the origin of the installation;
(g) the e a r t h f a u l t l o o p impedance
( h ) the type
of energy
(EFLI) (Z e ) o f that p a r t of the system
e x t e r n a l to
and
a n d r a t i n g o f the overcurrent
protective
device(s)
(OCPDs) a c t i n g at the
of the installation.
The statutory Electricity Supply, Quality a n d Continuity Regulations (ESQCR) require
that these characteristics should be available f r o m the distribution network operator
(DNO) for all sources of supply from the public supply network.
G u i d a n c e N o t e 3 : I n s p e c t i o n & Testing
© The Institution
of Engineering a n d Technology
23
Diagrams, charts or tables
514.9.1
T h e Health a n d S a f e t y at Work etc. Act (HSWA) 1974 generally r e q u i r e s relevant
i n f o r m a t i o n to b e available a s a n a i d to s a f e use, inspection, testing a n d maintenance.
T h i s m a y i n c l u d e t h o s e i t e m s l i s t e d i n R e g u l a t i o n 514.9.1, a s f o l l o w s :
(a) the t y p e and c o m p o s i t i o n of e a c h circuit, including
a n d size of c o n d u c t o r s a n d t y p e of wiring.
points
of utilization,
This s h o u l d include
number
the
reference
m e t h o d s h o w n i n S e c t i o n 7 o f A p p e n d i x 4 of B S 7 6 7 1 ( M e t h o d s o f i n s t a l l a t i o n ) ;
(b) the method
used for compliance with the requirements
for basic and fault protection
and, where appropriate, the conditions required for automatic disconnection;
(c)
t h e information necessary f o r t h e identification of each device p e r f o r m i n g t h e
f u n c t i o n s of protection,
i s o l a t i o n a n d switching,
a n d its location; a n d
(d) any circuit or equipment vulnerable to the electrical tests specified in Part 6 of B S 7671.
2.4
Frequency
of subsequent
Note:
T h e term 'periodic inspection' implies the inclusion of any necessary tests.
The time intervals between
the recommended
inspections
dates of periodic inspections need consideration.
The p e r i o d t o t h e f i r s t p e r i o d i c i n s p e c t i o n a n d t e s t is r e q u i r e d t o b e c o n s i d e r e d a n d
r e c o m m e n d e d by t h e i n s t a l l a t i o n d e s i g n e r a n d o t h e r r e l e v a n t p a r t i e s , a s n o t e d i n
Regulations 301.1, a n d 341.1, as p a r t of the design.
T h e p e r i o d to e a c h subsequent periodic inspection s h o u l d t h e n b e considered a n d
r e c o m m e n d e d as p a r t of c a r r y i n g o u t a p e r i o d i c i n s p e c t i o n a n d test,
undertaking
that p a r t i c u l a r inspection
by the p e r s o n
a n d test.
It h a s n e v e r b e e n c l a r i f i e d w h e t h e r t h e p r o p o s e d p e r i o d t o a s u b s e q u e n t p e r i o d i c
inspection
s h o u l d b e m e a s u r e d f r o m the t i m e of t h e previous
i n s p e c t i o n o r f r o m the
t i m e w h e n a n y i d e n t i f i e d r e p a i r s have b e e n c o m p l e t e d (they
m a y never
be!).
The
i n s p e c t o r m u s t t a k e a v i e w o n t h i s ; it w o u l d p e r h a p s b e b e s t t o s e t it f r o m t h e t i m e
of the p r e v i o u s inspection,
e s p e c i a l l y if there
a r e significant
r e p a i r s identified
o r if t h e
i n s t a l l a t i o n i s p o o r l y maintained.
An inspector
must a l s o use t h e i r e x p e r i e n c e a n d skill to i d e n t i f y a s u i t a b l e p e r i o d f o r a
s u b s e q u e n t periodic
guidance
i n s p e c t i o n a n d they m u s t b e c l e a r about their reasoning.
Industry
i s available, but c a n o n l y b e general, a n d e a c h i n s t a l l a t i o n is d i f f e r e n t a n d
h a s d i f f e r e n t f a c t o r s a f f e c t i n g it. Too f r e q u e n t a n i n s p e c t i o n w i l l c a u s e u n n e c e s s a r y
costs,
but
t o o infrequent,
a l l o w significant
possible
especially
if the
dangers to develop,
installation
is p o o r l y maintained,
e s p e c i a l l y a s a n installation
may
gets older.
Regulation 652.1 gives s o m e guidance, b u t t h e inspector m u s t m a k e a reasonable
a n d i n f o r m e d decision,
a n d r e c o r d the r e a s o n s f o r t h a t d e c i s i o n o n the E I C o r E I C R , a s
they m a y need to j u s t i f y it. S o m e installations,
such a s those
subject
to l o c a l a u t h o r i t y
licensing, a r e r e q u i r e d t o b e i n s p e c t e d a t set p e r i o d s .
Section 3.7 contains further
24
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© The Institution of Engineering and Technology
guidance on the frequency
of periodic
inspection
and testing.
2
2.5
Initial
inspection
2.5.1
General
procedure
Inspection and, where required, testing should b e carried out and it is recommended
that a record of the results should b e retained throughout the different stages of erection
to enable the issue of relevant certification on completion of the verification process.
It should b e noted that Regulation 641.1 requires inspection and testing to b e carried out
during the erection stage of the installation. This is to allow the review and inspection
of work that may later b e covered and inaccessible; however, t h e inspector will require
necessary design information from the designer before any such inspections during
construction or installation.
A model Schedule of Inspections is shown in Section 5 of this Guidance Note.
2.5.2
Comments
on individual
items to be inspected
642.3 BS7671 provides a list of items considered as a minimum to be inspected, but t h e list
is not exhaustive. The inspector, where necessary, will inspect and compare the items
against data provided by the designer and installer and identify any non-compliances
or departures. However, it is not for the inspector to decide what installation items are
required o r necessary, or to identify any repairs or modifications.
Sect526 a
The list is as follows:
Connection of conductors
Every connection between
conductors and equipment/other
conductors
should
provide durable electrical continuity and adequate mechanical strength.
It is impractical for an inspector t o physically inspect all connections but they should
inspect a representative sample of connection types, especially larger connections,
such as o n switchgear and busbars. When checking connections, t h e correct torque
setting for screw or bolted terminals should b e used. (It is noted that in some cases,
such as high current busbar connections,
specialist resistance tests may b e required
that are outside the scope of BS7671.)
There are four stranding classes of conductor described in B S E N 6 0 2 2 8 :
(a) Class 1, solid, conductors.
These consist of only a single strand of conductor
forming the entire csa.
(b) Class 2, stranded, conductors.
These consist of at least 6 strands, although
some applications in Part 7 of BS 7 6 7 1 specify a m i n i m u m of 7 strands are
used for stranding class 2 conductors.
(c) Class 5, finely stranded (flexible) conductors, These are m o r e finely stranded
than Class 2 stranded conductors, and are typically found in appliance cables,
or flexible installation cables.
(d) Class 6, extra-finely stranded (extra-flexible) conductors, being m o r e finely
stranded again.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineering and Technology
25
2
Some terminals are only suitable for certain conductor stranding classes, as described
in Table 2.1.
▼ Table 2.1
Suitability of terminals for certain conductor classes
Terminal or connection
accessory marking
Remarks on suitability of terminal for certain
conductors
no marking
Suitable for any stranding class of conductor. Where
stranding class 2, 5 or 6 conductors are subject to frequent
disconnection and reconnection at screw or cage type
terminals, it is recommended that they are protected against
spreading or damage using crimp ferrules.
Similarly, stranding class 2, 5 or 6 conductors should ideally
have an appropriate crimp, such as a ring crimp, when
connecting at a stud type terminal.
Preparation of stranded conductors by soldering should only
be used under the conditions described in
Regulation 526.9.
Rigid conductors only.
r
The terminal is only suitable for stranding class 1 and 2
conductors.
Some screwless terminals marked 'r' are not suitable for
conductors prepared with crimp ferrules, and manufacturer’s
instructions should be followed.
The terminal is only suitable for stranding class 1
conductors.
sol
Some screwless terminals marked 'sol' are not suitable for
conductors prepared with crimp ferrules, and manufacturer's
instructions should be followed.
f
b
The terminal is only suitable for stranding class 5 and 6
conductors. It is not possible to terminate stranding class 1 or
2 conductors in terminals marked f.
Identification of cables and conductors
It should b e checked that each core or bare conductor is identified as necessary. The
single colour green must not b e used for the identification
of live conductors in power
circuits, protective conductors, or functional earthing and bonding conductors.
The bi-colour
combination
green-and-yellow
is only to b e used for protective
conductors. Other than protective earth and neutral (PEN) conductors, conductors that
are identified with green-and-yellow throughout their length, either as a single-core
cable, or as a core in a multicore cable, must not b e overmarked with another colour
or with alphanumeric symbols at terminations, except for the purposes of identifying
which circuit t h e cpc serves.
Again, it is impractical for a n inspector to physically inspect all identifications,
but they
should inspect a representative sample of types, especially o n larger conductors, such
as to switchgear.
26
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
▼ Table 2 . 2
Identification of conductors
Function
Alphanumeric
Colour
Protective conductor
PE
Green-and-yellow
(GNYE)
Protective bonding conductors
PB
Green-and-yellow
(GNYE)
Functional earthing conductor
FE
Pink (PK)
Line of single-phase circuit
L
Brown (BN)
Neutral of single- or three-phase circuit
N
Blue (BU)
Line 1 of three-phase AC circuit
LI
Brown (BN)
Line 2 of three-phase AC circuit
L2
Black (BK)
Line 3 of three-phase AC circuit
L3
Grey (GY)
Positive of two-wire circuit
L+
Red (RD)
Negative of two-wire circuit
L-
White (WH)
Positive (of negative earthed) circuit
L+
Red (RD)
Negative (of negative earthed) circuit
M
Blue (BU)
Positive (of positive earthed) circuit
M
Blue {BU)
Negative (of positive earthed) circuit
L-
White (WH)
Outer positive of two-wire circuit derived
f r o m three-wire system
L+
Red (RD)
Outer negative of two-wire circuit derived
from three-wire system
L-
White (WH)
Positive of three-wire circuit
L+
Red (RD)
Mid-wire of three-wire circuit
M
Blue (BU)
Negative of three-wire circuit
L-
White (WH)
L
Black (BK), Brown (BN),
Red (RD), Orange (OG),
Yellow (YE), Green (GN),
Violet (VT), Grey (GY),
White (WH), Pink (PK) or
Turquoise (TQ)
NorM
Blue (BU)
AC power circuit
Two-wire unearthed DC power circuit
Two-wire earthed DC power circuit
Three-wire DC power circuit
Control circuits, ELVand
other applications
Line conductor
Neutral or mid- wire®
Notes:
(1)
Power circuits include lighting circuits.
(2)
M identifies either t h e mid-wire of a three-wire D C circuit, o r t h e earthed conductor of a
t w o - w i r e earthed D C circuit.
(3)
Only t h e m i d d l e wire of three-wire circuits m a y b e earthed.
(4)
A n earthed PELV conductor is blue.
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
27
2
c
522.8
Routing of cables
Cables a n d their cable management
account
systems should be designed a n d installed taking
into
the mechanical stresses that users of the installation will make upon the installation.
522.6.201
A key r e q u i r e m e n t t o note i s for c a b l e s i n s t a l l e d i n a w a l l o r p a r t i t i o n a t a d e p t h o f l e s s
522 6 . 2 0 3
t h a n 5 0 mm
f r o m the
m e t a l l i c covering;
s u r f a c e . If t h e c a b l e u s e d does
not i n c o r p o r a t e a n e a r t h e d
o r is not i n s t a l l e d i n a n e a r t h e d conduit,
t r u n k i n g o r d u c t ; o r i s not
p r o v i d e d w i t h m e c h a n i c a l p r o t e c t i o n s u f f i c i e n t t o p r e v e n t d a m a g e b e i n g c a u s e d by
nails, screws
protective
or similar;
o r i s not
e x t r a - l o w voltage
supplied
via separated
extra-low
(PELV), it w i l l b e n e c e s s a r y to provide
voltage
additional
(SELV) o r
protection
by m e a n s o f a r e s i d u a l c u r r e n t d e v i c e (RCD) h a v i n g a r a t e d r e s i d u a l o p e r a t i n g c u r r e n t
not e x c e e d i n g 3 0 m A . This is a requirement
prescribed
522.6.20
even
c a b l e z o n e s d e s c r i b e d i n Regulation
where
c a b l e s a r e r u n within
A n o t h e r r e q u i r e m e n t relates to c a b l e s i n s t a l l e d in a wall or partition,
of which
contains
metallic
component
the
522.6.202.
the construction
p a r t s such a s studs, f r a m e s o r skins. I r r e s p e c t i v e
o f t h e d e p t h a t w h i c h t h e c a b l e s h a v e b e e n installed, t h e y a r e r e q u i r e d t o b e p r o v i d e d
with
additional
exceeding
protection
by a n R C D having
a rated
3 0 m A ; o r b e m e c h a n i c a l l y protected
residual
sufficient
o p e r a t i n g current
t o avoid damage
not
t o them
d u r i n g construction of t h e wall o r partition a n d d u r i n g t h e installation of t h e cables; o r
comply
with the requirements
referred
to in the previous
paragraph.
C a b l e s s h o u l d b e r o u t e d i n p r e s c r i b e d z o n e s i n w a l l s (as s h o w n below),
in Regulation
penetration
522.6.202
(especially
in dwellings),
by n a i l s a n d screws, etc. It should
as identified
to assist i n a v o i d i n g damage
b e n o t e d that t h e requirements
by
can also
a p p l y t o t h e o t h e r s i d e of t h e w a l l .
▼ Figure 2.1
S
3
3
T h e zones prescribed in Regulation 522.6.202 of B S 7671
WHMM
o
3
3
150 m m
Room 2
Room 1
Furthermore,
w h e r e c a b l e s a r e i n s t a l l e d a t a depth
of 5 0 mm
o r l e s s f r o m the s u r f a c e
of t h e w a l l o r p a r t i t i o n , t h e r e q u i r e m e n t s m e n t i o n e d i n t h e p r e v i o u s p a r a g r a p h also apply.
It will be far t o o late at the end of the construction
so it is vital that the inspector
28
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
to view and assess a n y of these things,
continually i n s p e c t s the installation w o r k d u r i n g construction.
2
Cables routed in buildings must b e fixed such that they cannot c o m e away from
their supports during fires and collapse to block escape routes or entangle firefighters
searching the building in smoke-filled conditions.
Such entanglements
have led to
fatalities in t h e past, which could have been avoided with s o m e forethought.
escape routes in a building are defined and signed: in open-plan
Not all
office areas, there
can b e several possible routes away f r o m a desk or meeting r o o m across an o p e n
office area to an escape stair (see BS 9999) and all such routes should b e kept clear
f r o m possible entanglement. An escape route is defined i n the Regulations as a "path
to follow for access t o a safe area in the event of an emergency". T h e requirement for
surface-run wiring systems n o t t o b e subject to premature collapse in the event of a
fire applies to all areas, and not just designated escape routes.
It is not difficult to look at a proposed
installation and consider the possibilities
of
cables coming away from their fixings: have only plastic ties been used, is cable tray
metal or plastic, is t h e tray upside d o w n and so on? If t h e cable supports are metal and
t h e cables are laid in or cleated t o t h e m with metal fixings, then the cable cannot go
anywhere. Even if a cable is fixed with plastic ties or clips and could drop, it may only
require an occasional metal or fire-resistant fixing to restrain it.
I n larger industrial or commercial installations, cable ladder or tray and other services
may b e suspended
together
f r o m concrete structural elements
'drop rods' screwed into the concrete. The inspector
by steel wires or
cannot physically assess the
suitability or the loading of such fixings, but may look at the design data provided to
see that what is installed is as the design.
Where cables run around or d o w n walls - for example, t o a socket-outlet - and
are contained in small-section plastic trunking, the cables should b e fixed inside the
trunking if it would b e possible for t h e trunking to deform in heat and the lid come off,
thus releasing the cables.
Appendix 13
The inspector m u s t also assess any fire protection repairs and fire-stopping where
cables have been installed through a fire-rated building structural element or wall. The
electrical installation designer should provide information in relation to fire safety with
regard to cable routes. Regulation 527.2.1 requires that openings remaining after t h e
passage of wiring systems are sealed according to the degree of fire-resistance
prescribed for the respective element of the building construction before penetration.
The seal is required to:
(a) resist the products
of combustion
to t h e same extent
as the elements
building construction which have been penetrated;
(b) provide the same degree of protection f r o m water penetration
of
as that required
for the building construction element in which it has been installed;
(c) b e compatible with the material of the wiring system that it is in contact with;
(d) permit thermal movement of t h e wiring system without reducing t h e sealing
quality; and
(e) have adequate mechanical stability to withstand
t h e stresses which may arise
through damage to the support of the wiring system due to fire.
527.2.3
Appendix 13
Where wiring system containment
(conduit, trunking, and busbar trunking systems)
passes through a building element that has specific fire resisting properties and has an
internal cross-sectional area greater than 710 m m 2 for example, a round hole of around
3 0 m m diameter, it must b e internally sealed in accordance with Regulation 527.2.3.
Guidance Note 3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
29
422
Appendix
13
T h e concept of a protected escape route h a s been introduced i n B S 7 6 7 1 :20 1 8+A2:2022 .
A protected
escape route
is defined
i n B S 7 6 7 1 a s follows:
Protected
e s c a p e r o u t e . A r o u t e e n c l o s e d w i t h specified fire-resisting
construction
designated
f o r e s c a p e to a place
of safety i n the event
of a n
emergency.
Appendix
13 Guidance
on escape
For safe escape,
protected
routes
a n d f i r e p r o t e c t i o n is provided
i n Appendix
13 to B S 7671.
as w e l l as b e i n g enclosure i n fire a n d smoke-resisting construction,
e s c a p e routes
need
to b e ' f i r e sterile', i.e. not contain
c o m b u s t i b l e material
t h a t c o u l d cause a hazard to escaping occupants. Wiring systems w i t h i n a protected
e s c a p e route s h o u l d b e l i m i t e d to t h a t f o r :
(a) l i g h t i n g ;
(b) emergency
lighting;
(c) f i r e detection
a n d alarm; a n d
(d) o t h e r e s s e n t i a l s a f e t y s y s t e m s f o r high
Cables installed
i n f i r e resisting
hazard premises.
e n c l o s u r e s a r e deemed
to b e outside
protected
escape
r o u t e s . Electrical accessories, i n c l u d i n g s o c k e t - o u t l e t s , a r e p e r m i t t e d i n p r o t e c t e d
e s c a p e routes,
provided
they d o not c o m p r o m i s e t h e s t r u c t u r e ' s f i r e resistance. S e e
S e c t i o n 527 of B S 7671.
422.2.1
Gables i n protected
escape routes shall b e as s h o r t a s practicable. C a b l e s encroaching
o n e s c a p e routes shall not be i n s t a l l e d within a r m ' s reach unless they a r e provided with
a d e q u a t e p r o t e c t i o n against m e c h a n i c a l d a m a g e t h a t m i g h t o c c u r d u r i n g e v a c u a t i o n .
C a b l e c o n t a i n m e n t o r s u p p o r t systems
in protected
e s c a p e routes
must b e classified
as n o n - f l a m e p r o p a g a t i n g , a c c o r d i n g t o t h e r e l e v a n t p r o d u c t s t a n d a r d :
(a) B S 6 1 3 8 6 f o r conduit
systems;
(b) B S E N 5 0 0 8 5 f o r t r u n k i n g s y s t e m s ;
(c) B S E N 6 1 5 3 7 f o r c a b l e t r a y o r c a b l e l a d d e r systems;
and
(d) B S E N 6 1 5 3 4 f o r p o w e r t r a c k systems.
132.7
d
S e l e c t i o n of c o n d u c t o r s
Sect 523 T h e s p e c i f i c a t i o n of c a b l e s u s e d - B S t y p e a n d designation,
t e m p e r a t u r e ratings,
selection for environmental conditions, c o n d u c t o r category a n d material, certification
to a n d c o m p l i a n c e with
the r e q u i r e d C o n s t r u c t i o n P r o d u c t s Regulations,
b e c h e c k e d , b a s e d o n the d a t a s u p p l i e d by t h e designer
etc. - must
a n d installer.
422.2.1 Cables in protected
e s c a p e r o u t e s must have a minimum
60 °/o light transmittance
when tested in accordance with B S E N 61034-2, a n d b e selected f r o m o n e of the following:
(a) c a b l e s m e e t i n g the
requirements
of Regulation
560.8.1
f o r wiring
systems
of
s a f e t y s e r v i c e s r e q u i r e d to o p e r a t e i n f i r e c o n d i t i o n s ;
(b) c a b l e s w i t h r e s i s t a n c e t o f l a m e p r o p a g a t i o n a c c o r d i n g t o t h e r e l e v a n t p a r t s o f
B S E N 60332-3
series; o r
(c) cables i n p e r m i t t e d cable m a n a g e m e n t systems m e e t i n g BS EN 60332-1-2.
B S 8 5 1 9 requires cables for both primary a n d secondary supplies to safety services to
be f i r e - r e s i s t a n t a n d t o f o l l o w d i v e r s e r o u t e s t h r o u g h t h e building.
30
G u i d a n c e Note
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© The Institution of Engineering and Technology
2
The cross-sectional area (csa) of conductors should be assessed against the overcurrent
protective arrangement and the requirements for limitation of voltage drop, based
Sect 525 upon information provided by the installation designer (where available), such as a
cable schedule or schematic diagram.
Sect 523
Sect 524
Reference should be made, as appropriate, to Appendix 4 of BS7671.
Verification of polarity: single-pole device in a TN or TT system
132.14.1
e
530.3.2
must be checked that single-pole devices for protection or switching are installed in
line conductors only, and that Edison screw (ES) lampholders are correctly connected.
f
Accessories and equipment
Correct connection (suitability, polarity, environmental factors, etc.) must be checked.
553.1.3
Table 55.1 of BS 7671 sets out the three different types of plug and socket-outlet
recognized, their ratings and their associated British Standards.
553.2.2
Particular attention should be made to the correct connection of cable couplers so that
pins of connectors (which would be accessible when the couplers are disconnected)
are connected to the load or downstream side of the connection. Couplers for cables
in which current may flow in either directions, such as some circuits in prosumer’s
electrical installations (PEIs), appropriate couplers having live parts protected to at least
IP2X on both parts of the coupler when disconnected should be used.
559.5.1.204
Bayonet lampholders B15 and B22 should comply with BS EN 61184 and have a
temperature rating T2, as described in that standard. With the exception of E14 and
E27 lampholders complying with BS EN 60238, ES lampholders used in TN and
TT systems should have the line of the supply connected to their centre contact, and
neutral connected to the outer contact. Lighting circuits incorporating B15, B22, E14,
E27 or E40 lampholders are only to b e used in a lighting circuit rated up to 16 A.
559.5.1.205
Sect 527
g
Selection and erection to minimize the spread of fire
Fire barriers, suitable seals and/or protection againstthermal effects should be provided,
if necessary, to meet the requirements of BS7671. These are good examples of items
which can and should be inspected during the erection stage.
Each sealing arrangement built around services penetrations through a fire-rated
building element should be labelled by the specialist installer to state its fire rating and
inspected to verify that it conforms to the manufacturer's erection instructions and
required rating. It is essential, therefore, that inspection should be carried out at the
appropriate stage of the work, and that this is recorded at the time for incorporation in
the inspection and test documents.
A wiring system such as conduit, trunking or ducting that penetrates a building element
that has a specified fire rating is to be sealed both internally and externally to the
degree of fire resistance of the external element. Fire barrier requirements are detailed
in Regulations 527.2.2 and 527.2.3.
Products classified as 'non-flame propagating' in accordance with BS EN 61386-1 or
BS EN 50085 are liable to catch fire as a result of an applied flame, but in which the
flame does not propagate, and which extinguish themselves within a limited time after
the flame is removed. The test to classify products as 'non-flame propagating' is a
self-extinguishing test, not a fire resistance test. The product cannot be assumed to
Guidance N o t e 3 : Inspection & Testing
©The Institution of Engineering and Technology
31
2
protect t h e cable inside it f r o m the effects of afire. The cable should h a v e its own fire/
s m o k e classification. B o t h metallic a n d non-metallic products c a n b e classed a s ' n o n
f l a m e propagating1. For f u r t h e r details see IET Guidance Note 4 Protection Against Fire.
chapter41 h
Measures o f protection against electric shock
Tables 2.3 to 2.5 list the various measures of protection
against electric shock given in
B S 7671. T h e measures are discussed in m o r e detail later in this section.
The tables divide up t h e measures into t h o s e that are generally permitted,
those that
are for use o n l y where access is restricted to skilled o r instructed persons, a n d t h o s e
t h a t are f o r u s e only where the installation is controlled o r supervised by skilled or
instructed
persons. The tables also list the provisions f o r basic protection
a n d fault
p r o t e c t i o n t h a t m a k e up t h e protective measures.
Additional protection m a y also b e specified a s p a r t o f a protective m e a s u r e under
certain conditions
o f external influence a n d in certain o f t h e special installations o r
locations. See later in this section.
▼ Table 2.3
Protective measures generally permitted
Protective measure
411
Automatic disconnection of
supply (ADS)
Protective provisions
Basic protection by
Fault protection by
Basic insulation of live parts
and/or barriers or enclosures
Protective earthing, protective
equipotential bonding and
automatic disconnection in
case of a fault
or Class II equipment
412
413
Sect 414
Supplementary insulation
Double or reinforced
insulation
Basic insulation
Electrical separation for the
supply of one item of
current-using equipment
Basic insulation of live parts
and/or barriers or enclosures
Extra-low voltage provided by
SELVor PELV
Limitation of voltage, protective separation and basic
insulation
V Table 2 . 4
or reinforced insulation
Protective measures for use only where access is controlled or supervised
by skilled persons
Protective provisions
Protective measure
Basic protection by
32
Simple separation from other
circuits and from Earth
Fault protection by
417.1
Obstacles
Obstacles
None
417.2
Placing out of reach
Placing out of reach
None
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
2
▼
Table 2 . 5
Protective measures for use only where the installation is controlled or
under the supervision of skilled or instructed persons
Protective provisions
Protective m e a s u r e
Basic p r o t e c t i o n by
Fault p r o t e c t i o n b y
418.1
Non-conducting location
Basic insulation of live parts
and/or barriers or enclosures
No protective conductor,
insulating floor and walls,
spacing/obstacles between
exposed-conductive-parts and
extraneous-co nducti ve-parts
418.2
Earth-free local equipotential
bonding
Basic insulation of live parts
and/or barriers or enclosures
Protective bonding, notices,
etc.
Electrical separation for the
supply of more than one item
of current-using equipment
Basic insulation of live parts
and/or barriers or enclosures
Simple separation from other
circuits and Earth, to non
earthed protective bonding,
etc.
N o t e s : (1) Not recognized for general application.
(2) To be used only in special circumstances.
416
(i)
Protective provision of basic protection by insulation of live
parts and/or barriers or enclosures
This p r o t e c t i v e p r o v i s i o n forms
p a r t of a n u m b e r of d i f f e r e n t p r o t e c t i v e m e a s u r e s , a s
s h o w n i n t h e previous tables.
T h e inspection
4]g
damaged
of this protective
d u r i n g installation
provision
i s to check
that insulation
a n d t h a t b a r r i e r s a n d enclosures
h a s not
been
have b e e n selected
and
i n s t a l l e d to p r o v i d e a t l e a s t a d e g r e e of p r o t e c t i o n o f I P X X B o r 1P2X a n d , f o r a h o r i z o n t a l
top s u r f a c e t h a t is r e a d i l y accessible, o f a t l e a s t IPXXD o r IP4X, a n d a r e n o t d a m a g e d
( i n s u l a t i o n r e s i s t a n c e is o f c o u r s e a f u n d a m e n t a l test
2 . 6 of this G u i d a n c e Note).
(ii)
Protective measures generally permitted
Automatic
411.2
to b e carried o u t -
Section
disconnection
see
of supply (ADS)
T h e provision
f o r b a s i c protection
in t h i s protective
m e a s u r e is b a s i c insulation of l i v e
parts and/or barriers or enclosures, the inspection of which i s discussed earlier in this section.
T h e p r o v i s i o n f o r f a u l t p r o t e c t i o n is p r o t e c t i v e e a r t h i n g , p r o t e c t i v e b o n d i n g a n d
automatic
each
d i s c o n n e c t i o n of s u p p l y i n c a s e of a fault. Although
circuit provides
evidence
b e met, it i s a l s o important
that d i s c o n n e c t i o n times
to inspect
v e r i f i c a t i o n of EFLI f o r
a c c o r d i n g to Chapter
o r o t h e r w i s e verify t h e following
41 c a n
items.
Presence of appropriate protective conductors:
(a) e a r t h i n g conductor.
(b) circuit
protective
conductors
(cpcs).
(c) p r o t e c t i v e b o n d i n g c o n d u c t o r s .
(d) m a i n b o n d i n g c o n d u c t o r s . R e g u l a t i o n 411.3.1.2 m e t a l l i c p i p e s w i t h i n t h e b u i l d i n g
c o n n e c t e d to non-conductive service p i p e s entering t h e building n e e d n o t b e
connected
to the protective
(e) s u p p l e m e n t a r y bonding
equipotential
conductors
(where
bonding.
required).
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineeringand Technology
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The type of system earthing arrangement m u s t b e stated by t h e designer, for example:
(a)
TN-C-S;
(b)
TN-S; or
(c)
TT (earth electrode(s) used as the means of earthing for t h e installation).
The earthing arrangement should b e confirmed by the DNO, and not assumed by
visual inspection.
411.5 (TN)
For installations that receive a low voltage (LV) supply f r o m the public distribution
411.5 (TT) network, the designer should also ascertain whether protective multiple earthing
(PME) conditions apply, as this affects the application of certain requirements of
BS 7671, such as t h e sizing of main protective bonding conductors, and earthing for
some of the special locations in Part 7 (for example, use of a PME earthing arrangement
is precluded for some special locations, such as caravan parks and marinas). Guidance
is available from the local DNO and in Energy Networks Association publication G12/4
Requirements
for the Application
of Protective Multiple
Earthing
to Low Voltage
Networks. PME conditions will normally apply in public LV supplies:
(a) with a TN-C-S earthing arrangement; and
(b) with a PNB earthing arrangement, where the neutral of supply is earthed
at
some distance downstream of the LV transformer, rather than at the transformer
itself. PNB is used by DNOs where it is necessary t o separate HV and LV
earthing systems.
The EFLImust b e appropriate for the protective device, i.e. RCD or overcurrent device,
and within the values given in the relevant tables in Chapter 41 of BS 7671.
Double or reinforced insulation
412.1
For double insulation, basic protection is provided
protection is provided by supplementary insulation.
For reinforced insulation, both basic protection
by basic insulation,
a n d fault protection
and fault
are provided by
a single application of reinforced insulation between live parts and accessible parts.
Where double or reinforced insulation is to b e employed a s t h e sole protective measure,
it is important to confirm that t h e installation or circuit so protected will remain under
effective supervision so as to prevent any unauthorized
change(s) being m a d e that
could impair the effectiveness of t h e measure.
Electrical separation for the supply of one item of current-using equipment
413.1.1 Electrical separation is a protective measure where basic protection is provided by
basic insulation of live parts and/or by barriers and enclosures, in accordance with
Section 416, and fault protection is provided by simple separation o f t h e separated
circuit f r o m other circuits and f r o m Earth.
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Extra-low voltage (ELV) provided b y S E L V o r P E L V
Sect 414 ForSELVand PELV, requirements include:
414.1.1
(a) the nominal voltage must not exceed 5 0 V AC or 120 V DC or the lower limits
specified for a special location
Regulation 414.1.2);
414.1.2
414.3 (b)
414.1.1
(c )
d
a
suitable source, for example, a safety isolating transformer to BS EN 61558-2-6
or BS EN 61558-2-8;
protective separation f r o m all non-SELVor PELV circuits;
414.1. ;; ( ) f°
414.4.4
according to Part 7 of BS 7 6 7 1 (see note to
r
SELV, basic insulation between the SELV system and Earth; and
e
( ) SELV exposed-conductive-parts must have n o connection
with Earth, exposed-
conductive-parts or protective conductors of other systems.
(iii)
Protective measures for use only where access is controlled
or supervised by skilled persons
Obstacles
41
Protection by obstacles provides basic protection only, n o t fault protection. It protects
against unintentional
contact with live parts.
Where this measure is used, the area must b e accessible only to skilled persons or to
instructed persons under their supervision.
The measure is not to b e used in some installations and locations of increased shock
risk. See Part 7 of BS7671.
Placing out of reach
417
Placing out of reach also provides basic protection only. The distances referred to in
Regulations 417.3.1 and 417.3.2 should b e increased where long or bulky conducting
objects are likely to b e handled in t h e vicinity, taking account of the dimensions
of
those objects.
410.3.5
Bare live parts are only permitted in areas where access is controlled or supervised
by skilled persons. The dimensions of passageways should be checked against the
information given in Appendix 3 of t h e HSE's guidance o n HSR25 (see Section 729).
Sect 729
Section 7 2 9 (Operating and maintenance gangways) covers situations where open
switchgear or busbars are permitted and where access is restricted to skilled or
instructed persons. Inspection for verification in areas covered by Section 7 2 9 requires
careful checking, including the measurement of separation distances, for example,
those associated with 'arm's reach', as per Figure 417 of BS 7671; these must b e
confirmed with the installation isolated. However, it must be noted that the EAWRtake
precedence in all cases and their requirements
for accessible live conductors must b e
followed in all cases.
G u i d a n c e N o t e 3: Inspection
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(iv)
Protective measures for use only where the installation is
controlled or under the supervision of skilled or
instructed persons
Non-conducting
location
Where this protective measure is employed, such as in a n electronic equipment test
area, it must be verified (amongst other things) that all installed electrical equipment
m e e t s the requirements of Section 416 with regard to provisions for basic protection.
418J.2
Further, t h e exposed-conductive-parts of t h e installation should b e so arranged that
it is not possible for persons to make simultaneous contact with either two exposedconductive-parts,
or an exposed-conductive-part and any extraneous-conductive-part
under normal operating conditions, if these parts are liable to b e at different potentials
as a result of failure of the basic insulation of a live part.
The inspector should confirm the achievement of this and check that within t h e
location there are n o protective conductors (see also the specific test for this m e t h o d
in Section 2.6.12 of this Guidance Note).
418.2
Earth-free local equipotential
bonding
The use of this protective measure is intended to prevent the appearance of a
dangerous touch voltage under fault conditions. In some cases, this protective measure
is combined with the protective measure of electrical separation.
Where protection by earth-free local equipotential bonding is employed, it must b e
verified (amongst other things) that all installed electrical equipment should meet t h e
requirements
of Section 416 with regard to provisions for basic protection.
’ All simultaneously accessible exposed-conductive-parts and extraneous-conductiveparts should b e interconnected by local protective bonding conductors.
418.2.3
Measures m u s t b e taken to ensure that the local protective bonding conductors are not
connected to Earth either directly or unintentionally via the exposed- and extraneousconductive-parts
to which they are connected.
A warning notice complying with Regulation 514.13.2 m u s t b e fixed in a prominent
position adjacent to every point of access to the location concerned.
The inspection, supplemented
with tests, should verify that n o item is earthed within
the area and that n o earthed services or conductors enter or traverse the area, including
t h e floor and ceiling. Inspection should confirm whether or n o t this has b e e n achieved.
Electrical separation for the supply to more than o n e item of current-using equipment
418.3
Sect 413
it is intended
to supply more than one item of current-using equipment using
electrical separation, it will b e necessary to m e e t the requirements of Regulation 418.3.
This is in addition to meeting the requirements of Section 413, some of which are
referred to earlier in this section of this Guidance Note in relation to the use of electrical
separation for the supply of one item of current-using equipment.
418.3.3
The separated circuit should b e protected f r o m damage and insulation failure.
Any exposed-conductive-parts of t h e separated circuit should b e connected together by
insulated, non-earthed protective bonding conductors, which should n o t b e connected
to the protective conductor or exposed-conductive-parts
extraneous-conductive-parts.
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© The Institution of Engineering and Technology
of any other circuit or to any
2
418.
Socket-outlets should have a protective conductor contact, which is connected to the
protective bonding system described above.
All flexible cables should contain a protective conductor for use as a protective bonding
conductor, except where such a cable supplies only items of equipment
having double
or reinforced insulation.
If two faults affecting two exposed-conductive-parts occur, and where conductors
of different polarity feed these, a protective device should disconnect the supply in
accordance with t h e disconnection
418/
time given in Table 41 .1 .
The product of t h e nominal voltage (volts) a n d length (metres) of the wiring system
should not exceed 100,000 Vm and the length of the wiring system (metres) should
n o t exceed 5 0 0 m.
(v)
Additional protection
Additional protection by one o r more RCDs
415.1.1 It should b e confirmed that an RCD selected to provide additional protection has a
rated residual operating current
not exceeding 3 0 m A and complies with the
relevant standards.
Generally, all socket-outlets
up to and including 3 2 A rating should b e provided with
additional protection by a 3 0 m A RCD; however BS 7671 allows this to b e omitted for
some socket-outlets in certain locations such as non-domestic installations where a
written risk assessment shows that such additional protection is not required. It is not
for the inspector to consider or approve the risk assessment, but the inspector should
see the assessment to prove that it exists, so that the requirement
of the regulation
is fulfilled. The assessment should also b e attached to the Electrical Installation or
MEIWC, for future reference.
415J.2 It should also b e confirmed that appropriate protective measures in accordance with
Sections 411 to 414 are in place, as an RCD m u s t not b e used as the sole means of
protection against electric shock.
Additional protection by supplementary
protective equipotential
bonding
415.2.1 Where supplementary bonding is provided, it should encompass all simultaneously
accessible exposed-conductive-parts of fixed equipment, extraneous-conductive-parts
and the protective conductors of all equipment in the location where this protective
measure is being applied.
415.2.2 The effectiveness of supplementary equipotential bonding, as provided, may b e verified
where the resistance between simultaneously accessible exposed-conductive-parts and
extraneous-conductive-parts fulfils whichever of the following conditions is applicable:
(a)
for AC systems, R < 5 0 V/I a ; and
Note:
In medical locations of Group 1 and Group 2, and in fuel filling stations installed in
accordance with APEAGuidance for Design, Construction, Modification, Maintenance
and Decommissioning of Filling Stations, the voltage is reduced from 50 V to 25 V.
G u i d a n c e N o t e 3 : I n s p e c t i o n & Testing
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(b)
for DC systems, R < 120 V/I a
where la is the operating current of the protective device in amps (for overcurrent
devices, this is the 5 s operating current, and for RCDs, | n).
5313
RCDs should be selected in accordance with Regulation 531.3. Selection of RCDs
should take into account the residual fault current operating characteristics of loads
with respect to DC components.
Type AC RCDs shall only be used for fixed equipment, where it is known that the
load current contains no DC components. This precludes the use of socket-outlets
incorporating Type AC RCD protection (SRCDs)to BS 7288.
Note:
Type AC RCDs are not p e r m i t t e d i n medical locations.
The RCD residual current operating characteristic Type can be identified by the marking
provided by the manufacturer. See Figure 2.34.
▼ T a b l e 2 . 6 Types o f RCD currently recognized by B S 7 6 7 1
Description of RCD
Abbreviation
used in
BS 7671
Residual current
operating characteristic
type
(If not from BS 7671)
Standard
Type AC (Note 1)
Residual current
circuit-breaker without
overcurrent protection
B S E N 61008
Type A
RCCB
Type F
BS EN 62423
Type B
Type AC (Note 1)
Residual current
circuit-breaker with
overcurrent protection
B S E N 61009
Type A
RCBO
Type F
B S E N 62423
Type B
Socket-outlet
incorporating RCD
protection
Fused connection unit
incorporating RCD
protection
Circuit-breaker
incorporating residual
current protection
SRCD
Type A (Note 2)
BS7288
Type AC (Notes 1,2)
FCU RCD
Type A (Note 2)
BS7288
Type AC (Notes 1,3)
CBR
Type A (Note 3)
BS EN 60947-2
Type B (Note 3)
Type AC (Notes 1,3)
Modular RCD
MRCD
Type A (Note 3)
BS EN 60947-2
Type B (Note 3)
Notes:
1
2
3
4
38
O n l y t o b e used for fixed equipment, w h e r e it is k n o w n that t h e load current contains
n o DC components.
Additional protection only. Cannot b e used to m e e t disconnection times required by
Chapter 41 o f BS 7 6 7 1 for automatic disconnection of supply.
For operation b y skilled or instructed persons only.
RCCBs, RCBOs, CBRs a n d MRCDs are also available w i t h a time-delay option. These are
k n o w n as S-Type a n d identified with t h e relevant marking, see Figure 2.34.
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
2
Sect 515
'
Prevention of m u t u a l detrimental influence
Regulations 132.11 and 515.1 require electrical equipment
to b e so selected and
erected that there will b e no harmful influence (such as electromagnetic
interference
(EMI) or heat) between t h e electrical installation and other electrical and non-electrical
installations. The inspector is advised to give careful thought to this while carrying o u t
t h e inspection.
132.5.1 This, however, does not include the detrimental influence of other systems onto
t h e electrical installation, such as water leaks or splashing, which are covered by the
requirements of Regulation 132.5.1.
Sect 537
j
Isolating and switching devices
BS EN 60947-1
Low voltage switchgear
and controlgear.
General
rules
defines
standard utilization categories that allow for conditions of service use and t h e switching
duty to b e expected.
All switch utilization categories must b e appropriate for the nature of the load (see
Table 2.7). It would b e part of the design to specify the appropriate t y p e of device.
GN2 Guidance Note 2 provides m o r e comprehensive guidance on this subject. It should b e
consulted and its contents taken into account.
▼ Table 2 . 7 Examples of utilization categories for alternating current installations
Utilization
category
Frequent operation
Infrequent
operation
Typical applications
AC-20a
AC-20b
Connecting and disconnecting under
no-load conditions
AC-21a
AC-21b
Switching of resistive loads,
including moderate overloads
AC-22a
AC-22b
Switching o f mixed resistive and
inductive loads, including
moderate overloads
AC-23a
AC-23b
Switching of motor loads o r other
highly inductive loads
If switchgear to BS EN 60947-1
is suitable for isolation, it will b e marked with the
symbol for isolation (references IEC 60417-6169-1
and IEC 60617-07-01-03)
shown
in Figure 2.2.
▼ Figure 2 . 2 Basic symbol for isolation function
This may b e endorsed with a symbol advising of function, for example, for a switch
disconnector providing isolation as illustrated in Figure 2.3.
▼ Figure 2 . 3 Symbol marked on a switch disconnector providing isolation
Guidance N o t e 3: I n s p e c t i o n & Testing
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Table 537.4 Guidance on the suitability or otherwise of protective, isolation and switching devices
t o be employed for one or more of the functions of isolation, emergency switching
and functional switching is given in Table 537.4 of B S 7 6 7 1 a n d in Guidance Note 2.
The inspector should carry o u t an isolation review to check that effective isolation
can b e achieved, b u t it is n o t the inspector's responsibility t o resolve any apparent
shortcomings
or problems with the isolation and switching design. The review could
include, where appropriate, locking-off and inspection or testing to verify that the circuit
is dead and n o other source of supply is present. The designer should also identify
where it may b e necessary to isolate the neutral conductor.
Note (5) to Table 537.4 i n B S 7 6 7 1 points out that circuit-breakers and RCDsare n o t
intended for frequent load switching or functional switching unless they are approved
by the device manufacturer for this duty. The note gives further guidance relating to
this a n d the inspector is at liberty to make a comment o n this use if it is inappropriate.
543.3.3.101 BS 7671 does not allow a switching or isolating device to b e placed in the earth
or protective conductor, other than a plug and socket-outlet, except for the special
conditions outlined in Regulations 543.3.3.101.
k
Presence of undervoltage protective devices
Suitable precautions should b e in place where a reduction in voltage, or loss and
subsequent restoration of voltage, could cause danger. Normally, such a requirement
concerns only motor circuits. If precautions are required, they will have been specified
by the designer; however, the devices used must b e confirmed as matching the
equipment specification and the relevant regulations in Section 445.
Chap 4: |
Protective a n d monitoring devices
Some protective
devices have user or on-site configurable
settings. The inspector
needs to confirm that the installer has correctly set up such protective devices.
421.1.7 Arc fault detection devices (AFDDs) are designed to provide protection by monitoring
the change of current f l o w in a final circuit due to a possible cable conductor fault
that could cause an arc and possible fire. BS 7671 requires AFDDs t o b e provided for
single-phase AC circuits supplying socket-outlets with a rated current not exceeding
3 2 A in electrical installations for:
(a) Higher Risk Residential Buildings (HRRBs);
Note:
HRRBs are assumed to b e residential buildings over 18 m i n height or in excess
of six storeys, whichever is met first. It is anticipated that i n m a n y areas higher risk
residential buildings will b e defined in legislation which can b e subject to change over
time, as well as in risk management procedures adopted by fire a n d rescue services.
Current legislation should be applied.
(b) Houses in Multiple Occupation
(HMOs);
(c) Purpose-built student accommodation; and
(d) Care homes.
For other installations, BS 7 6 7 1 recommends their use for AC final circuits supplying
socket-outlets not exceeding 3 2 A, but it is for the designer to decide on their use in
other installations, a n d the inspector cannot comment if they are not installed.
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Guidance Note 3 : Inspection
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a n d Technology
of Engineering
2
Some makes of AFDDs have a manual test button (like an RCD) a n d this should b e
pressed at commissioning and user advised to press at six monthly intervals to prove
operation. Other AFDDs have an automatic test facility which will trip t h e device in t h e
event of a malfunction,
this will b e indicated on the device.
Sect 443 The guidance for the application
revised in BS 7671:2018+A2:2022,
of surge protective
devices (SPDs) has been
providing for protection
against switching surges
and surges of atmospheric
origin (lightning
strikes). Except for simple installations
for which t h e requirements
of Sections 443 and 5 3 4 of BS 7 6 7 1 can b e followed,
surge protection, and where applicable lightning protection systems, will usually b e
designed and installed, by specialist suppliers i n accordance with the relevant parts of
BS EN 6 2 3 0 5 . In these cases, the inspector can only review what is installed against
the scheme documentation provided by the specialist suppliers, and review their test
and commissioning documentation.
Sect
m
Labelling of protective devices, switches and terminals
514 8 J Each protective device must b e arranged and identified
so that the circuit protected
514.9.1 can b e easily identified; a diagram or chart indicating t h e function of each circuit and
size of conductors is required. The inspector will need this key document in order to
carry out much of their inspection and testing.
n
Selection of equipment and protective measures appropriate to
external influences
Equipment
must b e selected with regard to its suitability for the environment
at its
specific location —ambient temperature, heat, water, foreign bodies, corrosion, impact,
vibration, flora, fauna, radiation, building use and structure. A careful inspection is
necessary to confirm the suitability of each item of equipment.
°
Adequacy of accessto switchgear and equipment
Sect 513 Every piece of equipment that requires operation or attention by a person m u s t b e
so installed that adequate and safe means of access (related to the amount of its
use) and sufficient working space are afforded. The inspector should check that these
requirements
P
are met.
Warning and instruction notices
Warning and instruction notices, suitably located, are required to b e installed for:
(i) warning of voltage;
(ii) warning of live parts that are not capable of being isolated by a single device;
(iii) periodic inspection and testing;
(iv) periodic user testing of RCDs;
(v) periodic user testing of AFDDs;
(vi) earthing and bonding connections;
(vii) alternative supplies;
(viii) presence of SPDs;
(ix) high protective conductor current; and
(x) the presence of diagrams, instructions or similar information.
Instruction
notices (iii), (iv), (v) and (viii) above need not b e applied for installations
in domestic (household)
premises where t h e information
is recorded as part of t h e
certification for initial verification, complete with the Guidance for Recipients as detailed
in Appendix 6 of BS7671.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
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Appendix 11The minimum size requirements for text o n warning signs and instruction notices have
been revised in Amendment 2 : 2 0 2 2 t o BS 7671:2018, and reference is n o w made to
BS EN IEC/IEEE 82079-1 Preparation o f information for use (instructions for use) o f
products. Principles and general requirements. Warning notices and other safety signs
are additionally required to comply with BS ISO 3 8 6 4 series Graphical symbols. Safety
colours and safety signs and BS EN ISO 7010 Graphical symbols. Safety colours and
safety signs. Registered safety signs. These standards permit far more flexibility in text
sizes than t h e requirements of previous versions of BS7671. Guidance and examples
are provided in Appendix 11.
The warning and instruction notices in Section 514 of B S 7 6 7 1 are discussed below.
514.10.1(j)
Voltage
► Warning notices are required where a nominal voltage exceeding 2 3 0 V to earth
exists within an item of equipment
or enclosure and where the presence of such
a voltage would n o t normally b e expected. An example would b e the use of a
6 9 0 V three-phase AC power transformer used on an American air base located
in the UK. Examples are shown in Figure 2.4.
Note:
In m o s t three-phase 2 3 0 / 4 0 0 V systems, t h e voltage t o Earth is 2 3 0 V. It is n o t
normally necessary in those installations to provide a voltage warning label for
t h e purposes of Regulation 514.10.1.
▼ Figure 2 . 4 Examples of t h e warning notice required b y Regulation 514.10.1
a. general use (font size 14 pt)
/X
WARNING
/ 7 \ 400/690 V
b. use on surfaces less than 1 0 cm 2 (font size 7 pt)
A WARNING
/ 7 \ 400/690 V
514.11.1(jj)
Isolation
► Warning notices are required where live parts are not capable of being isolated
by a single device. The location of disconnectors should also b e indicated, except
where there is n o possibility of confusion.
(iii) Periodic inspection and testing
514.12.1► The wording of t h e required instruction notice is given in Regulation 514.12.1.
Examples are shown in Figure 2.5.
This notice is not required for installations i n domestic (household) premises
where the information
is recorded as part of the certification for initial verification,
complete with the Guidance for Recipients as detailed in Appendix 6 of BS7671.
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▼
Figure 2 . 5 Examples of the instruction notice required by Regulation 514.12.1
a. general use (font size 14 pt)
IMPORTANT
This installation should be periodically inspected and tested
and a report on its condition obtained, as prescribed in BS 7671
Requirements for Electrical Installations.
Date of last inspection
Recommended date of next inspection
b. use on surfaces less than 10 cm2 (font size 7 pt)
IMPORTANT
This installation should be periodically inspected and tested
and a report In its condition obtained, as prescribed in BS 7671
Requirements for Electrical Installations.
_ . ..
„
T S June 2022
Date of last inspection ................................
.777.77
Recommended date of next inspection
(iv)
514.12.2
►
RCDs
T h e w o r d i n g of t h e required instruction
Examples are shown i n Figure 2.6.
This notice
is not required
n o t i c e is given i n Regulation
f o r installations i n domestic
(household)
514.12.2.
premises
w h e r e the i n f o r m a t i o n is r e c o r d e d as p a r t of t h e certification f o r initial verification,
c o m p l e t e w i t h t h e G u i d a n c e for Recipients
as detailed i n Appendix 6 of B S 7 6 7 1 .
▼ Figure 2 . 6 Examples of the instruction notice required by Regulation 514.12.2
a. general use (font size 14 pt)
This installation,
or part of it, is protected
by a
device
which
automatically
switches
off the
supply if a fault develops. Test six-monthly
by
pressing the relevant test button(s) which should
operate
the device.
Afterwards,
manually
switch
o n the device. If the device does not operate,
indicates a fault, seek expert advice.
or
b. use on surfaces less than 10 cm 2 (font size 7 pt)
This installation,
or part of it, is protected by a
device
which
automatically
switches
off the
supply if a fault develops.
Test six-monthly
by
pressing the relevant test button(s) which should
operate the device. Afterwards,
manually switch
on the device. If the device does not operate, or
indicates a fault, seek expert advice.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
43
2
(v)
AFDDs
► Where AFDDs are installed, those provided with a manual test button (as RCDs)
should b e tested every six months by pressing t h e button. An instruction notice t o
this effect should be provided. The text of the RCD notice in Regulation 514.12.2
can b e used (see examples in Figure 2.6). Some AFDDs are self-testing. AFDDs
may b e provided in a single package also containing overcurrent and/or residual
current protective devices.
This notice is not required for installations in domestic (household) premises
where the information is recorded as part of the certification for initial verification,
complete with t h e Guidance for Recipients as detailed in Appendix 6 of BS 7671.
(vi) Earthing and bonding connections
► The requirements for t h e warning notice and its wording are given in Regulation
514.13.1. Examples are shown i n Figure 2.7.
▼ Figure 2.7 Examples of the warning notice required by Regulation 514.13.1
”zz“
Safety Electrical
Safety Electrical
Connection -
Connection -
Do Not Remove
Do Not Remove
BS 7671 permits the notice to b e provided by a clamp complying with BS 951
(Figure 2.8).
▼ Figure 2.8 Example of a warning notice provided on a BS951 clamp
Where protection by earth-free local equipotential bonding (Regulation 418.2.5
refers) or by electrical separation for the supply to more than one item of
equipment (Regulation 418.3 refers), warning notices with t h e wording given in
Regulation 514.13.2 are required. An example is provided in Figure 2.9.
▼ Figure 2.9 Example of the warning notice required by Regulation 514.13.2
The protective bonding conductors in
this location MUST NOT BE
CONNECTED TO EARTH.
Equipment
having
exposedconductive-parts connected to earth
must not be brought into this location
44
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
2
(vii) Alternative supplies
► For installations with alternative or additional voltage sources, a 'multiple-supplies’
warning notice is required at mains positions, points of isolation, distribution
boards and at any remote metering. The wording of t h e notice is given in
Regulation 514.15.1. An example is shown in Figure 2.10.
▼
Figure
2.10 E x a m p l e of the warning
WARNING
Multiple
Supplies
notice
r e q u i r e d by Regulation 5 1 4 . 1 5 . 1
Isolate all electrical supplies
before carrying out work
Isolate primary supply at
Isolate alternative sources at
Solar PV inverter
(outside
wall)
(viii) Presence of SPDs
514.16=1 ►
Regulation 514.16.1 requires a label at or near a distribution board that contains,
or supplies circuits with, SPDs.lt is important to identify where SPDs are in the
installation, as they may b e damaged by insulation resistance tests, o r affect
insulation resistance test results.
This notice is not required for installations in domestic (household) premises
where t h e information is recorded as part of t h e certification for initial verification,
complete with the Guidance for Recipients as detailed in Appendix 6 of B S 7 6 7 1 .
The information may b e clearly marked o n SPDs installed at the distribution board
o r consumer unit. Some SPDs are supplied with a suitable label.
514.17
543.7.1.205
(jx ) High protective conductor current
►
A warning notice must b e provided at the relevant distribution board indicating
circuits that have a high protective conductor current, as required by Regulation
543.7.1.205.
▼
Figure
2.11 E x a m p l e of t h e warning
notice
r e q u i r e d by Regulations 5 1 4 . 1 7 a n d
543.7.1.205
/
<
A
WARNING
7 \
High protective
conductor currents
y
■
The following circuits may have high
protective conductor currents:
Ring
final
circuits
iLl
and
2.L2.
Guidance Note 3: Inspection & Testing
©The Institution of Engineering and Technology
45
2
514.9.1
(x )
Presence of diagrams, instructions and similar information
► The presence of diagrams, charts or tables, or an equivalent f o r m of information
for t h e work being inspected, should b e verified. The form of information
should
b e legible and durable, a n d should indicate all of the following:
(a) t h e t y p e and composition
of each circuit (including t h e points of utilization
served, the number and size of conductors, a n d t h e t y p e of wiring);
(b) the m e t h o d used for compliance with Regulation 410.3.2 (that is, t h e
protective measures used for basic and fault protection);
(c) t h e information necessary for t h e identification of each device performing
t h e functions of protection, isolation and switching, and its location; and
(d) any circuit o r equipment that is vulnerable to the electrical tests as required
by Part 6.
For a simple installation, t h e foregoing information can b e given in t h e f o r m of
a schedule. An additional copy of t h e Schedule of Circuit Details provided within
or adjacent to each distribution board is likely to m e e t this requirement. In
domestic (household) premises or similar installations the schedule does not
have to b e fixed o n o r near the distribution board or consumer unit, provided that
the information is contained
along with t h e certification for initial verification,
complete with Guidance for Recipients according to Appendix 6 of BS7671.
A complex installation would obviously require more comprehensive
information,
in the f o r m of a record or of 'as-built' drawings and O & M documents.
Diagrams, charts, warning and information and instruction notices should comply
with the standards specified in Regulation 514.9.2.
Non-standard colours
Over time, there have been changes in the colours for identification
in BS 7671,
and, before
BS 7671:2001(2004),
1992, previous
editions
of conductors
of the Wiring Regulations. In
awarning notice was introduced for installations using conductor
identification colours to different versions of BS7671. Regulation 514.14.1 was deleted
in BS 7671 :2018+A2:2022 and such a w a r n i n g notice will, in future, n o t b e necessary
t o comply with BS 7671 .
There is nothing to prevent the continued use of this type of warning notice.
q
Erection methods
Chapter 5 2 contains detailed
requirements
on selection
and erection.
Fixings of
switchgear, cables, conduit, fittings, etc. must b e adequate for the environment
and a
detailed visual inspection is required during the erection stages, as well as at completion.
Regulation 521.10.202 requires that cables are to b e supported so they will n o t collapse
and come away f r o m their fixings in the event of a fire and impede the escape of
persons f r o m buildings. This can usually b e achieved by installing a metal cable fixing
at reasonable intervals.
2.5.3
Inspection
checklist
Listed below are requirements to b e checked w h e n carrying out an installation
inspection. The list is not exhaustive. The inspector can check against t h e design and
installation data provided by the designer and installer and report any non-compliances
noted, but cannot make any requirements.
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2
General
(a) Equipment complies with a product standard or equivalent (511.1).
(b) Equipment is installed using good workmanship (134.1.1).
(c) Equipment is accessible for operation, inspection and maintenance (513.1).
(d) Equipment is suitable for local atmosphere and ambient temperature (512.2).
For installations i n potentially explosive atmospheres, the requirements of
BS7671 are supplemented by the requirements or recommendations of other British
or Harmonized Standards or by those of the person ordering the work (110.1.3).
(e) Final circuits are separate, including t h e neutral conductors (314.4).
(f) Protective devices are identified to indicate the circuits they protect (514.8.1).
(g) Protective devices are adequate for their intended purpose, including AFDDs
and SPDs, where installed (Ch. 53).
(h) Disconnection
times for protection
against electric shock are likely to b e met by
installed protective devices (Ch. 41).
(i) All circuits are identified (514.1,514.8,514.9).
0)
Main switch is provided (462.1.201).
(k) Supplies to any safety services are correctly installed, for example, fire alarms
to BS 5 8 3 9 and emergency
lighting to BS 5 2 6 6 (Ch. 56). This does not
include any inspection of the safety systems, which should b e inspected
maintained by specialists.
and
(l) Auxiliary circuits are installed (557).
(m) Means of isolation are labelled (514.1, 537.2.7).
(n) There is provision for disconnecting the neutral (Ch. 4 6 ; 537.2.8).
(o) Main switches t o single-phase installations, intended for use by an ordinary
person, for example, domestic, shops and office premises, are to b e double
pole (462.1.201).
(p) RCDs are provided where required (411.3.3, 411.3.4, 411.4, 411.5, 415.1,
422.3.9, 522.6.201,
703.411.3.3,
522.6.202,
704.410.3.10,
708.415, 708.553.1.14,
532.1, 701.411.3.3, 702.53, 702.55.1, 702.55.4,
704.411.3.2.1, 705.411.1, 705.422.7,
709.531.2,
706.410.3.3,
710.410.3, 710.411.4,710.531.3, 711.410.3.4,
711.411, 712.531.3.5.1, 714.411.3.4, 717.411.6.2, 717.413, 717.415.1, 721.415.1,
722.531.3,
740.410.3, 740.415.1, 753.411.3.2, 753.415.1).
(q) Selectivity between RCDs is considered to avoid danger (314.1,314.2, 531.3).
(r) Main earthing terminal (MET) is provided (542.4.1), is readily accessible and is
identified
where separate from switchgear (514.13.1).
(s) There is provision for disconnecting t h e earthing conductor (542.4.2).
(t) Cables used comply with British or Harmonized Standards and with
Construction
the
Products Regulation (Appendix 4 of BS 7671).
(u) Earth tail pots are installed where required o n mineral-insulated cables (543.2.7).
(v) Non-conductive finishes o n enclosures are removed where necessary to ensure
good electrical connection and, if necessary, made good after connecting (526.1).
(w) There are adequately rated distribution boards. Distribution boards to t h e
relevant parts of BS EN 6 0 4 3 9 or BS EN 61439 may have a rated diversity
factor (RDF) stated by t h e manufacturer for the assembly, or a group of circuits.
For example, if an assembly has an RDF of 0.8, any combination
of outgoing
circuits in the assembly can b e loaded to 8 0 7o of their rated current, provided
the total load o n the outgoing circuits does not exceed the rated current of the
assembly (642.2).
(x) Correct fuses or circuit-breakers are installed (Section 531, Section 533).
(y) All connections are secure (134.1).
(z) Protection is provided against voltage disturbances, including overvoltages,
where required (Ch. 44).
Guidance Note 3: Inspection & Testing
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47
2
(aa) Measures are taken against electromagnetic disturbances, where required
(Ch. 44).
(ab) Overcurrent protection is provided, where applicable (Ch. 43).
(ac) There is suitable proximity (separation or segregation) of circuits (528).
(ad) Label notice for first periodic inspection and test is provided (514.12.1).
(ae) Sealing of the wiring system, including fire barriers (527.2).
(af) Cables and wiring systems are installed and supported such that they will not
b e liable to premature collapse in the event of afire (521.10.202).
(ag) There is a suitable degree of protection (IP Code) appropriate to external
influences when
installed in accordance with the manufacturer's instructions
(522.3.1, 559.3.1).
Switchgear
(a) Meets
requirements of the relevant parts of BS EN 61008, BS EN 61009,
BS EN 60947-2, BS EN 60898, or BS EN 61439, where applicable, or equivalent
(Section 511).
(b) Is securely fixed (134.1.1) and suitably labelled (514.1).
(c) Switchgear assemblies, including consumer units, are complete with,
or
additionally housed in, fire protecting enclosures (421.1.201).
(d) Non-conductive
finishes o n switchgear are removed at protective
connections and, if necessary, made good after connecting (526.1).
conductor
(e) Suitable cable glands and gland plates are used (526.1).
(f) Switchgear is correctly earthed (Ch. 54).
(g) Account has been taken of environmental conditions likely t o b e encountered,
i.e., switchgear is suitable for t h e foreseen environment
(512.2).
(h) Switchgear is suitable as a means of isolation as design, where applicable
(Ch. 46, 537.2).
(i) Need
for isolation, mechanical maintenance,
emergency
switching is m e t where required by design (Ch. 4 6 , 537).
and
functional
(j) Firefighters’ switch is provided where required and labelled for identification
and
operation (537.4).
(k) All connections are secure (526).
(l) Cables are correctly terminated a n d identified (514, 526).
(m) There are n o sharp edges o n cable entries, screw heads, etc., which could
cause damage to cables (134.1.1,522.8.11).
(n) There is adequate access, lighting a n d working space (132.12 and 513.1).
General wiring accessories
(a) Complies with appropriate standards, for example, BS 5 7 3 3 (general accessories)
or BS EN 6 0 6 7 0 - 2 2 (junction boxes) (511.1).
(b) Box or other enclosure is securely fixed (134.1.1).
(c) Metal box or other enclosure is earthed where required (Ch. 54).
(d) There are n o sharp edges o n cable entries, screw heads, etc. which could cause
damage to cables (134.1.1,522.8.11).
(e) Non-sheathed
cables, and cores of cable f r o m which sheath has been removed,
are not exposed outside the enclosure (526.8).
(f) Conductors are correctly identified (514.3).
(g) Bare protective conductors having a csa of 6 m m 2 or less are to b e sleeved
green-and-yellow (514.4.2, 543.3.201).
(h) Terminals are tight a n d containing all strands of the conductors (526).
(i) Cable grip correctly used, or clips fitted to cables, prevent strain o n the
terminals (522.8.5, 526.6).
(j) The current rating is adequate (512.1.2).
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(k) Accessories installed in protected escape routes must n o t compromise t h e
structure’s
fire resistance. The accessories should, where necessary, have any
fire resisting pads installed where these are recommended
by t h e manufacturer
(Section 527, Appendix 13).
Notes:
1 Reference
should
a l s o be m a d e to B S 8 3 0 0 series a n d t h e recommendations
in t h e r e l e v a n t A p p r o v e d D o c u m e n t M of t h e B u i l d i n g R e g u l a t i o n s 2010
W a l e s a n d the
contained
for England a n d
Scottish Building Standards with regard to t h e h e i g h t s a t w h i c h socket-outlets,
switches a n d other controls s h o u l d b e installed, in o r d e r to afford c o m p l i a n c e with B u i l d i n g
R e g u l a t i o n s . See a l s o the I E T publication Electrician's
2
Guidance
o n t h e s e l e c t i o n of protective,
Guide
to the Building
i s o l a t i o n a n d switching
Regulations.
devices
in p r o v i d e d in
T a b l e 537.4 o f B S 7 6 7 1 .
Lighting controls
(a) Lightswitches comply with BS 3 6 7 6 or BS EN 60669-1 (511.1).
(b) Lighting controls are selected for external influences (512.2).
(c) Single-pole switches are connected in line conductors only (132.14.1).
(d) Correct colour coding or marking of conductors is used (514.3).
(e) Exposed-conductive-parts,
for example, metal switch plate or surface-mounted
metal back box, are connected to t h e relevant cpc (Ch. 54).
(f) The current rating, allowing for any capacitive or inductive effects as given in the
design cable ratings, is adequate (512.1.2).
(g)
A device that simultaneously
disconnects all line conductors is provided where
a group of luminaires is divided between
three line conductors of a circuit with
only one c o m m o n neutral (559.5.5).
(h) Switch is labelled to indicate purpose, where this is not obvious (514.1.1).
(i)
There are appropriate controls suitable for the luminaires (559.5.1.206).
( j ) Standard wall accessory/switches are installed beyond zone 2 in a location
containing a bath or shower (701.512.3).
Lighting points
(a) Lights connected via a recognized accessory (559.5.1), batten lampholders or
pendant sets are in compliance with BS EN 6 0 5 9 8 .
(b) Ceiling rose complies with BS 67 (559.5.1).
(c) Luminaire supporting couplers comply with BS 6972 or BS 7001 (559.5.1).
(d) Installation couplers comply with BS EN 61535 (559.5.1).
(e) A recognized connecting device is used for luminaires that d o n o t provide a
device for connection
(f)
of t h e supply (559.5.4).
Track systems comply with BS EN 60570 (559.3.4 and 715.521.1).
(g) Systems for ELV lighting comply w i t h BS EN 60598-2-23 (715.521.1).
(h) Bare conductors of ELV lighting installations comply with all requirements of
Regulation 715.521.106 (715.521.1).
(i)
There
is not
m o r e than one
flex,
unless designed
for multiple
pendants
(559.5.1.202).
( j ) Flex support devices are used and are suitable for the mass suspended (559.5.2).
(k) Switch-lines
are identified (514.3.2 and Appendix 7 of BS 7671). For two-core
switch wires, blue conductors are overmarked with b r o w n or L a t terminations;
for three-, four- or five-core cables, all non-brown line conductors of switch
and intermediate strappers are overmarked at terminations w i t h b r o w n or L.
(l)
Penetrations in fire-rated ceiling are m a d e good. Suitable fire-rated luminaires
used where t h e luminaire traverses fire rated ceilings (527.2.1). Recessed
downlighters should b e checked for thermal damage.
Guidance Note 3: Inspection & Testing
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49
2
(m) Ceiling roses and similar not used for circuits have a supply exceeding 2 5 0 V
(559.5.1.201).
(n) Protection f r o m ultraviolet (UV) radiation (if any) is provided to external wiring
within or passing through a luminaire (559.5.6).
Socket-outlets
(a) Socket-outlets
comply with BS 5 4 6 , BS 1363-2
or BS EN 6 0 3 0 9 - 2 (553.1.3)
and are shuttered for household a n d similar installations (553.1.201).
(b) Where used for electric vehicle charging, socket-outlets
complying with
BS 1363-2 are of a type approved by the socket-outlet manufacturer for such
use (722.55.101.0.201.1).
(c) Mounting height above t h e floor or working
complies
surface suitable (553.1.6)
(Also
with Part M of the Building Regulations and the Scottish equivalent,
where relevant - see Note above).
(d) Polarity is correct (643.6).
(e) If in a location containing a bath or shower, socket-outlets are installed at least
3 m horizontally f r o m t h e bath or shower, w i t h t h e exception of a shaver supply
unit or SELV (701.512.3).
(f) Socket-outlets are suitably protected against external influences
where installed
near sinks and cookers. It is recommended that socket-outlets should b e
installed at least 3 0 0 m m horizontally from t h e edges of a sink or washbasin
(excluding drainer) and at least 1 0 0 m m horizontally f r o m the edge of a h o b or
freestanding cooker (see IET Guidance Note 1: Selection and Erection).
(g) Socket-outlets
are suitably protected
against t h e expected external influences
where mounted in a floor (512.2).
(h) Socket-outlets are not
used to supply a water heater having uninsulated
elements (543.3.1).
(i) Where metal conduit
(including
the accessory box) or earthed cable sheath
or similar is used as a protective conductor, there is presence of an earth tail
between t h e accessory box and the socket-outlet terminal (543.2.7).
(j)
Additional requirement is provided by a 3 0 m A RCD or a risk assessment is
provided for specific non-domestic
(k) Socket-outlets
with
socket-outlets
(411.3.3).
integral universal serial bus (USB) charging provision,
or
other electronic devices such as powerline or wireless local area networking
functionality, comply with BS 1363-2:2016 or BS 1363-2:2016+AI:2018.
Junction boxes, joint box and terminations
(a) All cable joints and terminations
are installed
so that they are accessible for
future inspection (except for soldered, encapsulated, etc. joints or marked
maintenance-free accessory. Some connecting devices must b e contained
in an enclosure meeting
maintenance free (526.3).
t h e manufacturer's requirements to b e classed as
(b) Enclosures of terminals provide suitable protection
against mechanical
damage
(526.7).
Fused connection unit
(a) The rating and fuse are correct (533.1).
(b) The fused connection unit complies with BS 1363-4 (Table 537.4, 559.5.1 vii).
Cooker control unit
(a) The cooker control unit is sited to o n e side and is l o w enough for accessibility
and to prevent flexes trailing across radiant plates (522.2.1).
(b) The cable t o the cooker is fixed to prevent strain on connections
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(522.8.5).
2
Conduit systems
General
(a) Conduit
systems are securely fixed, box lids in place and are adequately
protected against mechanical damage (522.8).
(b) Draw points are accessible (522.8.6).
(c) The recommended quantity
of cables for easy draw is not exceeded during
installation, to avoid causing insulation damage. Adequate boxes are suitably
spaced. This item should b e inspected
during the erection stage, as t h e care
and workmanship of the installer can b e verified (522.8.1 and see Appendix E
of t h e IET On-Site Guide’).
(d) Solid elbows and tees are used only as appropriate (522.8.1).
(e) Unused entries are blanked off where necessary (416.2 and 522).
(f) Conduit system components
comply with a relevant British Standard, depending
o n performance requirements
(g) Conduit
(511.1).
systems are provided
with drainage holes and gaskets as necessary
(522.3.2).
(h) The radius of bends is such that cables are n o t damaged (522.8.3).
(i)
Conduit systems installed in protected escape routes are classed as non-flame
propagating according to BS EN 6 1 3 8 6 (422.2.1).
Rigid m e t a l c o n d u i t
(a) Rigid metal conduit complies with BS EN 61386-21 (521.6).
(b) Rigid metal conduit is connected to the MET (411.4.2, 411.5.1).
(c) Line, neutral and any additional protective conductors are contained in the
same conduit (521.5.1).
(d) Conduit is suitable for wet, damp or corrosive situations (522.3, 522.5).
(e) Conduit is fixed appropriately (522.8 and see Appendix G of Guidance Note 1).
(f) Unpainted ends and scratches, etc. are protected by painting (134.1.1, 522.5).
(g) Ends of conduit are reamed and bushed, where relevant (134.1.1, 522.8).
Rigid n o n - m e t a l l i c c o n d u i t
(a) Rigid non-metallic
conduit complies with
BS EN 61386 series (521.6).
BS 4607,
BS EN 60423
o r the
(b) Ambient and working temperatures are within permitted limits (522.1, 522.2).
(c) Provision is m a d e t o allow for expansion and contraction (522.15.1).
(d) Boxes and fixings are suitable for the mass of luminaire suspended at the
expected temperature (559.5.2).
(e) Conduit is of the 'non-flame
propagating' type (521.6).
Flexible m e t a l c o n d u i t
(a) Flexible metal conduit complies with the BS EN 61386 series (521.6).
(b) A separate protective conductor is provided (543.2.3).
(c) Fixed metal conduit is adequately supported
and terminated
(d) Line, neutral
conductors
and any additional
protective
(522.8).
are contained
in the
same conduit (521.5.1).
Trunking
General
(a) Trunking complies with B S 4 6 7 8 or BS EN 50085-1 (521.6).
(b) Trunking is securely fixed and adequately protected
against mechanical damage
(522.8).
(c) Trunking is selected, erected and routed
to avoid ingress of water and solid
objects (522.3).
Guidance Note 3 : I n s p e c t i o n & Testing
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51
2
(d) Proximity to non-electrical
cause damage (528.3).
services, i.e. sources of heat, smoke, etc. cannot
(e) Internal fire sealing is provided where necessary (requires inspection
during the
erection stage) (527.2.2).
(f) Holes surrounding the trunking are m a d e good (527.2.1).
(g) Band I circuits are partitioned
voltage present (528.1).
(h) Circuits are partitioned
f r o m Band II circuits or insulated for the highest
f r o m Band I circuits or wired in mineral-insulated
metal-sheathed cables (528.1).
(i)
Cables are supported for vertical runs (522.8.5).
( j ) Trunking systems used in protected
escape routes are classed as non-flame
propagating according to BS EN 5 0 0 8 5 (422.2.1).
Metal trunking
(a) Line, neutral and any additional
protective
conductors are contained
in the
same trunking (521.5.1).
(b) Metal trunking is protected against d a m p or corrosion (522.3, 522.5).
(c) Metal trunking is earthed (411.4.2,411.5.1).
(d) Joints are mechanically sound and of adequate continuity (543.2.5).
Rigid non-metallic trunking
(a) Ambient and working temperatures are within permitted limits (522.1, 522.2).
(b) Provision is m a d e to allow for expansion and contraction
(522.15.1).
(c) Trunking is of the non-flame propagating type (521.6).
(d) Cables are secured where necessary to prevent premature collapse in the event
of afire (521.10.202).
Busbartrunking and powertrack systems
(a) Busbar trunking system complies with BS EN 60439-2
or BS EN 61439-6 or
another appropriate standard; the powertrack system complies with B S E N 61534
series or another appropriate standard (521.4).
(b) Systems are securely
fixed and adequately protected against mechanical
damage (522.8).
(c) Joints are mechanically sound and of adequate continuity (543.2.5).
Insulated cables
Non-flexible cables
(a) Non-flexible cables are of the correct t y p e and comply with
Construction Products Regulation design requirements (521).
the
relevant
(b) The current rating is correct (523 a n d Appendix 4).
(c) Non-flexible cables are protected against mechanical damage and abrasion (522.8).
(d) Non-flexible cables are suitable for high or low ambient temperature, as
necessary (522.1).
(e) Non-sheathed cables are protected by enclosure in conduit, duct or trunking
(except for protective conductors of 4 mm 2 and larger) (521.10 a n d 543.1).
(f) Sheathed cables concealed in a wall at a depth of less than 5 0 m m f r o m the
surface and n o t forming part of a SELVor PELV circuit:
(1) are routed in prescribed zones, with additional protection
provided
by an
RCD having a rated residual operating current, l£ n , not exceeding 3 0 m A ; or
(si) are provided with mechanical protection
complying with (522.6.204).
(g) Cables concealed in a partition containing metallic structural parts:
(i)
are provided
with
exceeding 3 0 m A ;
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Guidance Note 3: inspection & Testing
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additional protection by an RCD having
a lAn not
2
(ii) are provided
with
adequate
mechanical protection to
suit
both
the
installation of t h e cable and its normal use; or
(Hi) comply with the requirements set out in Regulation 522.6.203 (522.6.202).
(h) Cables exposed to direct sunlight are of a suitable t y p e or are suitably shielded
(522.11).
(i)
Non-flexible cables are not run in lift or hoist shaft unless they are part of the
lift installation a n d of the permitted type (528.3.5).
( j ) Cables in protected escape routes should b e of t h e permitted types with regard
to fire and smoke performance (422.2.1).
(k) Cables buried in the ground are correctly selected and installed for use (522.8.10).
(l) Cables installed overhead are correctly selected and installed for such use (522.8.4).
(m) The internal radius of every bend in a wiring system should be such that it is not so
tight that the cable and/or its conductors suffer damage and such that terminations
are not in any way stressed (522.8.3 and Appendix G of Guidance Note 1).
(n) Non-flexible cables are correctly supported and secured where necessary to
prevent premature collapse in t h e event of a fire (521.10.202, 522.8.4, 522.8.5).
(o) Non-flexible cables are n o t exposed to water, etc. unless they are suitable for
such exposure (522.3).
(p) Metal sheaths and armour are earthed (411.3.1.1).
(q) Conductors are identified at terminations (514.3).
(r) Joints and connections are electrically and mechanically sound and adequately
insulated (526.1, 526.2).
(s) All wires are securely contained in terminals, etc. without strain (522.8.5, 526).
(t)
Terminals are enclosed (526).
(u) Glands are correctly selected and fitted with shrouds and supplementary earth
tags as necessary (526.1).
(v) Joints and connections are mechanically sound and accessible for inspection,
testing and maintenance purposes, except as permitted otherwise (526.1, 526.3).
Flexible cables
(a) Flexible cables are of the correct type and comply with the relevant design
requirements of t h e Construction Products Regulation (521.9.1).
(b) Current rating is correct (523 and Appendix 4).
(c) Cables are protected where exposed t o mechanical damage (522.6, 522.8).
(d) Cables are suitably sheathed where exposed to contact with water (522.3)
or
corrosive substances (522.5).
(e) Cables are protected where used for final connections to fixed apparatus, etc. (526.8).
(f) Cables are selected for resistance to damage by external heat sources (522.2).
(g) There is segregation of Band I and Band II circuits (528; see also BS 6701 and
B S E N 50174 series).
(h) There is segregation of fire alarm and emergency lighting circuits (528; see also
BS 5839, BS 5266).
(i)
Cores are correctly identified
(514.3).
(j) Connections have durable electrical continuity,
adequate mechanical strength
and are made using appropriate means (526.1, 526.2).
(k) Where used as fixed wiring, the relevant requirements are m e t and cables are
secured where necessary to prevent premature collapse in the event of a fire
(521.9.1, 521.10.202).
(l)
Final connections
to current-using equipment
are properly secured and arranged
to prevent strain o n connections (526.6).
(m) Mass is supported by cable so as not to impair safety of the installation (559.5.2).
Guidance Note 3: Inspection
& Testing
© The Institution of Engineering and Technology
53
2
Protective c o n d u c t o r s
(a) Cables incorporating protective
Harmonized
(b) Joints in
conductors
comply with the relevant British or
Standard (511.1).
metal conduit,
ducting or trunking comply with
Regulations for
preservation of continuity (543.3).
(c) Flexible or pliable conductive conduit is supplemented by a protective conductor
except where only SELV systems are enclosed by the conduit (543.2.3).
(d) Protective conductors have a suitable m i n i m u m csa (543.1).
(e) Protective conductors with a csa of 6 mm 2 o r less are protected by insulation or
equivalent, unless they are part of a multicore cable, o r f o r m part of a conductive
containment
system or enclosure used as a protective conductor (543.3.201).
(f) A cpc at the termination of sheathed cables is protected by sleeving (543.3.201).
(g) A bare cpc is protected against mechanical damage a n d corrosion (543.3.1).
(h) Insulation, sleeving and terminations are identified by t h e bi-colour combination
green-and-yellow (514.4.2).
(i)
Joints are electrically and mechanically sound (526.1).
( j ) Separate cpcs of not less than 4 m m 2 if not protected against mechanical
damage and is not an integral part of a cable, n o t formed by conduit, ducting or
trunking, nor contained in an enclosure formed by a wiring system (543.1.1).
(k) Main and supplementary protective bonding conductors are of the correct size (544).
(l) Cables are secured where necessary to prevent premature collapse in the event
of a fire (521.10.202)
Enclosures
General
(a) There is a suitable degree of protection (IP Code in BS EN 6 0 5 2 9 ) appropriate
to external influences w h e n installed, taking account of the manufacturer's
instructions (416.2, 512.2, 522, Part 7).
2.6
Tests associated with
initial
verification
The test methods described in this section are recommended to b e used as part of
initial and periodic verification. This does n o t rule out the use of other test methods,
provided they give valid results.
Note:
In medical locations of group 1 and 2, the measurement and recording of
supplementary bonding conductor resistance values is required. Where medical
IT systems are installed, measurement of capacitive leakage currents are required.
Further information is available in IET Guidance Note 7 Special Locations.
2.6.1
Test results
The test results must b e recorded o n the Schedule(s) of Test Results and compared
with relevant criteria. For example, in order to verify disconnection times, the relevant
criteria would b e design EFLIvalues provided by t h e designer.
A model Schedule of Test Results is shown in Section 5.
54
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
2
2.6.2
Electrical
Installation
Certificate
(EIC)
Regulation 644.1 of BS 7 6 7 1 requires that u p o n completion of the verification of a
new, modified or extended installation, an EIC based on the model given in Appendix 6
of BS7671 is provided to the person that ordered the work. Chapter 6 4 requires that:
644.3
(a) the EIC is accompanied
644.3
644.,:
(b) the Schedule of Test Results shall include test results for the work done;
by a Schedule of Inspections, Circuit Details and Test
Results. These schedules shall b e based o n the models given in Appendix 6 of
BS 7671;
(c) the EIC is signed or otherwise authenticated
each facet of design, construction
by a skilled person responsible for
and inspection and test and competent to
verify that the requirements of B S 7 6 7 1 have been met; and
644.1.
(d) any defects or omissions revealed by the inspector are required to b e made
good by the installer, and, as necessary, inspected
EIC is issued; it is not the responsibility
and tested again, before the
of the person or organization carrying
out t h e inspection and testing to make good defects or omissions.
Where the installation work does not extend to the installation
of a n e w circuit, a
MEIWC may b e used instead of the full EIC. This simplifies the documentation for small
works; in addition, the required installation inspection and testing and tests are limited
to the circuit being extended or modified, as detailed in Part 4 of the certificate. See
Section 5 for further details and guidance o n the completion
of this certificate.
NOTE:
The model the model forms in Appendix6 of BS7671 can be amended to suit the
installation, provided that the minimum information required is included.
2.6.3
Model
forms
Typical forms for use when
carrying out inspection
and testing are included
in
Section 5 of this Guidance Note.
643.1
2.6.4
T h e sequence of tests
Tests associated with initial verification should b e carried out in the following sequence,
where relevant and practical:
(a) continuity
of protective
conductors, including main a n d supplementary
bonding
(see Section 2.6.5) (Regulation 643.2.1);
(b) continuity of ring final circuit conductors (see Section 2.6.6) (Regulation 643.2.1);
(c) insulation resistance (see Section 2.6.7) (Regulation 643.3);
(d) protection by SELV.PELVor by electrical separation (see Sections 2.6.8 and 2.6.9)
(Regulations 643.4, 643.4.1, 643.4.2);
(e) insulation resistance of non-conducting floors and walls (see Section 2.6.11)
(Regulation 643.5);
(f) polarity (Section 2.6.12) (Regulation 643.6);
(g) protection by ADS (Section 2.6.15) (Regulations 643.7, 643.7.1,643.7.2, 643.7.3);
(h) earth electrode resistance (Section 2.6.13) (Regulation 643.7.2);
(i) EFLI (Section 2.6.15) (Regulation 643.7.3);
( j ) prospective fault current (Section 2.6.16) (Regulation 643.7.3.201);
(k) additional protection (Section 2.6.18) (Regulation 643.8);
(l)
check of phase sequence (Section 2.6.17) (Regulation 643.9);
(m) functional testing (Sections 2.6.18 a n d 2.6.19) (Regulation 643.10); a n d
(n) verification of voltage drop (Section 2.6.20) (Regulation 643.11).
Guidance N o t e 3: Inspection & Testing
© The Institution o f Engineering and Technology
55
2
▼ Figure 2.12 Sequence of tests for initial verification
Regulation
Group
Test description
Section in this
Guidance Note
643.2
Continuity of protective conductors, including main
earthing conductor, and main and supplementary
protective bonding conductors
2.6.5
643.2
Continuity of ring final circuit conductors
2.6.6
643.3
Insulation resistance
2.6.7
643.4
Protection by SELV, PELV or electrical separation
2.6.8
2.8.9
643.5
Insulation resistance of non-conducting floors and
walls (rarely required)
2.6.11
643.6
Polarity
2.6.12
2.6.14
643.7
Protection by automatic disconnection of supply.
Test as relevant:
• Earth electrode resistance'
• Earth fault loop impedance
• Operation of RCDs
2.6.13
2.6.15
2.6.18
Prospective fault current
2.6.16
Additional protection. A test is required to verify the
operation of RCDs used for additional protection
643.9
Check of phase sequence
2.6.17
643.10
Functional testing
2.6.18
2.6.19
643. 1 1
Verification of voltage drop
2.6.20
Safety considerations
0®
Regulation 643.1 requires
the tests in Regulations
643.2 to 643.6 inclusive
tests to be conducted
(where relevant for the
particular installation) in
the order shown, prior to
the installation being
energized.
It is strongly recommended
to address any
unsatisfactory conditions
discovered during a test,
before proceeding with any
subsequent tests.
* Where present,
Regulation 643.1 requires
earth electrode resistance
to be measured prior to
energization.
These tests may involve
parts of the installation
being energized,
depending on the test
method adopted.
643.2 2.6.5 Continuity of protective conductors, including main and
supplementary bonding
Regulation 411.3.1.1 requires installations that provide protection against electric shock
using ADS to have a cpc run to and terminated at each point in t h e wiring and at
each accessory. An exception to this is m a d e for a lampholder having n o exposedconductive-parts and suspended f r o m such a point.
Regulation 643.2.1 requires that a continuity check b e carried out o n all protective
conductors.
This includes the earthing conductor, the protective
conductors
of all
circuits, all main protective bonding conductors and, where applicable, all supplementary
bonding conductors.
Regulation 643.2.1 also requires that a continuity check b e carried out o n each
conductor of every ring final circuit, including the line, neutral and protective conductors.
There are two widely used test methods that have evolved for checking protective
conductor continuity.
method
Test method 1 uses the circuit cable shorted o u t and test
2 uses a supplementary
length of test cable (this method being popularly
known as t h e 'wandering lead' method).
56
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2
Instrument:
use a low-resistance ohmmeter
The relevant conductors, mentioned
for these tests (see Section 4.3).
above, should b e tested to verify that they are
electrically sound and correctly connected.
Test method 1, detailed in this item, as well as checking the continuity of the protective
conductor, measures (R 1 + R2) which, when added to the external impedance (Z e),
enables the EFLI(Z S) to b e checked against the design (see Sections 2.6.14 and 2.6.15).
(R 1 + R2) is the sum of the resistances of the line conductor, Ri, and the cpc, R2 .
Test readings may b e affected by parallel paths through exposed-conductive-parts
and/or extraneous-conductive-parts.
Parallel earth paths and effects on test readings
Inspectors should always b e aware of t h e possible existence of parallel earth return
paths. These may take t h e f o r m of metallic cable management products, extraneousconductive-parts
or, indeed, other metallic parts. Examples include installations
incorporating steel conduit, steel trunking, mineral-insulated copper-clad cable (MICC),
steel wire armoured (SWA) or other metal-sheathed
cables, equipment
and accessory
boxes fitted to metal stud walls or to the building fabric, and luminaires fitted in grid
ceilings. Such parallel paths exist in domestic, commercial and industrial installations.
The effect of parallel earth return paths is that the measured
value of protective
conductor continuity, R2) tends towards zero. It is often impractical and, in some cases,
impossible to carry out testing with some or all of the parallel paths disconnected and
the inspector must b e aware of this.
Test m e t h o d 1 (for circuits)
Make a temporary shorting link of cable and connect the line conductor to the protective
conductor at the distribution board or consumer unit. Then test between line and earth
terminals at each outlet i n the circuit, as shown in Figure 2.13. The resistance of the
test leads should either b e measured and deducted f r o m t h e readings obtained, or
auto-nulled by the test instrument,
which most m o d e r n instruments
are able to do.
Where the installation has all-insulated wiring (see notes o n parallel earth paths and
effects o n test results above) and the cable accessories are not in contact with earth,
then this test measures(Ri + R2), i.e. the resistance of the line conductor, R i plus the
resistance of t h e protective conductor, R2 , for that circuit which, if added to the EFLI
at the distribution board, can b e taken as t h e circuit's EFLI.lt is important to record
t h e value of (R 1 + R2) obtained at the circuit's extremity, namely the furthest circuit
distance f r o m t h e distribution
board.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineering and Technology
57
2
▼ Figure 2.13 Connections for testing continuity of protective conductors: test method 1
OoUT*
Temporary
link
■; ©
ir
*®1
;
voiw
Phw
Main switch off, secured by safety locking device.
All fuses removed, circuit breakers off.
Zero instrument across test link.
Note: remember to remove temporary link after test.
Many electronic or electromagnetic
control devices present an open-circuit
when the
l o w voltage AC power is removed. Examples may include, but are n o t limited to, the
following types of product:
(a) contactors;
(b) motion and day/night controls;
(c) energy control timers;
(d) lighting dimmers;
(e) remote or smart technology switches; and
(f) building management system controllers.
Figure 2.14 shows a n alternative approach to test method
1 , that can b e used to test
protective conductors downstream of a control device which is open-circuit when low
voltage AC power is removed. This test approach simply measures (R n + R2) instead
o f ( R 1 + R2).
▼ Figure 2.14 Alternative approach for testing continuity of protective conductors: test
method 1, for circuit conductors downstream of electronic control devices
Electronic
control device,
for example a
dimmer
Temporary link
•© ■© >©
AUTO|
VO»W
PhiM
Main switch off, secured by safety locking device.
All fuses removed, circuit breakers off.
Zero instrument across test link.
Note: remember to remove temporary link after test.
58
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
2
Expected results for test method 1
The
results
should
f i r s t a n d f o r e m o s t indicate
conductors.
For insulated
a n d similar
a r e not
m a y b e earthed,
n o discontinuity
wiring systems i n s t a l l e d i n conditions
c o n n e c t e d to the
f a b r i c of the
t h e n a s s t a t e d earlier, the
readings
building
i n the
where
protective
a c c e s s o r y boxes
or other
elements
m e a s u r e d will b e the
that
sum
of
t h e l i n e a n d p r o t e c t i v e c o n d u c t o r resistances ( R 1 + R2) . T h i s t e s t c a n d e t e c t p o o r
c o n t i n u i t y a t j u n c t i o n s a n d c o n n e c t i o n s as, f o r a n e w i n s t a l l a t i o n w i t h n e w accessories,
t h e contribution of resistance of healthy c o n n e c t i o n s to t h e m e a s u r e d resistance is
negligible
a n d c a n be ignored.
conductors
given
Thus,
by employing
in A p p e n d i x B of this Guidance
circuits c a n b e approximated,
t h e resistance
Note,
expected
data f o r copper
v a l u e s for healthy
a n d c o m p a r e d with the test readings
obtained.
a b o u t 5 5 m w i t h 2.5 mm 2 l i n e a n d 1 . 5 m m 2
As a n e x a m p l e , a radial c i r c u i t of length
p r o t e c t i v e c o n d u c t o r s s h o u l d h a v e a n ( R 1 + R2) r e s i s t a n c e as f o l l o w s :
Length
o f circuit is 5 5 m
Resistance
p e r metre
of the line a n d protective
c a b l e is 19.51 mQ/m
(at 20 °C) f r o m Table B l
T h e o r e t i c a l minimum
DC r e s i s t a n c e = (55
conductors
x 19.51 )/l, 000
i n a 2.5 mm 2 /1.5
mm2
= 1.07 Q
W h e n v e r i f y i n g a circuit, t h e i n s p e c t o r s h o u l d t a k e i n t o a c c o u n t t h a t a h i g h e r v a l u e
m i g h t b e m e a s u r e d , as t h e r e will b e s o m e resistance at t h e terminations, a n d t h e r e
m a y b e a c o n t a c t r e s i s t a n c e f o r c o n n e c t i o n of p r o b e s a n d clips, t h a t c a n i n c r e a s e with
c o r r o s i o n on o l d e r terminals.
might
a l s o contribute
Switches,
to a higher
fuses,
a n d other
t y p e s of protective
device,
reading.
Test method 2 (for circuits)
Instrument:
u s e a l o w - r e s i s t a n c e o h m m e t e r f o r t h i s t e s t (see S e c t i o n 4.3).
O n e l e a d of t h e t e s t i n s t r u m e n t is c o n n e c t e d t o t h e e a r t h t e r m i n a l a t t h e d i s t r i b u t i o n
b o a r d v i a a length
of test c a b l e or ' w a n d e r i n g lead'.
make contact
with the protective
f o r example,
a t luminaires,
2.15. T h e resistance
conductor
switches,
of the wandering
d e d u c t e d f r o m t h e r e a d i n g s obtained,
The other
test
lead
at various p o i n t s o n the circuit
f u s e d connection
is used
under
units, etc. a s shown
l e a d a n d t h e test l e a d s a r e either
to
test,
in Figure
measured a n d
or a u t o - n u l l e d by the test instrument,
which
m o s t m o d e r n i n s t r u m e n t s a r e a b l e t o do.
This test m e a s u r e s the resistance of the cpc, R 2 , w h i c h should
b e recorded o n the Schedule
of Test Results (see notes on parallel earth paths and effects o n test readings above).
G u i d a n c e Note 3: I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
59
2
▼ Figure 2 . 1 5 Connections for testing continuity of protective conductors: test m e t h o d 2
wander-lead
Main switch off, secured by safety locking device.
All fuses removed, circuit breakers off.
Zero instrument through wander-lead.
Expected results for test method 2
The
results
should
f i r s t a n d f o r e m o s t indicate
c o n d u c t o r s . For insulated
w i r i n g systems
n o discontinuity
in the
protective
i n s t a l l e d in c o n d i t i o n s w h e r e a c c e s s o r y boxes
a n d s i m i l a r a r e not c o n n e c t e d t o t h e f a b r i c o f t h e b u i l d i n g o r o t h e r e l e m e n t s t h a t
m a y b e e a r t h e d , the measurement
w i l l equate
to the protective
conductor
resistance,
R 2 . T h i s test c a n d e t e c t p o o r c o n t i n u i t y at j u n c t i o n s a n d c o n n e c t i o n s as, f o r a n e w
installation w i t h n e w accessories, t h e c o n t r i b u t i o n o f r e s i s t a n c e o f h e a l t h y c o n n e c t i o n s
i s negligible
a n d c a n b e ignored.
c o n d u c t o r s given
Thus, by employing
the resistance
in A p p e n d i x B of this G u i d a n c e Note,
data f o r c o p p e r
e x p e c t e d values for healthy
cable a n d connections c a n b e checked.
As a n e x a m p l e , a radial circuit of length
a b o u t 5 5 m with a 2 . 5 mm 2 c o p p e r p r o t e c t i v e
c o n d u c t o r s h o u l d h a v e a n R2 r e s i s t a n c e a s f o l l o w s :
Length
of c i r c u i t i s 5 5 m
Resistance of a 2.5 mm 2 conductor
is 7.41 m Q / m
(at 20 °C) f r o m Table B l
T h e o r e t i c a l m i n i m u m D C r e s i s t a n c e = (55 x 7.41)71,000
W h e n v e r i f y i n g this circuit,
the inspector
i n t h e o r d e r of, say, 0.4 Q
to 0.5 Q . If t h e circuit
protective conductor
s h o u l d b e looking
is broken and connected
= 0.41 Q
f o r a reading
h a s several outlets,
somewhere
m e a n i n g that the
i n screw terminals a t each accessory, then a
slightly higher value may be measured, a s there will be some resistance at the terminations.
Testing bonding conductors and earthing conductors
To c o n f i r m the continuity
of t h e s e protective
conductors,
test
method
2 is u s e d . In
m e d i c a l l o c a t i o n s o f G r o u p 1 a n d 2 it is n e c e s s a r y t o m e a s u r e a n d r e c o r d the v a l u e s
of t h e s u p p l e m e n t a r y b o n d i n g c o n d u c t o r s . A c c o u n t s h o u l d b e t a k e n of t h e p o s s i b i l i t y
of test readings
being
a f f e c t e d by parallel paths,
as m e n t i o n e d earlier in this section.
For t h i s r e a s o n , it m a y b e n e c e s s a r y t o carry o u t t h e test w i t h the p r o t e c t i v e c o n d u c t o r
d i s c o n n e c t e d a t o n e end, w h e r e p r a c t i c a b l e .
60
G u i d a n c e Note
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© The Institution of Engineering and Technology
2
This method can also be used to confirm a bonding connection between extraneousconductive-parts where it is not possible to see a bonding connection, for example,
where bonding d a m p s have been ’built in'. The test would b e d o n e by connecting
the leads of the test instrument between any t w o points, such as metallic pipes, and
looking for a suitably l o w reading taking into account the length of the protective
bonding conductor(s). Keep in mind, however, that 15 m of single-core
6.0 m m 2 or
2
2 5 m of single-core 10.0 m m conductor has a resistance of approximately 0.05 Q .
With such low resistances being measured, t h e resolution of the test instrument may
not permit an accurate reading to b e obtained (see Section 4.3) and therefore where
t h e expected resistance is less than 0.1 Q including contact resistances, a value n o t
exceeding 0.1 Q should b e used as a guideline acceptable reading. It should b e noted
that this is not the R2 resistance measured f r o m the MET to the bonding clamp or
adjacent pipework.
To verify that there is a low resistance connection to the actual extraneous-conductivepart itself, t h e measured resistance to the terminal of a bonding clamp can be compared
with t h e measured resistance to the extraneous-conductive-part
itself some distance
f r o m the clamp. An example of this method is shown in Figure 2.16.
Where metallic enclosures have b e e n used as t h e protective conductors, for example,
conduit, trunking, SWA, etc., the following procedure should b e employed:
(a) inspect t h e enclosure along its length for soundness of construction;
and
(b) perform the standard continuity test using the appropriate test m e t h o d
described above.
Instrument’, use a low-resistance ohmmeter
for this test (see Section 4.3).
▼ Figure 2 . 1 6 Example o f testing t h e effectiveness of a b o n d i n g clamp
Main switch off, secured by safety locking device.
All fuses removed, circuit breakers off.
Zero instrument through wander-lead.
©■©©©©©© ©©©©©
_N® N®] n@|' N®r n@;
First, test at the main
protective bonding
conductor termination
<@ '© <© p© I’© ' © ; ' © ’ © ’ ©
wander-lead
Then, test at exposed-conductive-part
approximately 0.5 m to 1 m from the
bonding clamp. The measurements should
be roughly the same if there is a good
connection between clamp and extraneousconductive-part.
□.□So
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
61
2
Expected test results
The results should first and foremost indicate no discontinuity in the protective
conductors. For lengths of conductor, use Appendix B of this Guidance Note for
resistance data. For joints across bonds by earth clamps and similar, the readings
should approach 0.05 Q , taking into account t h e resolution of the instrument,
its
accuracy at low values and contact resistance.
2.6.6 Continuity of ring final circuit conductors
A three-step test is required to verify t h e continuity of t h e line, neutral and protective
conductors a n d the correct wiring of every ring final circuit. The test results show if t h e
ring has b e e n interconnected
to create an apparently continuous ring circuit, which is
i n fact broken or connected as a ’figure of eight' configuration.
Instrument', use a low-resistance ohmmeter
for this test (see Section 4.3).
Step 1
The line, neutral and protective conductors are visually identified at the distribution
board or consumer unit and t h e end-to-end
resistance of each is measured separately
(see Figure 2.17).
▼ Figure 2.17 Connections for ring final circuit continuity testing: step 1
b. measure rn
a. measure r-i
c. measure r2
|e
These resistances are referred t o as n, rn and r 2, respectively. A reading that indicates
a n o p e n circuit, or resistance higher than the continuity
measurement
range, shows
there is likely to b e a damaged conductor, or an issue with the integrity of connections
or terminations, along t h e ring conductors under test. The resistance values obtained
should b e of t h e same order if the conductors are of the same length, csa and material.
If t h e protective
conductor has a reduced csa, the resistance r 2 of the protective
conductor loop will b e proportionally higher than that of the line or neutral loop.
Because the resistance of a cable is inversely proportional to t h e area, w e can calculate
h o w m u c h w e have t o multiply t h e measured value of r i by to obtain the expected
value of r2 using the following formula:
i
r
__ csa cpc
2- — ~
csa
62
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
line
x
_ csa line x r
2
csacpc
2
For example, for 2.5 m m 2 /1.5 m m 2 cable:
r
2=T3
x r
2=
1
-6 7 x r
2
If the resistance readings are not as expected, this could mean the following:
(a) readings lower than the expected resistance would suggest that the ring is
incorrectly configured, possibly wired in a 'figure of eight’ connection; this may
be further confirmed by the step 2 test below; or
(b) readings higher t h a n the expected resistance would suggest an issue with
the integrity of one or more conductor terminations.
The 'expected resistance' is that found from the tabulated DC resistance for the
conductor csa per metre, multiplied by the installed length and corrected for ambient
temperature. A small allowance should be made for instrument errors. Table B i gives
values of DC resistance for conductors.
Step 2
The open ends of the line and neutral conductors are then connected together so that
the outgoing line conductor is connected to the returning neutral conductor, and vice
versa (see Figure 2.18).
▼ Figure 2.18 Connections for ring final circuit continuity testing: step 2
neutral
fl
I
connector blocks
The resistance between line and neutral conductors is measured at each socket-outlet.
The readings at each of the socket-outlets connected to the ring should be substantially
the same and the value will be approximately one-quarter of the resistance of the line
plus the neutral loop resistances, i.e. (ri + rn)/4 (see mathematical explanation in
Figure 2.19). Any socket-outlets wired as spurs will indicate a higher resistance value,
due to the resistance of the spur conductors.
Note:
Where single-core cables are used, care should be taken to verify that the line and
neutral conductors of opposite ends of the ring circuit are connected together. An
error in this respect will b e apparent from the readings taken at the socket-outlets,
progressively increasing in value as readings are taken towards the midpoint of the
ring, then decreasing again towards the other end of the ring. Where such behaviour
in readings is between particular points part way round the ring, this may indicate an
interconnection within the ring.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
63
▼ Figure 2.19 Mathematical explanation for step 2 (live conductors having the same csa)
Figures 2.19a to e explain t h e expected results for a correctly wired ring circuit.
a
Origin
Testpoint Afor
mathmatical explanation
Open loop resistance = 0.6 O
Figure a above is an example of a correctly wired ring, with the open loop resistances
of t h e line and neutral conductors f r o m step 1 , each being 0.6 O . A test point about a
third distance round t h e ring is used to illustrate t h e maths, as explained below.
b
Origin
0.2 0
t
Test point A
0.4Q
Figures b and c show the resistances of each leg of the ring as a test is applied at this
point as per step 2 (line-neutral).
c
Test
Ni
0.2(1 E° i n t A
T?
0 2(1 /
N z 0.4(1
L 2 0.4(1
□.3Qq
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
2
The equivalent connects are then represented in Figure d.
0.2 fl F
Test
point A
cross-connections
at consumer unit
n2
0.4 fl F
The equivalent circuit diagram and resultant resistance are shown in Figure e .
0.2 0
0.4 0
0.6 0
0.4 0
0.2 0
0.6 0
In summary, the open loop resistances are 0.6 0 for both line and neutral, giving an
C i + rn) value of (0.6 + 0.6), or 1 . 2 0 .
From Figure e above, it can b e seen that a correctly connected ring will give a step 2
reading of a quarter of the (rj + rn) value, or:
Rste P 2 tes t =
£
4
£
. i n t h i s case
= 0 . 3 fl
Step 3
The open ends of the line conductor and cpc are then cross-connected (see Figure 2.20).
▼ Figure 2.20 Connections for ring final circuit continuity testing: step 3
connector blocks
The resistance between line and cpc is measured at each socket-outlet.
obtained
at each of the socket-outlets
The readings
wired in the form of a ring will depend o n
whether the cpc is the same csa and material as t h e line conductors:
Guidance Note 3: Inspection & Testing
© The Institution
of Engineering
and Technology
65
2
(a) Where the cpc is the same copper-equivalent
csa as the line conductors,
the
readings will b e substantially the same and t h e value will b e approximately
one-quarter of the resistance of the line plus cpc loop resistances, i.e.
(r] + rn)/4 (the explanation for this being similar to that for step 2).
(b) Where the cpc has a different csa f r o m the line conductors, for example where
flat twin-and-earth cable is used, the resistance will increase as t h e tests move
around t h e ring f r o m t h e origin of t h e circuit, to a maximum
of approximately
C i + r 2 )/4 at the mid-point of the ring, and decrease as the test point moves
back towards the origin of the circuit. The maximum a n d minimum values
expected during the test are shown in Table 2.8 (see IET Electrical Installation
Design Guide for a comprehensive mathematical explanation).
A higher resistance value will b e recorded at any socket-outlets or other accessories
wired as spurs.
The highest value recorded represents the maximum (R] + R£) of the circuit and is
recorded o n the Schedule of Test Results. The value can b e used to determine
the
EFLI (Z s) of the circuit to verify t h e provisions for automatic disconnection of supply
(see Section 2.6.14).
411.3.2.5
4193
The inspector is again reminded to take note of t h e effects of possible parallel return
paths o n these continuity tests, as described in Section 2.6.5 o f this Guidance Note.
In addition, where supplementary
protective equipotential
bonding is used in
accordance with Regulations 411.3.2.4 and 419.3, this may also affect the readings for
step 3. Examples of circuits which may b e affected in this way include distribution circuits
and final circuits supplying central heating systems, electric showers, or water heaters.
▼ T a b l e 2.8 Variation in reading during tests around t h e ring in Step 3 where line and cpc
have different csa
a General case
Lowest reading
(notes 3 and 4)
csa of line
conductor and
cpc
2.5 m m 2 live
conductors,
1.5 m m 2 cpc
(note 1 )
4.0 mm 2 live
conductors,
1.5 mm 2 cpc
(note 1)
2.5 m m 2 live
conductors,
1.0 mm 2 cpc
(note 2)
G u i d a n c e Note
Percentage difference
between lowest and
highest reading
6 7 o o f highest reading
O.S4X
20 7 o o f highest reading
0.80 x'(r i + r
4
0.82 x
Other
combinations
66
Highest reading
(notes 4, 5 and 6)
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
ri+r z
18 7 o o f highest reading
-
(£1Z£2 I 2
Ri+rJ
x 100 % of highest reading
2
b By length of 3 0 A or 3 2 A ring final circuits u p to the maximum lengths shown i n
Table7.1(i) of the lETOn-Site Guide, with automatic disconnection provided by RCD
4.0 mm 2 live conductor,
1.5 mm 2 cpc
2.5 mm 2 live conductors,
1.5 mm 2 cpc
Total ring
length (m)
Minimum
reading (Notes
3, 4 and 6)
Maximum
reading (Notes
4, 5 and 6)
Minimum
reading (Notes
1, 4 and 6)
Maximum
reading (Notes
4, 5 and 6)
10
0.05
0.05
0.03
0.04
20
0.09
0.10
0.07
0.08
30
0.14
0.15
0.10
0.13
40
0.18
0.20
0.13
0.17
50
0.23
0.24
0.17
0.21
60
0.28
0.29
0.20
0.25
70
0.32
0.34
0.23
0.29
80
0.37
0.39
0.27
0.33
90
0.41
0.44
0.30
0.38
100
0.46
0.49
0.33
0.42
106
0.49
0.52
0.35
0.44
110
0.37
0.46
120
0.40
0.50
130
0.43
0.54
0.47
0.58
150
0.50
0.63
160
0.53
0.67
170
0.57
0.71
171
0.57
0.71
140
Not oossiblo fnoto 81
Notes:
1
2
3
4
5
6
7
8
UK cable type 6242Y to BS 6 0 0 4 or type 6242B to BS 721 1 :2012+AI:2020.
Flat twin and earth cables manufactured between approximately 1969 and 1981.
The lowest reading should occur at the origin of the circuit.
Ignoring measurement error.
The highest reading should occur at the midpoint of the ring, although there may not b e
a socket-outlet or other accessory installed at that point, at which a measurement can
b e made.
Ignoring spurs from the ring.
See IET Electrical Installation Design Cuide for an explanation of the data provided in
this table.
Exceeds maximum length of circuit due to excessive voltage drop.
643.3 2.6.7
Insulation
resistance
Insulation resistance testing is a fundamental
construction
test for inspectors. Often, o n larger
sites, cables will b e insulation resistance tested during various stages of
installation, to prove the integrity of installed cables. It is always preferred to re-test
cables and equipment for insulation resistance as part of initial verification, as well
as during construction. BS 7671:2018+A2:2022
circuits following connection
of equipment
permits t h e test voltage applied t o
to b e reduced to 2 5 0 V DC, provided that
cables were tested at 5 0 0 V DC prior to connection.
G u i d a n c e Note 3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
67
2
643.3
BS 7 6 7 1 requires that insulation resistance is measured between all of the live
conductors and between the live conductors and the protective conductor, with the
protective conductor connected t o t h e earthing arrangement. During t h e test between
live conductors and the protective conductor, the live conductors may b e connected
together. Taking cables as an example, historically, it was acceptable to test a cable
between the various cores, and test to earth (which was actually only the cpc, such as
a single-core conductor, o r the armouring or sheath of the cable); sometimes, these
cables were terminated without further testing. This is n o longer acceptable: it is n o w
essential to test to t h e protective conductor (such as armouring) with this connected
- via a fly-lead if necessary - to the installation earthing arrangement.
This is shown
in Figure 2.23. It is a good idea to test all cables, including those tested during the
construction
stage, using this method.
The purpose of the insulation resistance test is t o verify that the insulation of conductors
is not damaged and that live conductors or protective conductors are not short-circuited.
As a reminder, prior to carrying out t h e test, t h e inspector should check that:
(a) t h e protective conductor of t h e i t e m (switchgear or cable, etc.) is connected to
t h e MET, which must b e connected to the means of earthing.
(b) pilot or indicator lamps, and capacitors, are disconnected f r o m circuits, to avoid
an inaccurate test value being obtained (see Note below).
(c) voltage-sensitive electronic equipment, such as dimmer switches, touch switches,
delay timers, power controllers, electronic starters for fluorescent lamps, emergency
lighting, RCDs and similar equipment is disconnected, so that it is not subjected
to the test voltage. The functional earthing leads of residual current circuit-breakers
(with overcurrent protection) (RCBOs) should also be disconnected, to prevent a
low insulation resistance reading or damage to an RCBO.
(d) the incoming neutral has been disconnected/isolated, where necessary, so that
there is n o connection to Earth.
Notes:
1
Great care should b e taken w h e n removing neutral conductors or neutral links
o n installations: the m o m e n t the neutral is removed, it may become live, if
there is a 'borrowed neutral' o n t h e installation. Insulated tools should b e used
for this task.
2
(b) and (c) are necessary because,
as testing occurs between
all conductors,
anything connected and in circuit will b e subjected to t h e test voltage.
Instrument: use an insulation resistance tester (see Section 4.4).
Table 64
Insulation resistance tests should be carried out using the appropriate DC test voltage
specified in Table 6 4 of BS 7671. The installation will b e d e e m e d to conform with
t h e Regulations in this respect if the main switchboard and each distribution circuit
tested separately, with all its final circuits connected b u t with current-using equipment
disconnected,
has an insulation resistance not less than that specified in Table 64,
reproduced here as Table 2.9.
68
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2
▼ T a b l e 2 . 9 M i n i m u m values of insulation resistance
Test voltage DC
(V)
Minimum
insulation resistance
(MQ)
SELVand PELV
250
0.5
Up to a n d including 500 V,with t h e exception
of SELVand PELV, but including FELV
500
1.0
Above 5 0 0 V
1000
1.0
Circuit nominal voltage
Simple installations that contain no distribution
circuits should preferably b e tested as
a whole (see example in Figure 2.21).
The tests should b e carried out with the main switch off, all fuses in place, switches
and circuit-breakers closed (i.e., in their O N positions), lamps removed, and fluorescent
and other discharge luminaires and other equipment disconnected. Where the removal
of lamps and/or the disconnection
of current-using equipment
is impracticable,
the
local switches controlling such lamps and/or equipment should b e open. An insulation
resistance test of line and neutral (L&N) connected together to Earth (E) will ensure
that all t h e circuit conductors are tested. Where there are special lighting controls,
such as contactor switching, all the circuit wiring, including such switch-lines, must b e
included in the testing.
Complex installations, or other installations where the overall installation presents a l o w
value, may n e e d to b e subdivided into their component
resistance tests.
parts to perform insulation
Although an insulation resistance value as low as 1 M Q would comply with the
requirements
of the Regulations, a new installation should not yield a test result this
low. In n e w installations, a value below 20 M Q should b e investigated.
Example (i): insulation resistance test of a whole consumer unit
▼ Figure
2.21 Example of a n insulation resistance test of a whole consumer
unit
□
Test w i t h 2-way switches in
all combinations.
Main switch off, secured by safety
locking device.
All fuses inserted, circuit breakers on.
Loadsdisconnected.
General lighting service (GLS)lamps
removed. Switches "on".
>5 5 Emo
Means o f earthing and
main bonding connected.
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
69
2
Figure 2.21 shows an example of testing a whole consumer unit (i.e., an installation)
in one test (only the L-N test is shown). The tests required are a test between the
live conductors (L-N) and tests between t h e live conductors and earth (L-Eand N-E).
For circuits containing two-way switches or two-way and intermediate
switches, the
switches must b e operated one at a time and the circuits subjected to additional
insulation resistance test in these configurations.
For circuits and/or equipment that is vulnerable t o the test voltage, the line and neutral
conductors can b e linked/connected together and a test made between t h e linked
conductors and protective Earth (as in L&N-E). It is essential that the incoming earth
connection is connected to the MET of the installation (and that this is connected to
t h e means of earthing) for these tests.
Example (ii): insulation resistance test of a final circuit
Figure 2.22 shows a n example of testing a single final circuit at a consumer unit (only
the L-N test is shown). The tests required are a test between the live conductors (L-N)
and tests between t h e live conductors and earth (L-Eand N-E).
For circuits containing two-way switches o r two-way and intermediate
switches, t h e
switches must be operated one at a t i m e and the circuits subjected to additional
insulation resistance test in these configurations.
For circuits and/or equipment vulnerable to the test voltage, the line and neutral
conductors can b e linked/connected together and a test made between t h e linked
conductors and protective Earth (as in L&N - E). It is essential that t h e incoming earth
connection
is connected to the MET of the installation (and that this is connected to
the means of earthing) for these tests.
▼ Figure 2 . 2 2 Example of insulation resistance test of a final circuit
?© =© -©
Test w i t h 2-way and
intermediate switches i n all
combinations.
SHI,
L
M a i n switch off, secured by safety
locking device.
All fuses inserted, circuit breakers on.
Loads disconnected.
General lighting service (GLS) lamps
removed. Switches "on".
>EIEIEImq
|0
Means of earthing and
main bonding connected.
Notes:
1
T h e test should b e initially carried o u t o n t h e complete installation, b u t could b e carried
out on completion of wiring at 500 V DC, before the installation of accessories, then retested
at 2 5 0 V DC on completion to verify cables have not been damaged during the work.
2
Bonding a n d earthing connections are i n place.
70
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2
Circuits with equipment that might influence the result of, or be damaged
during, an insulation resistance test
643.3.3
Some electronic equipment
may be susceptible to damage by insulation resistance
tests, for example where electronic components
that are not intended to withstand
voltages of 5 0 0 V DC.
Other equipment
may influence
equipment may have:
(a) electronic
the
measurement
being
made.
components o r transformers connected between
For example,
line and neutral,
which present a relatively low resistance;
(b) electronic control devices that use multipole
relays or contactors disconnecting
all live conductors (including neutral), which return to the o p e n state w h e n
power is removed, such as when the circuit is made dead prior to test; and/or
(c) certain protective
surge protection
devices, such as RCCBs, RCBOs and AFDDs, as well as
devices and similar electronic components
that present a low
resistance during an insulation resistance test.
Regulation 643.3.3 of BS7671 requires that circuits with this type of equipment
have
an insulation resistance test in two stages:
(i)
When the circuit cables are first installed, an insulation
carried out between
protective conductor,
line conductors,
with
and between
t h e protective
resistance test is
line conductors a n d the
conductor connected to
the
earthing arrangement. Individual sections of a circuit may b e joined via
temporary connectors
in place of vulnerable equipment,
to test multiple
cable segments together in this way.
(ii)
Following connection of equipment that might b e damaged by, o r influence,
the test, a test at 2 5 0 V D C is to b e applied between live conductors and
t h e protective conductor connected to t h e earthina arrangement.
insulation resistance shall have a value of at least 1 M Q .
The
Example of the test prior to connection for insulation resistance of a
three-phase 4-core power cable
The cable is tested as per Table 2.10.
▼ T a b l e 2 . 1 0 Insulation resistance test o n 4-core p o w e r cable
Test 1
L I to L2
Test 2
L I to L3
Test 3
L2 to L3
Test 4
L I + L 2 + L3 (connected
together) to N
Test5
LI+L2+L3+N
(connected together) to E
The lowest value of these tests is recorded as
'between live conductors'
The lowest value of these tests is recorded as
'between live conductors a n d earth1
Notes:
1
It is essential for test 5 that t h e protective conductor of t h e cable is connected to t h e
installation's earthing arrangement.
2
Tests 4 a n d 5 can b e done individually, for test 4, each of LI, L 2 and L3 first to N a n d
for test 4, each o f L I , L2, L3 a n d N to E.
Guidance N o t e 3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
71
2
For experienced inspectors and testers, Table 2.11 shows h o w it is possible to reduce
t h e number of steps for insulation resistance to four. However, should any test yield
a reading lower than that referred to in Table 2.9, it will b e necessary to follow the
sequence stated in Table 2.10 to identify which conductors are affected.
▼ Table 2.11 Four-step insulation resistance test o n 4-core p o w e r cable
Test 1
L I to L2
L I to L2
Test 2
LI+L2toL3
L I and L2 linked together to L3
Test 3
L I + L2 + L 3 t o N
All line conductors linked together to neutral
Test 4
L I + L2 + L3 + N to E
All live conductors linked together to Earth
▼ Figure 2.23 Insulation testing of a 4-core p o w e r cable prior to termination
(showing the
neutral to earth test)
SWA cable
Connection for
test purposes
AUTO M
Voitef
Phase
Connected
to MET
The insulation resistance readings obtained
should b e not less than the minimum
values referred to in Table 2.8.
Example of an insulation resistance test on a circuit with equipment that
might be damaged during test
643.3.3
Figure 2.24 illustrates the test carried out following connection of equipment that might
be susceptible to damage during a n insulation resistance test. Prior to connection of
the equipment,
all cables of the circuit should b e tested at 5 0 0 V DC, as described
previously. Following connection of the sensitive equipment,
provided that wiring has
been previously tested at 5 0 0 V DC:
(a) insulation resistance tests on a circuit are carried out at 2 5 0 V DC;
(b) the test voltage is recorded o n t h e schedule of test results; and
(c) the test is carried out between live conductors and cpc, with live conductors
connected together.
In simple installations, such as dwellings, in which m o s t circuits contain sensitive
equipment,
o r equipment
that might
affect the test, provided
all cables in the
installation have been tested in accordance with Table 6 4 of BS 7671 (Table 2.8) prior
to connection, this test could b e carried o u t for t h e whole installation.
72
G u i d a n c e Note 3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2
▼
Figure 2.24 Insulation resistance test of a complete circuit with sensitive equipment
following connection of cables
.* > * ♦ « * *> * * ♦ * *
lili
'O
SMART-touch LED dimmers
t h a t might be damaged during
insulation resistance test
Main switch off, secured by safety locking
device.
General lighting service (GLS) Lamps
Removed. Switches "on".
When originally installed, cables of circuit
tested prior to connection in accordance
with Table 64 of BS 7671.
643.3 2.6.8
Confirming
testing
a
>E3E3E3mq 2
Votts/
Means o f earthing and
main bonding connected.
SELVor PELV circuits by insulation
resistance
In order to establish which insulation resistance tests are required for verifying a SELV
or PELV system, t h e requirements of Section 414 of BS7671 must first b e understood.
There are situations where the provision of insulation of SELVor PELV circuits for basic
protection is generally not required by BS7671, i.e. forthe following voltages:
414.4.5 (a) up to 12 V AC or 3 0 V DC in wet areas; and
(b) up to 2 5 V AC or 60 V D C in dry areas.
Par
However, for locations containing a bath or shower, or i n swimming pools, saunas and
some other special locations, basic protection by insulation is required for SELVand
PELV at all voltages.
It is often, therefore, easier to carry out insulation resistance tests o n these circuits as
a matter of course.
Where SELVor PELV is used as a protective measure, a n d insulation resistance testing
is required, Tables 2.12 and 2.13 set out the requirements.
Instrument:
use an insulation resistance tester for these tests (see Section 4.4).
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
73
2
643.3.2
▼
T a b l e 2 . 1 2 SELVinsulation resistance tests
Test type
Description
Basic insulation
Between live conductors a n d all other
Test voltage
DC(V)
Minimum
acceptable
resistance
(MQ)
250
0.5
250
0.5
circuits, including other SELVand PELVand
l o w voltage (LV) circuits
Live to Earth
Note:
643.4.2
Between all SELV live parts a n d Earth
In situations w h e r e t h e SELV conductors are separated by insulation only covering
conductors of b o t h voltage bands, such as within a multicore cable with LV circuits,
t h e n t h e test voltage shall b e increased to 5 0 0 V D C a n d t h e insulation resistance
shall b e n o t less t h a n 1 M Q .
▼ Table 2.13 PELVinsulation resistance tests
Test type
Description
Basic insulation
Between live conductors a n d all other
circuits, including other SELVand PELVand
LV circuits
Note:
Test voltage
DC (V)
Minimum
acceptable
resistance
(MQ)
250
0.5
In situations w h e r e t h e PELV conductors are separated by insulation only covering
conductors o f b o t h voltage bands, such as within a multicore cable w i t h LV circuits,
t h e n t h e test voltage shall b e increased t o 5 0 0 V DC a n d t h e insulation resistance
shall b e n o t less t h a n 1 M Q .
643.4.3
2.6.9
Testing of electrically
separated circuits
The source of supply should b e inspected to confirm compliance with the Regulations.
In addition, should any doubt exist, the voltage should b e measured to verify that it
does not exceed 5 0 0 V.
Insulation tests are then made as detailed in Table 2.14.
Instrument:
use an insulation resistance tester for these tests (see Section 4.4).
▼ Table 2 . 1 4 Tests m a d e t o verify electrical separation
74
G u i d a n c e Note
Test voltage
DC(V)
Minimum
acceptable
resistance
(MQ)
Between t h e electrically separated live
conductors a n d t h e transformer
secondary live conductors
500
1.0
Basic insulation of the
separated conductors
Between t h e electrically separated live
conductors a n d their corresponding
exposed-conductive-parts
500
1.0
Basic insulation of any
exposed- conductiveparts associated with
separated conductors
Between any exposed-conductive-parts
associated with t h e electrically
separated circuits and any protective
conductor, other exposed-conductiveparts or Earth
500
1.0
Test type
Description
Basic separation
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Additional inspections and tests for separated circuit supplying m o r e than
one item of current-using equipment:
418.3.4
(a ) Apply a continuity test between all exposed-conductive-parts
of the separated
circuit to ensure that they are b o n d e d together. Carry o u t a 5 0 0 V DC insulation
resistance test between the non-earthed protective bonding conductor and:
(i)
the protective conductors and/or exposed-conductive-parts of other circuits;and
(ii) extraneous-conductive-parts.
The insulation resistance should b e not less than 1.0 M Q . Instruments:
low-resistance ohmmeter
use a
and an insulation resistance tester for these tests. See
Section 4.
(b) All socket-outlets m u s t b e inspected t o ensure that the protective conductor
contact is connected to t h e non-earthed protective bonding system.
(c) All flexible cables other than those supplying Class II equipment must b e
inspected to ensure that they contain a protective conductor for use as an
unearthed
418.3.7
protective bonding conductor.
(d ) Operation of the protective device must b e verified by measurement of the
fault loop impedances (i.e. between live conductors) to t h e various items of
connected equipment. These values should then b e compared with the
maximum
Z s value required by Regulation 411.4.5, with reference to the t y p e
and rating of the protective device for the separated circuit. For 2 3 0 V systems,
Tables 41.2 and 41.3 of Chapter 41 of BS 7671 may b e used for the maximum
Z s values for fuses and circuit-breakers, respectively. Although
these tables
pertain to t h e line/protective conductor loop path, and the measured values are
between live conductors, they give a reasonable approximation t o the values
required to achieve the required disconnection
2.6.10 Testing of functional
411J
extra-low
time of Table 41.1.
voltage (FELV) circuits
A FELV system is an extra-low voltage system meeting the requirements of Regulation
Group 411.7 (Functional extra-low voltage (FELV)). The system does not m e e t all the
requirements of Section 414 of BS 7671 relating to SELVor PELV.and its use is
permitted only where SELVor PELVare not necessary.
Regulation 643.3.2
requires that FELV circuits shall meet t h e test requirements
for
LV circuits (such as 'mains voltage' circuits). This includes t h e testing of:
$45
(a) continuity of protective conductors (see Section 2.6.5);
(b) insulation resistance (see Section 2.6.7); the test voltage being 5 0 0 V DC and
t h e minimum
643.6
insulation resistance being 1 M Q
and
c
( ) polarity (see Section 2.6.12).
It should also b e checked by inspection that:
41L7.2
(a )
the
exposed-conductive-parts
of t h e FELV system are connected
to the
protective conductor of the primary circuit of the source, provided that the
primary circuit is subject to protection by ADS in accordance with Regulations
b
the
411.3 to 6;
411.7 ( )
source of t h e FELV system is one that meets t h e requirements of
Regulation 411.7.4; and
(c) plugs,
socket-outlets,
connecting
luminaire
supporting
couplers
(LSCs), devices
for
luminaires (DCLs) and cable couplers in a FELV system are required
to have a protective conductor
contact (connected
to the protective
conductor)
and not b e dimensionally compatible with those used for any other systems in
use at the same premises.
Guidance Note 3: I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
75
2
134.5
A D S f o r protection
against electric
shock
is not r e q u i r e d i n a FELV system,
but may b e
r e q u i r e d f o r o t h e r r e a s o n s , s u c h a s p r o t e c t i o n against t h e r m a l e f f e c t s .
418.1.2 2.6.11 Proving and testing o f non-conducting
location
643.5
resistance/impedance o f floors and walls)
(insulation
I n t h e rare c i r c u m s t a n c e s w h e r e f a u l t p r o t e c t i o n i s p r o v i d e d by a n o n - c o n d u c t i n g
location
(which
should
be remembered
general application), the following
as a measure
of protection
not recognized
should be verified, prior to carrying out insulation testing:
( a ) e x p o s e d - c o n d u c t i v e - p a r t s should b e inspected
to c o n f i r m that under
c i r c u m s t a n c e s n o - o n e c a n c o m e into s i m u l t a n e o u s c o n t a c t w i t h :
(i)
(ii)
for
ordinary
two e x p o s e d - c o n d u c t i v e - p a r t s ; o r
a n exposed-conductive-part a n d a n y extraneous-conductive-part
if t h e s e p a r t s are liable to b e at different potentials t h r o u g h failure of t h e basic
insulation
(b)
of a live p a r t ;
i n a non-conducting location, t h e r e m u s t b e n o protective conductors; a n d
(c)
a n y socket-outlets
i n s t a l l e d in the
l o c a t i o n m u s t not
incorporate a n earthing
contact.
Note:
In B S 7671:2018+A2:2022, Appendix 1 3 provides guidance on escape routes a n d
fire protection. There is n o longer guidance in BS7671 for measurement of insulation
resistance/impedance of floors a n d walls to earth o r the protective conductor system.
Following t h e s e checks, t h e insulation resistance b e t w e e n t h e insulating floors a n d
643.3
w a l l s to t h e installation
MET
(via a l o c a l e a r t h terminal
of the
general
installation)
s h o u l d b e m e a s u r e d . It i s r e q u i r e d t h a t a t l e a s t t h r e e m e a s u r e m e n t s a r e made.
One
m e a s u r e m e n t m u s t b e m a d e a p p r o x i m a t e l y 1 m f r o m a n y accessible e x t r a n e o u s conductive-part,
f o r e x a m p l e , metal
pipe,
i n the
l o c a t i o n . The other
measurements
s h o u l d b e m a d e a t d i s t a n c e s f u r t h e r a w a y . M e t h o d s of m e a s u r i n g t h e i n s u l a t i o n
resistance/impedance
of f l o o r s a n d w a l l s a r e d e s c r i b e d below.
Testmethod
The insulation
resistance
S e c t i o n 4.4).
T h e t e s t is m a d e b e t w e e n t e s t e l e c t r o d e 1 o r t e s t e l e c t r o d e 2 ( s e e
Figures 2 . 2 5 a n d 2.26)
test may b e m a d e u s i n g a n i n s u l a t i o n resistance
a n d the m a i n protective
conductor
tester (see
of t h e installation.
Measuring insulation resistance of floors and walls
A
magneto-ohmmeter
o r battery-powered
insulation
a n o - l o a d v o l t a g e o f a p p r o x i m a t e l y 5 0 0 V (or
i n s t a l l a t i o n exceeds
The
r e s i s t a n c e tester
providing
1 , 0 0 0 V if t h e rated voltage of t h e
5 0 0 V) is u s e d a s a D C source.
r e s i s t a n c e is m e a s u r e d between
t h e test
electrode a n d t h e m a i n protective
c o n d u c t o r of t h e installation.
The test e l e c t r o d e s may b e either
of the f o l l o w i n g types.
o f t e s t e l e c t r o d e 1 i s t h e reference
method.
It i s r e c o m m e n d e d t h a t t h e test i s m a d e b e f o r e
(varnishes, p a i n t s a n d similar p r o d u c t s ) .
76
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
I n c a s e of dispute,
the application
the use
of the s u r f a c e treatment
2
Test electrode 1
The test electrode shown in Figure 2.25 comprises a metallic tripod, of which the
parts resting o n the floor f o r m the points of a n equilateral triangle. Each supporting
part is provided with a flexible base, ensuring, w h e n loaded, close contact with the
surface being tested over an area of approximately 9 0 0 m m 2 and having a combined
resistance of less than 5,000 Q between the terminal and the conductive rubber pads.
Before measurements
are made, the surface being tested is cleaned with a cleaning
liquid. While measurements
of t h e floors and walls are being made, a force of
approximately 7 5 0 N (75 kg in weight) for floors or 2 5 0 N for walls is applied t o the
tripod.
▼ Figure 2 . 2 5 Test electrode 1
039
021
10
180
15
5 mm — ♦
aluminium plate
view from above
23
033
profile view
section of a contact stud in
a conductive rubber
Dimensions in millimetres
terminal
contact stud in
conductive rubber
view from below
Test electrode 2
The test electrode shown in Figure 2.26 comprises a square metallic plate with sides
that measure 2 5 0 m m and a square of dampened, water-absorbent paper, o r cloth,
f r o m which surplus water has been removed, with sides that measure approximately
270 mm. The paper or cloth, as applicable, is placed between the metal plate and the
surface being tested. During measurement,
a force of approximately 7 5 0 N (75 k g in
weight) for floors or 2 5 0 N for walls is applied to the plate.
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
77
2
▼ Figure 2.26 Test electrode 2
750 N
wooden plate
L
metal plate
damp cloth
floor covering
subfloor
PE
Expected results
The floors and walls are considered to b e non-conducting where t h e measured
resistances are at least 5 0 kQ (where the system voltage to Earth does n o t
exceed 500 V).
645.5
A further test is specified in BS 7671 for extraneous-conductive-parts
that are within
the location, b u t to which insulation has been applied during construction. I n these
cases, a 'flash' insulation tester is required, which, after t h e standard 5 0 0 V insulation
test, applies a 2 kV AC root mean square (rms) test and measures the leakage current
(which should not exceed 1 mA).
643.6 2.6.12 Polarity
testing
The polarity of all circuits must b e verified before connection t o the supply, with either
an ohmmeter or the continuity range of an insulation and continuity tester. A typical
test o n a lighting circuit is shown in Figure 2.27.
Alternatively, polarity can b e verified by visually checking core colours at terminations,
thus verifying t h e installer's connections. Whatever m e t h o d is used, polarity checks are
required at all points o n a circuit to ensure that conductors have not been crossed at
intermediate
connection
points such as junction boxes.
Instrument', use a low-resistance ohmmeter for these tests (see Section 4.3).
A test for polarity is necessary to ensure that all fuses and single-pole control and
protective devices are connected in t h e line conductor. The centre contact of
screw-type lampholders must b e connected to the line conductor (except EI4 and E27
t o BS EN 60238), so this needs to be verified, as does the correct connection
non-reversible
plugs and socket-outlets. It is important
of all
to remove all other lamps o n
t h e circuit, as these may provide a conductive path between
line and neutral which
would t h e n permit an incorrectly connected lampholder to indicate continuity.
Note:
78
The continuity test (see Section 2.6.5) and ring final circuit continuity test
(see Section 2.6.6) help to confirm polarity.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
2
F i g u r e 2 . 2 7 P o l a r i t y test o n a l i g h t i n g c i r c u i t
S
//
I ‘i
/
/
/
/
I
T/
[O]
Temporary shorting link
.
/
Polarity test is carried out at single
pole switching devices, and screw
type lampholders (except E14and E27
t o BSEN60328).
AUTO |
REMEMBER TO REMOVE THE TEMPORARY SHORTING LINK WHEN TESTING
IS COMPLETE.
2.6.13 Earth electrode
resistance
testing
T h r e e m e t h o d s of measuring t h e resistance of a n earth electrode are described i n this
s e c t i o n . Test m e t h o d E l u s e s a d e d i c a t e d e a r t h e l e c t r o d e t e s t e r (fall o f p o t e n t i a l ,
t h r e e - o r f o u r - t e r m i n a l type);
(stakeless o r p r o b e type);
test m e t h o d E2 uses a dedicated earth electrode tester
a n d test m e t h o d E 3 u s e s a n EFLI tester.
Test m e t h o d E l : measurement using a dedicated earth electrode tester
(fall of potential, three- or four-terminal type)
For safety
reasons, it i s essential
t h e supply.
Caution: If this i s the only e a r t h electrode,
electrode/MET.
installation
t o ensure that the i n s t a l l a t i o n i s securely
isolated f r o m
It i s a l s o n e c e s s a r y to d i s c o n n e c t t h e e a r t h i n g c o n d u c t o r f r o m the e a r t h
unprotected
this m a y leave the
against e a r t h faults, so complete
isolation of the
installation
must b e m a d e . This d i s c o n n e c t i o n w i l l e n s u r e t h a t t h e test c u r r e n t
p a s s e s only
through
installation
t h e e a r t h e l e c t r o d e a n d not
m u s t remain
isolated
and t h e e a r t h e l e c t r o d e connection
Ideally, the test should
f r o m the supply
t h r o u g h any parallel paths.
until all testing
The
completed
reinstated.
be carried out when the ground conditions are least favourable, such
as when the soil i s frozen or very dry. Refer to Annex C of I E C 60364-6
The t e s t requires
h a s been
t h e use of two t e m p o r a r y test spikes (electrodes),
for further guidance.
a n d is c a r r i e d o u t
i n t h e f o l l o w i n g manner.
Guidance
© T h e Institution
Note
3: I n s p e c t i o n & Testing
of Engineering
a n d Technology
79
2
C o n n e c t i o n to t h e earth e l e c t r o d e is made using terminals
C l a n d P I of a four-terminal
e a r t h tester. To e x c l u d e the r e s i s t a n c e of t h e test l e a d s f r o m t h e resistance
reading,
individual leads s h o u l d b e t a k e n f r o m t h e s e terminals a n d c o n n e c t e d separately to
t h e electrode.
be linked
Where
together
t h e test lead
resistance
at the test instrument
i s insignificant,
a n d connection
t h e two terminals
m a d e with a single
may
test lead,
w i t h t h e s a m e b e i n g t r u e if u s i n g a t h r e e - t e r m i n a l tester. C o n n e c t i o n t o t h e t e m p o r a r y
spikes is m a d e as s h o w n i n F i g u r e 2.28.
▼
2 . 2 8 Typical earth electrode test using a three- o r four-terminal
Figure
tester
Temporary test
VoKW
Pha»e
\
Test spike
(current,
note 3)
' ' Test spike
(voltage,
note 2)
Electrode
under test
(note 1 )
3 m
3m
15 - 2 5 m
15 - 2 5 m
Notes:
1
2
3
4
Connect to terminals Cl and P I of four-terminal tester, or terminal X of a three-terminal tester.
Connect to terminal P2 of a four-terminal tester, o r terminal P of a three-terminal tester.
Connect to terminal C 2 of a four-terminal tester, or C of a three-terminal tester.
Voltage test spike is moved in t h e directions shown.
The d i s t a n c e b e t w e e n t h e test spikes is i m p o r t a n t . If t h e y a r e t o o c l o s e together,
their
r e s i s t a n c e areas w i l l o v e r l a p . I n general, r e l i a b l e r e s u l t s m a y b e e x p e c t e d i f t h e d i s t a n c e
between
t h e e l e c t r o d e under
maximum
dimension
test a n d the current
of t h e e l e c t r o d e system,
spike, C2, i s at least ten times
f o r example,
the
3 0 m for a 3 m long r o d
electrode.
Three readings
(a)
a r e taken:
firstly, w i t h t h e p o t e n t i a l spike,
under
test a n d t h e current
with
T 2 moved
T2, inserted m i d w a y b e t w e e n t h e electrode
spike, T l ;
(b)
secondly,
to a position
1 0 7o of t h e o v e r a l l electrode-to-current
(c)
last, w i t h T 2 m o v e d t o a p o s i t i o n 1 0 7o o f t h e overall d i s t a n c e t o w a r d s t h e
s p i k e d i s t a n c e b a c k t o w a r d s t h e e l e c t r o d e u n d e r test; a n d
c u r r e n t spike, f r o m its initial position
between
t h e e l e c t r o d e u n d e r test a n d T I .
By c o m p a r i n g t h e t h r e e r e a d i n g s , a p e r c e n t a g e d e v i a t i o n c a n b e d e t e r m i n e d . T h i s i s
calculated by taking the average of the three readings, finding the maximum
deviation of
the readings from this average in ohms, and expressing this a s a percentage of the average.
80
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2
The accuracy of t h e measurement using this technique is typically 1.2 times t h e
percentage deviation of t h e readings. It is difficultto achieve an accuracy of measurement
better than 2 °/o,and inadvisable to accept readings that differ by m o r e than 5 7o. In
this event, to improve the accuracy of the measurement,
t h e test must b e repeated
with a larger separation between the electrode under test and the current spike.
The test instrument output may b e AC o r reversed DC to overcome electrolytic effects.
Because these instruments employ phase-sensitive detectors, the errors associated
with stray currents are eliminated.
The instrument should b e capable of checking that the resistance of the temporary
spikes used fortesting iswithinthe accuracy limits stated in t h e instrument specification.
This may b e achieved by an indicator provided on the instrument,
or t h e instrument
should have a sufficiently high upper range to enable a discrete test to b e performed
o n the spikes.
Where the resistance of the temporary spikes is t o o high, measures to reduce the
resistance will b e necessary, such as driving the spikes deeper into the ground or
watering with brine t o improve t h e contact resistance. Umno c i r c u m s t a n c e s should
the latter technique b e used to temporarily
e a r t h electrode under test.
ON COMPLETION
IS
reduce the resistance
OF THE TEST, ENSURE THAT THE EARTHING
RECONNECTED,
BEFORE
THE
INSTALLATION
IS
of t h e
CONDUCTOR
ENERGIZED
(OR
RE-ENERGIZED).
Test method E2: Measurement using a dedicated stakeless or clamp
based earth electrode tester
643.7.2
A number of types of earth electrode resistance tester are available that utilize clamps
542.1
and can carry o u t measurements without the earth electrode under test having t o b e
disconnected
from the installation. The use of two such types is described here.
I n s t r u m e n t using o n e test c o i l
The instrument described here uses a m e t h o d of measurement similar to the fall o f
potential m e t h o d (test method E l , described earlier), in that it uses two temporary test
spikes (electrodes), as shown in Figure 2.29. These are placed in the ground, away
f r o m t h e earth electrode under test, in similar fashion to that described for t h e fall in
potential method.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineeringand Technology
81
2
▼ Figure 2.29 Instrument using one test coil
To main earthing terminal
of installation
Current clamp
containing test coil
AUTO fi
|o
vottu
Phase
Electrode
under test
(voltage)
15 - 2 5 m
Temporary test
Test spike
(current)
| ,
15 - 2 5 m
The clamp containing the test coil is placed around the earth electrode
o r around the conductor
under test,
connected to that electrode. This eliminates the effects of
parallel resistances, so that only the resistance earth electrode under test is measured.
The resulting level of accuracy is similar to that given by the fall of potential method.
Instrument
using two test coils
The instrument
described here relies for its operation o n there effectively being a
number of earth electrodes within t h e installation, and not just the electrode under
test. The electrodes other than the one under test might not b e actual earth electrodes;
they might b e extraneous-conductive-parts
buried in the ground o r in concrete buried
in the ground, such as metallic services pipes or buried structural metalwork or, in TN
systems, the means of earthing of the supply if this is connected during t h e test.
The instrument uses two coils placed a small distance apart around the earthing
conductor of t h e installation, as shown i n Figure 2.30, by means of clamps forming
part of t h e instrument. In practice, t h e coils may b e combined into a single clamp. O n e
coil induces a known voltage in a loop circuit containing t h e earth electrode under test,
the general mass of Earth and other connections with earth within the installation. The
second coil measures the test current.
82
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineeringand Technology
2
▼ Figure 2.30 Instrument using two test coils
Installation main
earthing terminal
@ @ @ ® ® ®
;
'
@® ® ® ® ® ® ®
Constant
voltage
10
\
Induced
current
measurement
,clamp
Electrode under
test (having
resistance to
Earth RE )
The instrument
carries out a calculation using the formula below. This produces a
resistance reading intended to represent the resistance of the earth electrode under test.
Rreading =
+ J.+ _L+ _L+>>-+ J.
Rj
Rj
Rn
where:
reading is the
resistance reading given by the test instrument
Re is the actual resistance of the earth electrode under test
Rb R 2 etc. are the resistances of the other 'earth electrodes'
The accuracy of the test reading ( R rea ding) depends on t h e existence of multiple parallel
paths for t h e returning test current to t h e instrument,
such that t h e effective parallel
resistance of these paths is low enough to b e neglected.
For example, if there were four other 'earth electrodes', effectively connected i n parallel,
each having a resistance of, say, 4 0 Q, their combined resistance would b e 10 Q . If the
resistance of the earth electrode under test was 100 Q, the total resistance, Rrea ding.
measured by t h e test instrument would be 100 Q +10 Q=110 Q . Consequently, the
measured value ( Rrea ding) would b e 1 1 o 7o of the actual value (RE), an error of 10 °/o.
However, if there was only one earth electrode other than the o n e under test, the error
in the measurement could b e significantly greater, as t h e effective path would t h e n b e
through t w o electrodes effectively connected in series. Using the same values as in
the previous example, this would m e a n that the resistance, Rrea din g , measured by the
test instrument would be 100 Q + 4 0 Q =140 Q . Consequently, Rrea ding would then
b e 140 7 o o f the actual value (R E), an error of + 4 0 7o.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
83
2
Usually, a n e a r t h e l e c t r o d e test
is c a r r i e d o u t to e n s u r e t h a t the
r e s i s t a n c e R e i s less t h a n a s p e c i f i e d v a l u e . Since
Reading > R e , using
earth electrode
method
E 2 may
b e m o r e appropriate i n installations w h e r e t h e c o m b i n e d resistance of o t h e r e a r t h
e l e c t r o d e s , o r the e f f e c t i v e e a r t h e l e c t r o d e f o r m e d by e x t r a n e o u s - c o n d u c t i v e - p a r t s ,
a n d the electrode
under
test, i s l e s s t h a n the limit
i s u s e f u l a t p r o p e r t i e s w h e r e g r o u n d is not
r e q u i r e d f o r R e . The test method
available t o i n s e r t m e a s u r e m e n t e a r t h
electrodes T 1 a n d T2 for test m e t h o d E l , for example, d u e to extensive p a v e d o r
t a r m a c s u r f a c e s , a n d the use of test method
E3 is not d e s i r a b l e due to safety concerns.
Testmethod E3: Measurement using an earth fault loop impedance (EFLI)tester
An e a r t h e l e c t r o d e may b e tested
using a n EFLI tester. However,
the results m a y not b e a s accurate
a s using a dedicated
it is recognized
that
e a r t h e l e c t r o d e tester.
F O R SAFETY REASONS, T H E INSTALLATION M U S T B E ISOLATED FROM T H E SUPPLY
B E F O R E DISCONNECTING
T H E EARTHING CONDUCTOR.
T h e EFLItester i s c o n n e c t e d
b e t w e e n the line c o n d u c t o r a t t h e source of the installation
a n d the e a r t h e l e c t r o d e via
t h e e a r t h i n g c o n d u c t o r , a n d a test p e r f o r m e d . T h e i m p e d a n c e r e a d i n g t a k e n i s t r e a t e d
a s t h e electrode
resistance.
ON COMPLETION OF THE TEST, ENSURE THAT THE EARTHING CONDUCTOR
IS RECONNECTED BEFORE THE SUPPLY IS ENERGIZED (OR RE-ENERGIZED).
Results of earth electrode testing
For TN-S systems
s u p p l i e d by
t r a n s f o r m e r o r generator
a d i s t r i b u t i o n n e t w o r k operator,
o r a distribution
having its own earth e l e c t r o d e a c c o r d i n g to BS7430, electrode
r e s i s t a n c e v a l u e s m a y n o t h a v e b e e n s p e c i f i e d , a s t h e r e is a s e p a r a t e m e t a l l i c e a r t h
conductor a n d electrodes often simply provide a local reference earth.
For installations
that
c o n t a i n generators,
including
static
c o n v e r t e r s (inverters)
o p e r a t e i n d e p e n d e n t l y , o r a s a s w i t c h e d a l t e r n a t i v e to t h e p u b l i c supply,
e l e c t r o d e s h o u l d c o m p l y w i t h the r e c o m m e n d a t i o n s of B S 7430,
Practice
for Electrical
Energy
Storage
Systems
that
t h e earth
o r the IET Code
of
a s appropriate.
For T T s y s t e m s , i n t h e a b s e n c e o f t h e d e s i g n e r ' s s p e c i f i c a t i o n , B S 7 6 7 1 m a x i m u m
values where
Regulation
4T1.5.3
R C D s a r e used for automatic
disconnection
of supply
that
by
are addressed i n
411.5.3.
R e g u l a t i o n 411.5.3 requires:
(a) t h e
disconnection
time
shall
R e g u l a t i o n 4 1 1 . 3 . 2 . 3 o r 411.3.2.4;
be
required
Regulation
411.3.2.2,
and
(b) R a x lAn < 50 V
where:
Ra
is the sum of the resistances of the e a r t h electrode a n d the protective
c o n d u c t o r ( s ) c o n n e c t i n g it to the e x p o s e d - c o n d u c t i v e - p a r t s ( i n Q ) .
iAn
is t h e rated r e s i d u a l o p e r a t i n g current
For a nominal
voltage,
of the R C D (in a m p s ) .
U o , of 2 3 0 V , Table 2.15
gives m a x i m u m values
n o n - d e l a y e d RCDs, w h i c h m a y b e s u b s t i t u t e d f o r R A i n e q u a t i o n (b) a b o v e .
84
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© The Institution
of Engineering and Technology
of Z s f o r
2
▼ Table 2.1 5 Maximum values of EFLI (Z s) for non-delayed RCDs to BS EN 61 008-1 and
BS EN 61009-1 for U o of 2 3 0 V
Maximum value of EFLI, Zs (Q)
RCD rated residual operating
current, l/\n (mA)
Where a time-delayed RCD is used t o provide fault protection, t h e maximum value
of EFLI, including t h e earth electrode resistance, must b e such that the requirements
of 411.3 and 411.5 are met. This is likely to require a lower figure than given above.
The table indicates that the use of a suitably rated RCD will theoretically allow m u c h
higher values of R A, and therefore of Z s, than could b e expected by using the circuit
overcurrent devices for fault protection.
Note:
643.7
It is advised, however, in Note 2 of Table 41.5, that earth electrode resistance values
above 2 0 0 Q may not b e stable, as soil conditions change due to factors such as soil
drying and freezing.
2.6.14 Protection by automatic disconnection of supply (ADS)
The effectiveness of measures for fault protection by ADS can b e verified for installations
within a TN system by:
(a) measurement of EFLI (as described in 2.6.15);
(b) confirmation by
short-time
visual inspection
that
overcurrent
devices
have
suitable
or instantaneous tripping setting for circuit-breakers, or current rating
(l n) and t y p e for fuses; and
(c) where RCDs are employed
to meet disconnection times for ADS, testing to
confirm that the disconnection times of Chapter 41 of BS 7671 can b e m e t by
verifying EFLI, and testing operation of RCDs (see Sections 2.6.15 and 2.6.18).
For installations within a TT system, effectiveness can be verified by:
(a) measurement
of
the
resistance
of
the
exposed-conductive-parts of the equipment
(b) confirmation
short-time
by
visual
inspection
that
earthing
arrangement
of
the
for the circuit in question;
overcurrent
devices
have
suitable
or instantaneous tripping setting for circuit-breakers, or current rating
(l n) and type for fuses; and
(c) where RCDs are employed, testing to confirm that the disconnection times of
Chapter 41 of BS 7671 can b e met by verifying EFLI, and testing operation of
RCDs (see Sections 2.6.15 and 2.6.18).
643.
643.7.3
Where RCDs are required for additional protection,
operation of RCDs (see Section 2.6.18).
this is verified by testing the
2.6.15 Earth fault loop impedance (EFLI) verification
Where limitation of EFLIis part of a protective measure, it is fundamental that t h e initial
verification process includes verification of EFLIs.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
85
2
The earth fault current loop comprises the following elements, starting at the point of
fault o n t h e L-Efault loop:
(a) the cpc;
(b) the MET and earthing conductor;
(c) for TN systems, t h e metallic return path or, in t h e case of TT and IT systems,
t h e earth return path;
(d) t h e path through the earthed neutral point of the transformer;
(e) the transformer winding (or the equivalent in another source of energy); and
(f) the line conductor f r o m the ’source’ to t h e point of fault.
There are two methods used for verifying total EFLIfor a circuit:
1
measurement
of total EFLI(Zs) using an EFLItester, where it is safe to d o so; or
2
measurement
of (R] + R 2) during continuity
testing of a circuit (see Sections
2.6.5 and 2.6.6) and addition to the measured EFLI external to that circuit (Z e).
The latter is preferred w h e n determining Z s for final circuits and distribution circuits.
Measurement
o f total E F L I ( Z
Measurement
using a n E F L I t e s t e r
of Z s is made o n a live installation and, for safety and practical reasons,
neither the connection with Earth nor bonding conductors are disconnected. Where
measurements are made close to a transformer, an instrument with suitable resolution
is required.
Instrument:
Note:
use an EFLItester for this test (see Section 4.5).
An EFLItester may not produce an accurate reading in installations with grid-connected
or island-mode (grid-forming) inverters (see Section 2.6.24).
M e a s u r e m e n t o f (R! + R2) d u r i n g continuity
t o t h e EFLI e x t e r n a l t o t h a t c i r c u i t (Z e)
testing of a c i r c u i t a n d addition
This procedure is described in Section 2.6.5 and, for ring circuits, Section 2.6.6. The
(Ri -I- R 2) value recorded for a particular circuit is added to the EFLI at the origin of
that circuit.
F o r a consumer unit at t h e origin of an installation, this is as follows:
Zs = Ze + (Ri + R2)
where:
Zs
Ze
(R 1 + R2 )
is the total EFLI in Q
is the external EFLI'external' to the installation
is the measured resistance of t h e line conductor and cpc, measured
during the continuity test method 1 or step 3 of the ring circuit
continuity test.
For consumer units or distribution boards not at the origin, confusion can arise over the
term 'external EFLI'(Z e) and some prefer to write or note t h e EFLI at the distribution
board as Zdb- As this value is not external to the installation, the formula is modified to:
Zs = Zdb + (Ri + R2)
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2
Circuit-breakers a n d residual current devices (RCDs)
The test (measuring)
current of EFLI testers may trip some types of 6 A Type B
circuit-breakers and any RCD protecting t h e circuit. This will prevent a measurement
being taken and may result in a n unwanted disconnection of supply to the circuit
under test.
Instrument
manufacturers
can supply l o o p testers that are less liable to trip RCDs by
either limiting t h e test current (to less than 15 mA) or by DC biasing (this technique
saturates the core of the RCD prior to applying the test).
M e a s u r e m e n t o f external EFLI (Z e)
542 4 2
The
externa
l EFLI, Z e , is measured using an EFLItester at the origin of the installation.
The impedance measurement is made between t h e line conductor of the supply and
the means of earthing with
t h e main
switch open
or with
all t h e circuits
isolated. The means of earthing must b e disconnected f r o m t h e installation MET for
t h e duration of t h e test, to remove parallel paths. Care should b e taken to avoid any
shock hazard to the testing personnel and other persons on the site, both whilst
establishing contact and whilst performing t h e test. It is strongly recommended to
check
for diverted neutral
currents
where there is a TN-C or TN-C-S earthing
arrangement, or where PME conditions apply (see Appendix E).
ENSURE THAT THE EARTH CONNECTION
THE INSTALLATION
H A S BEEN RECONNECTED BEFORE
IS ENERGIZED (OR RE-ENERGIZED).
See Figure 2.31 for test method connections.
Instrument:
use a n EFLItester for this test (see Section 4.5).
▼ Figure 2 .31 Example of a test for Ze at the origin of a small installation
| pate I
I
[oonia i&h i<wh|
0101
■O
gBfflBBfla
Main switch off,
secured by safety
locking device.
Test between i n c o m i n g l i n e
conductor a n d t h e m e a n s o f
earthing,
which s h o u l d be
disconnected from t h e rest
100 A
of t h e installation, a n d f r o m
extraneous-conductiveparts, s o t h e r e a r e n o
parallel p a t h s .
As previously mentioned, the measured Ze can be used to add to circuit (Rj + R2) values.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineering and Technology
87
2
Determining
external EFLI(Ze) by enquiry
The external EFLI,Ze, can b e determined
by enquiry with the electricity
distributor.
However, if this is relied upon, a test must b e made to verify that t h e D N O earthing is
effective. A test lamp may b e used to check that current is able t o pass between line
and the means of earthing. Alternatively, an EFLItester can b e used to verify that the
value of Ze is consistent with that quoted by the distributor o r measured previously.
Verification of EFLItest results
643 J
K i s important to recognize that BS 7671 requires the inspector not only to test the
installation, but also to compare the results with relevant design criteria (or with criteria
within BS7671). This may seem obvious, b u t it is not u n c o m m o n for some inspectors
to pass test information back to their office without making the necessary comparisons,
possibly assuming that t h e office or someone else will check t h e results. The office
might then assume that t h e inspector has checked t h e results against criteria, whereas
in fact, no-one
has. It is important to remember
that the person w h o signed the
certificate is responsible. Employees should follow their employer's
respect of methods for determination of prospective fault current.
procedures
in
Values of Zs should b e compared with o n e of the following:
(a) for standard thermoplastic (polyvinylchloride Appendix A of this Guidance Note.
Table 4 1 2
Table 4L4
(b ) EFLI figures provided
PVC) circuits, the values i n
by the designer. See also Appendix
A, which provides
information o n how to correct measured results for ambient temperature, as
this m a y not have been done by the designer (the inspector will need to clarify
this point).
(c) tabulated values in BS 7671, corrected for temperature. See Appendix A, which
provides information o n how to correct measured results for ambient temperature.
(d) using a factor of 0.8 (see Appendix A2).
Appendix A provides a formula for making temperature
adjustments,
together with a
worked example.
643.7.3.201
2.6.16 Prospective fault current (l pf )
Regulation 643.7.3.201
introduces the requirements of Regulation 434.1 into t h e
testing section, with the designer required to determine t h e prospective fault current
under both short-circuit and earth fault conditions a t every relevant point o f t h e
installation.
This may b e done by calculation, b e ascertained by enquiry or b e
measured
directly using an instrument
(inspection).
The expression 'every relevant
point’ means every point where a protective device is required to operate under fault
conditions,
and includes the origin of the installation. Appendix 14 provides s o m e
further guidance on these requirements.
The inspector must have knowledge of the design in this respect as, for example, if t h e
switchgear at the origin of a n installation is suitably rated for prospective fault current,
a n d switchgear of similar short-circuit rating is used downstream
of that point, then
n o further checks will b e necessary. This is because the magnitude of the prospective
fault current decreases with increasing distance downstream
of the origin, assuming
there is not another source of supply, such as a generator, connected to t h e installation
at a point other than the main supply terminals of the installation. Any fault current
contribution f r o m a generator must b e included if the generator can operate in parallel
with the supply. If a generator or other source can supply the installation in place of
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t h e normal supply, then generally fault currents will b e significantly lower and t h e
protection may take longer to clear a fault, making it possible that t h e l 2 t contribution
could cause thermal damage t o some cables or equipment.
Regulation 434.5.1 requires that, except where back-up protection is provided by
another device in accordance with the second paragraph of that regulation, the breaking
capacity rating of each protective device shall be not less than the prospective fault
current at its point of installation. The t e r m 'prospective
fault current' includes t h e
prospective short-circuit current and the prospective earth fault current. The maximum
prospective fault current at the point of installation of a protective device is the greater
of these t w o prospective fault currents at that point, which should b e determined and
compared with the breaking capacity of the device.
W i t h t h e p o w e r on, the m a x i m u m v a l u e of t h e prospective short-circuit current
can b e obtained by direct connection of t h e instrument between live conductors at
the protective device at t h e origin or other relevant location within t h e installation. Both
two-lead and three-lead instruments capable of determining prospective fault current
are available; it is important that any instrument
used is set to the correct range and
connected i n accordance with the manufacturer’s instructions for its use. Failure to do
so could b e dangerous, could result in damage to t h e instrument and might result in
misleading readings being obtained.
Instrument:
use the prospective fault current range of a suitable EFLItester for this test
(see Section 4.5, final paragraph).
With some instruments,
the voltage between
line conductors
cannot b e measured
directly. Where this is t h e case, it can b e assumed that for three-phase supplies,
the maximum
balanced prospective short-circuit level will be, as a rule of thumb,
approximately twice the single-phase value. This figure errs o n the side of safety.
Where a n instrument is rated for the higher voltage, a more accurate prospective fault
current measurement, for a three-phase installation, can b e obtained by measuring the
line-to-line fault current and dividing the measured result by 0.87.
Prospective earth fault current may b e obtained with the same instrument. Again, care
must b e taken to ensure that t h e instrument is set correctly and connected as per the
manufacturer's instructions for use.
Appendix 14 of BS 7671 provides a reminder
measurements
of the hazards involved
directly from live parts. Guidance in HSE publication
in taking
HSR25 should
b e followed.
It is recommended
t h a t alternative m e a n s a r e u s e d t o d e t e r m i n e prospective
fault current w h e r e possible.
Where a measurement of prospective fault current is necessary, it should always b e
made downstream of a protective device rated for t h e anticipated prospective fault
current. Fused test leads alone are not considered suitable for this purpose, and, in t h e
absence of a suitable protective device, a temporary one should b e fitted.
Note:
A prospective fault current tester may not produce an accurate reading in installations
with grid-connected or island-mode (grid-forming) inverters (see Section 2.6.24).
Guidance N o t e 3: Inspection & Testing
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89
2
The values obtained should b e compared with t h e breaking capacity of t h e appropriate
protective device. The breaking capacity of t h e protective device should b e greater
than the highest value of prospective fault current obtained using the instrument.
Whichever is the greater of the prospective
short-circuit
current and the prospective
earth fault current obtained should be recorded o n the EIC,EICRand the Schedule of
Test Results, as appropriate.
If t h e measured value of prospective fault current appears to exceed t h e fault current
rating for t h e equipment
the current-limiting
or protective device, further consideration m u s t b e given to
effect of any upstream protective devices and the ability for the
source of supply to deliver the indicated prospective fault current. The maximum value
of prospective fault current for an installation will be with t h e installation unloaded and
t h e conductors at ambient temperature.
F o r a three-phase system, the prospective three-phase short-circuit current will always
b e larger than the single-phase line-to-neutral
or earth fault currents.
Note on the accuracy of EFLIand prospective fault current testers (see also
Sections 2.6.24 and 4.5)
EFLI testers become less accurate at low value impedance readings, such as w h e n
measuring
close to a transformer
noted that the standard instrument
or other low impedance
used for determining
source. It should b e
prospective fault current is
effectively an EFLI instrument.
While earth fault loop testers should have a resolution of at least 0.01 Q, this should
not b e confused with accuracy.
A displayed test result of less than about 0.1 Q, or about 1.0 Q,when o n the lower
current range (such as 15 mA), could b e prone to significant errors. Such errors can
significantly affect the calculation o f prospective fault current.
Should more accurate measurements b e needed o n large installations with very low
impedance supplies, specialist high-current four-wire EFLI testers are available.
Note:
An EFLI and prospective
in
installations
(Section
with
current
tester
grid-connected
fault
or
may not produce
island-mode
a n accurate reading
(grid -forming)
inverters
2.6.24).
Rated short-circuit breaking capacities of protective devices
The rated short-circuit
capacities of fuses, circuit-breakers to BS EN 6 0 8 9 8 and
B S 3 8 7 1 (now withdrawn) and RCBOsto B S E N 61009 are shown in Table 2.16. Note
that B S 3 8 7 1 identified the short-circuit capacity of circuit-breakers with an 'M1 rating.
90
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▼ T a b l e 2 . 1 6 Rated short-circuit capacities of protective devices
Device type
Semi-enclosed fuse to BS 3 0 3 6 with category
of duty
Device
designation
Rated short-circuit
capacity (kA)
S1A
1
S2A
2
S4A
4
General-purpose fuse to BS 88-2
System E (bolted) type
80 kA at 400 V
System G (clip in) type
50 kA at 230 V o r
8 0 kA a t 400 V
Domestic fuse to BS 88-3 ____________________________________________________
Circuit-breakers to
■cn
les
1.5
(1-5)
3.0
(3-0)
6
(6-0)
10
(7-5)
15
(7.5)
20
(10.0)
25
(12.5)
1
B S E N 6 0 8 9 8 and RCBOsto B S E N 61009*
BS 1361 fuses (BS 1361 has been withdrawn, but these
fuses will still be found in existing installations)
Domestic fuse to BS 1361
Circuit-breakers
to BS 3871 (replaced by BS EN 60898)
Two short-circuit capacity ratings are defined in BS EN 6 0 8 9 8 and BS EN 61009:
l c n : the rated short-circuit capacity (marked o n t h e device); and
l c s : the service short-circuit capacity.
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
91
2
The difference between the two short-circuit ratings described above is the condition
of the circuit-breaker after manufacturer's
testing.
I c n is the maximum fault current that the device can interrupt safely, although its
characteristics may have been altered and i t may n o longer b e usable.
Ics is the maximum
loss of performance.
fault current that the
The l c n value (for example, 6,000)
device can interrupt safely without
is marked o n the device in a rectangle. For
t h e majority of applications, t h e prospective
fault current at t h e terminals of t h e
circuit-breaker should not exceed this value.
For domestic installations, t h e prospective fault current is unlikely to exceed 6 kA, up to
which value l c n will equal l cs - (For domestic installations, the D N O may specify a higher
fault current value - perhaps up t o 16 kA - but this level is rapidly reduced through
the impedance
of t h e supply cables.)
For switchgear, the relevant fault current (short-circuit)
rating of t h e switchgear
(or assembly) should b e equal t o or exceed the maximum prospective fault current
at the point of connection to the system. For non-domestic installations o n the public
supply network, this information will have to b e obtained f r o m t h e local DNO.
The terminology
to define the short-circuit
rating of an assembly is given in the
BS EN 61439 series of standards as follows:
(a) rated short-time withstand current l cw ;
(b) rated peak withstand current Ipij and
(c) rated conditional short-circuit current l cc .
Further details are provided in Guidance Note 2.
Fault currents up to 16 kA
Except in London and some other major city centres, the maximum
fault current for
2 3 0 V single-phase supplies up to 1 0 0 A is unlikely to exceed 16 kA. Appendix 14 of
BS7671 advises that it is often not necessary to measure o r calculate the prospective
fault current at the origin of individual dwellings or similar premises i n which the
distributor has declared the prospective fault current to b e 16 kA:
In dwellings (household) or similar premises, where a consumer unit to BS EN 61439-3
is used and the maximum
prospective
fault current declared by the distributor
is
16 kA, it is n o t necessary t o measure or calculate prospective fault current at the origin
of the supply.
The term 'distribution board for operation by ordinary persons' used in BS EN 61439-3
applies to a wider range of products
than a domestic
consumer
unit. The 16 kA
conditional rating applies only to consumer units as defined in B S 7 6 7 1 as follows:
Consumer unit (may also b e k n o w n as a consumer control unit or electricity control
unit). A particular type of distribution board intended for operation by ordinary persons,
comprising
a type-tested
co-ordinated
assembly for t h e control and distribution
of
electrical energy, incorporating manual means of double-pole isolation on the incoming
circuits) and an assembly of one or more protective devices, signalling and other
devices proven during the type-test of t h e assembly as suitable for such use.
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536.4.201 The short-circuit capacity of OCPDs individually having a short-circuit capacity rated less
than 16 kA, but incorporated within consumer units, may b e taken to b e 16 kA where:
(a) the installation has a supply provided
in accordance with the ESQCR, with a
nominal voltage of up to 2 5 0 V A C ;
(b) the service cutout is a fuse rated 100 A or less complying with either BS 1361
(Type II) o r BS 88-3;
(c) t h e consumer unit complies with either:
(i) BS EN 61439-3 (including t h e 16 kA conditional short-circuit
test described
in Annex ZB of t h e standard), incorporating only components and protective
devices specified by t h e manufacturer; or
(ii)
(for initial verification of additions a n d alterations to existing installations
with older consumer units) either:
•
BS 5486-13:1979
with label 'CM16';
•
BS 5486-13:1989;
or
•
BS EN 60439-3
(including
the
16 kA conditional
short-circuit
test
described in Annex ZA of the standard), incorporating
only components
and protective
(see Regulations
devices specified
by the manufacturer
432.1 and 530.3.4 of BS 7671:2008).
Recording the prospective fault current
Both t h e E l C a n d the EICR contain a section headed 'Nature of Supply Parameters',
which requires the prospective fault current at the origin to b e recorded. The value to
b e recorded is the greater of either the short-circuit current (between
o r the earth fault current (between
line conductors)
live conductors)
and the MET). If it is considered
necessary to record values at other relevant points, this can b e done o n the Schedule
of Test Results. Where the protective devices used at t h e origin have the necessary
rated breaking capacity, a n d devices with similar breaking capacity are used throughout
t h e installation, it can b e assumed that the Regulations are satisfied in this respect
for all distribution boards (provided there is n o t another source of supply, such as a
generator, connected to the installation at a point other than the main supply terminals
of t h e installation)(see also Section 2.6.24).
2.6.17
643.9
Phase sequence
testing
Regulation 643.9 requires verification that the phase sequence is maintained for
multiphase circuits within an installation. In practice, this will b e achieved by checking
polarity a n d connections throughout the installation. While the regulation requires phase
sequence to b e maintained throughout the installation, this should not b e confused
with phase rotation. Phase rotation is a description of which way a correctly-wired
three-phase induction motor will run. If t h e timing of t h e sine waves o n LI, L 2 and L3
are such that LI precedes L2, which precedes L3, then t h e motor will run clockwise.
If t h e timing of t h e sine waves is changed by swapping any two wires, as shown in
Figure 2.32, then the motor will run anticlockwise. To ensure correct operation
of
three-phase loads, for example three-phase laundry equipment, it is recommended
test phase rotation at t h e point closest to the load, before the load is energized.
to
Phase sequence
continuity
may b e confirmed,
with the installation/circuits
isolated, using
testing as for continuity of conductors. This may b e carried out using the
same method as Rj + R2 testing.
Guidance
© T h e Institution
Note
3: Inspection
& Testing
of Engineering a n d Technology
93
2
▼ Figure 2.32 All possibilities of swapping any two wires
Original 1-2-3
phase rotation
(wires 1 and 2 swapped)
phase rotation = 2-1-3
End result
2
1
3 ----------------------------------------------------- 3
(wires 2 and 3 swapped)
phase rotation = 1-3-2
1 ----------------------------------------------------- 1
2
3
2
(wires 1 and 3 swapped)
phase rotation = 3-2-1
3
2
2
3
Optionally,
a n d o c c a s i o n a l l y , t h e i n s p e c t o r may
a p h a s e rotation
tester,
w i s h to c h e c k p h a s e s e q u e n c e b y u s i n g
of e i t h e r :
(a)
a rotating
(b)
a n indicator l a m p type.
disc t y p e ; o r
I n s t r u m e n t s c o n t a i n i n g b o t h of t h e a b o v e f o r m s o f i n d i c a t i o n a r e a l s o a v a i l a b l e .
V a r i o u s types
of i n d i c a t i o n exist,
display
equivalent
(LCD)
leads
are connected
to
i n c l u d i n g a rotating
a n d other
the
disc,
m e a n s of indication.
i n s t a l l a t i o n and,
a n e l e c t r o n i c liquid
Generally,
crystal
coloured o r labelled
if t h e p h a s e sequence/rotation
i s correct,
t h e i n d i c a t i o n c o n f i r m s this.
In the c a s e of a rotating d i s c type instrument,
S o m e approved
offer
d o not
Both
over
standard three-wire
a t t a c h t h e wires
indicator l a m p type,
(formerly
types
d i r e c t i o n of
of
phase
rotation
R/B/Y)
t h e m . These
testers,
as they
t h e i n s t a l l a t i o n , n e e d i n g o n l y two
either the
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
L1/L2/L3
(formerly
R/Y/B)
lamp or the
l a m p will be illuminated.
sequence
i n d i c a t o r c a n a l s o b e u s e d to
a t t h e s u p p l y t e r m i n a l s to
l a b e l l i n g / i d e n t i f i c a t i o n of p l a i n c o n d u c t o r s .
94
to
p h a s e rotation
be probed with the hand-held probes.
the
L1/L3/L2
o r anticlockwise.
t e s t e r s h a v e a p h a s e r o t a t i o n f a c i l i t y b u i l t i n to
i n safety
r e q u i r e t h e i n s p e c t o r to
p h a s e s to
With
voltage
a n increase
the d i s c will rotate either clockwise
motors
verify p h a s e s e q u e n c e /
a n d to
confirm
the
correct
2
▼ Figure 2.33 Examples of phase sequence indication from phase rotation instruments
Indication type
Indication for
clockwise phase
rotation sequence
Indication for
anticlockwise p h a s e
rotation sequence
Alphanumeric
For example multifunction
tester, phase sequence
meter
Graphical symbols
For example multifunction
tester, phase sequence
meter
Illuminated L E D
For example approved
two-pole voltage tester
2.6.18 Operation
and functional
testing
of RCDs
The operating times of RCDs are required to b e tested i n t h e following circumstances:
643.7.1 (a) where they are relied o n for disconnection for compliance with Chapter 41 of
BS7671; and
643.8 (b) where they are installed as additional protection,
BS 7671.
as specified in Chapter 41 of
Where RCDs are installed with circuit-breakers and the circuit has the characteristics to
satisfy Chapter 41 of BS 7671 without the RCD,then testing of the RCDisnot essential
unless it is specified for additional protection.
Operation of R C D s
411.4.5 Before using a test instrument, the RCDtest button should b e pressed. This provides
4H.5.3 basic information that the RCD is functioning, and will help avoid danger that may
occur during test if the RCD did not respond.
BS EN 61557-6
requires the test current for a tripping test to b e applied at the
zero-crossing point of the AC wave. Therefore, for each of the tests, readings should b e
taken with the test waveform starting on both positive and negative half-cycles usually
identified '0°' and '180°’ o n test instruments, and the longer operating t i m e recorded
for t h e l x l An Type AC test.
Prior to these R C D tests, it i s essential,
for safety reasons, that the EFLI i s
tested to check the r e q u i r e m e n t s h a v e been met.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
95
2
Instrument: u s e a n RCD tester f o r t h e s e tests, (see Section 4.7). W h e r e t h e RCD
tester is capable of testing RCDs w i t h different residual current operating characteristics
(Type AC, Type A, Type F o r Type B), it s h o u l d b e configured f o r t h e correct setting f o r
t h e test b e i n g u n d e r t a k e n as indicated i n Table 2.17. RCDs are m a r k e d w i t h s y m b o l s t o
indicate their residual current operating characteristic as s h o w n i n Figure 2 . 3 4 .
▼ Table 2.17 Tests for RCDs
a Recommended
RCD
Types
tests
Instrument
RCD Type
setting
(note 1)
Applied
residual
current
Maximum expected tripping time (ms)
RCDs to harmonized
standards (note 2)
RCDs to BS 4293 or
BS 7288:1990 (note 3)
Non-delay
Non-delay
S-delay
Time-delay
All
Type AC
toxlAn
RCD should not trip
RCD should not trip
All
Type AC
IxlAn
(note 4)
300
200
500
{(0.5 to 1.0)
x time
deiay}+200
b Examples of optional RCD tests for fault-finding and similar purposes (see notes 5 and 6)
RCD Type
All RCDs with
residual current
rating 3 0 mA
or less
Instrument
RCD Type
setting
(note 1)
Applied residual
current
Type AC
Type AC
All RCDs with
residual current
rating exceeding
3 0 mA
Type A, F o r
B RCDs to a
harmonized
standard
(note 2)
Type A
(carry out
Type AC
tests first)
Type B RCDs to
a harmonized
standard
(note 2)
Type B
(carry out
Type AC and
Type A tests
first)
Maximum expected tripping
time (ms)
Non-delay
S-delay or
time-delay
5 x I a h o r 2 5 0 mA
(note 7)
40
150
5xlAn
40
150
V2x( /2xlAn)
pulsed DC
RCD should not trip
l x 0 / 2 x l A n ) pulsed DC
300
500
5 x ( 2 x lz\ n ) pulsed DC
40
150
2 x l / \ n smooth DC
300
500
Notes:
1 Where applicable, Instruments without an 'RCD Type' setting can only b e used to carry
out Type AC tests.
2
Harmonized standards for the purposes of Table 2.17a are considered to be
BS EN 61008, BS EN 61009, BS EN 60947-2 and BS 7288:2016. (BS 7288:2016 is the
UK implementation of HD 6 2 6 4 0 Residual current devices with or without overcurrent
protection for socket-outlets for household and similar uses').
3
RCDs to BS 4293 and editions of BS 7 2 8 8 earlier than BS 7288:2016 should b e tested
as Type AC only. Tests for other Types are not applicable for RCDs to these standards.
96
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
2
4
This test is required by Regulation 643.7 of BS 7671 (where the RCD is used for
automatic disconnection of supply) or Regulation 643.8 of BS 7671 (where the RCD
is used for additional protection). RCD to BS 4293 or BS 7288:1990 should meet the
operating times of the appropriate product standard, where these are shorter than those
specified in BS 7671 :201 8+A2:2022, because a longer operating time than that in the
relevant product standard may indicate that the RCD is n o longer operating correctly.
The longest tripping time for each of the two tests (0° and 180°) is recorded in
column 2 8 of the Schedule of Test Results (see example in Figure 5.6).
5
Optional tests are intended for fault-finding and similar purposes only. The performance
requirements of the optional tests are to be met by product manufacturers and are not
BS 7671 requirements. Not all test instruments can perform all of the tests listed here
(see note 1).
6
Since RCDs are only rated for a finite number of operations, carrying out frequent
optional tests can shorten the product's life. For example, in carrying out all of the
above tests, including optional tests, for a 30 mA Type B RCD, would require the RCD to
7
trip 12 times.
For RCDs to harmonized standards (see note 2), with residual operating current l An
30 mA,
the manufacturer may select a current for the Type AC 40 m s tripping test of 2 5 0 mA
instead of 5 x l An . Where this is declared by t h e manufacturer, failing to trip within 4 0 m s
at 5 x l An . does not necessarily mean the RCD is faulty. For this reason, and to prevent
shortening the usable life of RCDs (see note 5), BS 7671:2018+A2:2022
does not
require testing of RCDs at 5 x l An .
V
Figure 2 . 3 4 Markings o n RCDs for residual current operating characteristic
RCD Type
isymbol
symbol reference
in IEC 60417
T y p e A C to B S EN 61008,
or
6148
T y p e A to B S E N 61008,
B S E N 61009, B S E N 60947-2 or
6149
B S EN 61009, B S EN 60947-2
B S 7288:2016
B S 7288:2016
6149+6160
T y p e F to BS E N 62423
OR
or B S E N 60947-2
6399
— — — 6149+6160+6297
T y p e B to B S EN 62423 or B S
6398
EN 60947-2
OR
6150
S t y p e (time d e l a y ) in addition
6395
to one of the a b o v e markings
Note:
RCDs to BS 4293, and BS 7288:1 990, have no marking for residual current operating
characteristic. They would be considered equivalent to Type AC RCDs if assessing their
continued use with respect to additions to an existing installation downstream of the
device. The designer should also consider that there have been other improvements
in product standards for RCDs in relation to device characteristics, isolation,
short-circuit rating, reliability, and electromagnetic compatibility.
Guidance N o t e 3 : Inspection & Testing
© T h e Institution of Engineering and Technology
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2
RCD test method 1: residual current test applied between line and
protective conductor
RCDtest method 1 is preferred where RCDs are used for fault protection, as it provides
further validation that the RCD is operating within a specific t i m e for a simulated fault
to t h e relevant protective conductor.
The test is m a d e o n the load side of the RCD between
t h e line conductor
of t h e
protected circuit and the associated cpc. The load should b e disconnected during
the test to avoid spurious results. These tests can result in a potentially dangerous
voltage o n exposed-conductive-parts and extraneous-conductive-parts when t h e EFLI
approaches t h e maximum acceptable limits. Precautions m u s t therefore b e taken to
prevent contact of persons o r livestock with such parts.
It may not b e possible to use this test method
conclusively in s o m e situations, for
example where:
(a) there is an upstream RCD for which there is n o selectivity, such as a test on an
RCD in a caravan supplied f r o m a caravan site or repair workshop socket-outlet,
where B S 7 6 7 1 requires that the socket-outlet and caravan both have additional
protection by an RCD rated 3 0 m A or less. In these cases, either RCD may trip
first, and it is n o t guaranteed that t h e disconnection t i m e measurement will b e
that of t h e RCD under test.
(b) protective
conductor
currents
f r o m equipment
that cannot
b e disconnected
f r o m the circuit under test, or f r o m other parts of the installation
energized, affect the conditions
time measurement
that are
of the applied test so that the disconnection
is affected.
(c) an RCD in an IT system is being tested, and there is n o current return path via
a cpc.
RCDtest method 2: upstream/downstream test
Where RCDtest m e t h o d 1 cannot b e used conclusively, or it is not considered practicable
or safe to conduct a n EFLI test prior to testing the RCD, RCD test m e t h o d 2 can b e
considered. This method is outlined in Clause 6.3 of PD IEC/TR 6 2 3 5 0 Guidance for
the correct use of residual current-operated
protective devices (RCDs) for household
and similar use, which states that the test method
resistance or disconnected
avoids risks associated with high
protective conductors, a n d avoids instrument errors due to
protective conductor currents.
The test is m a d e between a live conductor o n the supply side (upstream) of t h e RCD
and another live conductor o n the load side (downstream)
of the RCD, for example:
(a) single-phase RCDs, o r three-phase RCDs with a monitored neutral, between
upstream neutral and downstream
(b) three-phase
(i)
(ii)
(iii)
(iv)
(v)
(vi)
Note:
98
line; or
RCDs without neutral, between
upstream LI and downstream
L2;
upstream LI and downstream
L3;
upstream L 2 and downstream
LI;
either:
upstream L 2 and downstream L3;
upstream L3 and downstream L I ; or
upstream L3 and downstream L2.
The instrument, test leads, and probes, must be rated for the line-to-line voltage of
the three-phase system at appropriate overvoltage category (see Section 1.1).
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
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2
Examples of testing an RCCBand RCBOare shown in Figures 2.35 and 2.36 respectively.
These examples are included to illustrate the principles only. The person carrying out
the test should take all practicable steps to avoid the risk of contact with live parts,
such as the example shown in Figure 2.37. The test should only b e performed with
covers removed, in equipment where all line conductor terminals meet IP2X/IPXXB.
Before attempting this test method, check with the test equipment manufacturer's
instructions that the method is supported by the instrument. Some test instruments
require only two test leads to be connected during the test, but some require three
test leads.
▼
Figure 2 . 3 5 Example of upstream/downstream test o n a single-phase RCD
a.
2-lead test (where supported by test equipment)
Other circuits
switched off
where possible
Supply
©'I © ©
Test is made between
line conductor at the
load side of the RCD,
and the neutral
conductor at the
supply side.
Check with test instrument
manufacturer that the
instrument is suitable for the
upstream/downstream test.
b.
© © ©
ms
I&. 30mA
3-lead test
©©©©©©©
Other circuits
switched off
where possible
Supply
©’ E3
©I© ©I©
Test is made between
line conductor at the
load side of the RCD,
and the neutral
conductor at the
supply side.
Check with test instrument
manufacturer that the
instrument is suitable for the
upstream/downstream
test.
© ©
ms
EF
W! ■«
-
OFF
l&n 30mA
TEST
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
99
2
▼ Figure 2.36 Example of upstream/downstream test on an RCBO
a.
2-lead test (where supported
by test equipment)
I
Supply
1
Other circuits
switched off where
possible
oet
Test is made between line
conductor at the load side of
the RCBO, and the neutral
conductor at the supply side.
C. J ms
Check with test instrument
manufacturer that the
instrument is suitable for the
upstream/downstream test.
b.
30mA
3-lead test
I \l 1
II
Supply
1
Other circuits
switched off where
possible
©
EERIE \ \
Test is made between line
conductor at the load side of
the ROBO, and the neutral
conductor at the supply side.
Check with test instrument
manufacturer that the
instrument is suitable for the
upstream/downstream test.
LJms
Un 30mA
M
In some cases, it is possible to conduct the upstream/downstream test without
having to remove equipment covers, as an upstream neutral can b e connected via an
appropriate socket-outlet combination. Examples are shown in Figures 2.37 and 2.38,
which illustrate arrangements to test a 3 0 m A RCD within a caravan, w h e n the caravan
is supplied f r o m a 3 0 m A RCD-protected socket-outlet at t h e caravan site pitch, or in
a workshop environment.
100
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
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2
▼
Figure 2 . 3 7 Example of upstream/downstream test for an RCD or RCBO in a caravan
(2-lead test)
caravan
inlet
-pitch
outlet
caravan
connecting
lead
pgSBs
downstream line
connection from
socket-outlet in
caravan, via
shrouded test
Y-splitter
\
Upstream
neutral
connection
from trailing
socket-outlet,
via shrouded y
test plug /
wander-lead
Plug
BS EN 60309-2
plug to BS 13632 trailing socket
outlet converter
2Q3ms
30mA
Check with test instrument manufacturer that the
instrument is suitable for the upstream/downstream
test
Figure 2 . 3 8 Example of upstream/downstream test for an RCD or RCBO in a caravan
(3-lead test)
Y-splitter
pitch
outlet
caravan
inlet
caravan
connecting
lead
|?BBB|B|B!
downstream line
connection from
socket-outlet i n
caravan, via
shrouded test
wander-lead
plug
Upstream
neutral —
connection
from trailing
socket-outlet,
via shrouded
test plug /
BS EN 60309-2
plug to BS 13632 trailing socket
outlet converter
30.3 ms
30mA
Check with test instrument manufacturer that the
instrument is suitable for the upstream/downstream
test
Guidance N o t e 3: Inspection & Testing
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101
2
Results of RCD tests
643.7
The maximum disconnection t i m e for a residual test current of l An should not exceed
643.8
t h e relevant non-time- delayed values shown in Table 2.17.
The maximum
disconnection
t i m e for a residual test current of | An for the AC test is
recorded in the Schedule of Test Results.
Integral test device
643.10
An integral test device is incorporated i n each RCD. This device enables t h e functioning
of t h e mechanical parts of the RCD to b e verified by pressing t h e button marked T
or 'Test 1.
Operation of the integral test device does not provide a means of checking:
(a) the continuity of the earthing conductor o r the associated cpcs;
(b) any earth electrode or other means of earthing;
(c) any other part of the associated installation earthing; or
(d) the sensitivity of t h e device.
514.12.2
The RCDtest button will only operate the RCD if it is energized. B S 7 6 7 1 recommends
that the test button is pressed at least every 6 months.
2.6.19 Other functional
643.10
testing
Other equipment, including switchgear, controls and interlocks, should also b e
functionally tested - that is, operated to confirm that they work and are properly
installed, mounted a n d adjusted.
The settings o n all adjustable relays and controls, etc. should b e checked to see that
they align with the designer’s proposed requirements.
RCD test buttons should b e
operated t o see that the RCD trips.
AFDDs have b e e n introduced in t h e 18th Edition of the IET Wiring Regulations (532.6).
There are two general types: those with a test button and those with an automatic test
facility. Functional testing can only b e carried out by pressing the test button; there is
n o means of functionally testing the t y p e without a test button.
Circuit-breakers should n o t b e used as lighting switches o n a regular basis (as in some
warehouses), unless they are approved by t h e manufacturers for such use.
2.6.20 Verification
of voltage drop
Verification of voltage drop is not normally required during initial verification. It is usually
sufficient to check that voltage drop calculations have been undertaken and that the
design voltage drops are within the limits required in BS7671.
Where it may b e necessary to verify that voltage drop does not exceed t h e limits stated
Sect 525
In the relevant product standards of installed equipment, B S 7 6 7 1 provides guidance
to d o so. Where no such limits are stated, voltage drop should be such that it does not
impair t h e proper a n d safe functioning of installed equipment.
Voltage drop problems are quite rare, but the inspector should b e aware that long runs
of circuit conductors and/or high currents can sometimes cause voltage drop problems.
102
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2
Accurate measurement of voltage drop within an installation is not practical, as this
would m e a n measuring the instantaneous voltage at both the origin and at t h e point of
interest simultaneously, together with the instantaneous load current. An indication of
voltage drop can b e obtained to ensure that it is not excessive for t h e proper functioning
of the equipment by simple voltage measurement at the equipment terminals with t h e
installation fully loaded.
Voltage drop may b e determined by measurement of the combined live conductor
resistance and by calculation using this value and the full load current of t h e equipment,
with compensation
for conductor temperature
difference for measured and operating
conductor values. This will determine voltage drop within the circuit, which can then
b e used to verify compliance.
Table 4Ab
Appendix 4 of BS 7 6 7 1 gives maximum values of voltage drop for lighting and for
other uses, depending u p o n whether an installation is supplied directly from a public
LV distribution network o r f r o m a private LV supply. The voltage drop for general
purposes in Appendix 4 exceed the requirements of s o m e product standards. For
example, BSEN 61851-1:2011 for electric vehicle charging equipment requires charging
points t o operate within a utilization voltage range of Uo ± 10 7o, which therefore
requires a maximum
voltage drop of 4 7o in a consumer's
installation supplied in
accordance with t h e ESQCR.
It should b e remembered that voltage drop may exceed t h e values stated in Appendix 4
in situations such as motor starting periods and where equipment
has a high inrush
current, where such events remain within the limits specified in the relevant product
standard or reasonable recommendation by a manufacturer.
2.6.21
Verification
of protection o f low voltage (LV) installations
against temporary overvoltages due to faults in the high
voltage (HV) or LV system
Sect 442 The protection
referred to in this section of the Guidance Note is the subject of
Section 4 4 2 of BS7671. F o r m o r e information, see Guidance Note 1.
442.2.1 Temporary overvoltages due to a n HV system fault
442.2.2
Regulations 442.2.1 and 442.2.2 give t h e requirements concerning the magnitude
and duration of temporary overvoltages occurring due to a fault in t h e HV system
(typically, 11 kV) supplying t h e substation f r o m which t h e LV installation is supplied.
442.2.3
Regulation 442.2.3 points o u t that t h e requirements of Regulations 442.2.1 and
442.2.2 are deemed to be met if the LV installation is supplied f r o m a system for
distribution of electricity t o the public. This assumes that the public electricity supply
distribution network is appropriately designed and constructed, as is the case in Great
Britain. Where this is the case, there is n o need for the inspector to check compliance
with Regulations 442.2.1 and 442.2.2.
442.2.1 Where the LV installation is supplied from a privately owned substation, the design
442.2.2 responsibility for complying with Regulations 442.2.1 and 442.2.2 rests with the
designer(s) of t h e substation and the associated LV distribution network up to the
incoming terminals of the LV installation. The inspector will need to b e in possession
of sufficient information
provided by this party (or parties) about the intended means
of compliance, to enable him or her to verify, so far as is reasonably practicable, that these
means have been properly put into effect. Matters to b e checked by the inspector include:
Guidance N o t e 3 : I n s p e c t i o n & Testing
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103
2
(a) that the HV and LV earthing arrangements of the substation have b e e n correctly
installed and that their resistances to Earth meet the designer's requirements;
(b) that t h e HV earthing and LV arrangements are interconnected or, where appropriate,
separated, according to t h e designer's requirements;
(c) that any global earthing
system or additional
connections
with Earth in the
LV network that are relied o n for safety are in existence and properly installed,
and that the resistance of connections with
requirements; and
Earth meets the
designer's
(d) that t h e rated currents and settings of protective devices are as intended by
the designer.
Temporary overvoltages due t o an LV system fault
442.3
Regulations 442.3, 442.4 and 442.5 require consideration to b e given to t h e stress
voltages that would occur in an installation in t h e event of loss of the neutral conductor
In a TN or TT system, a n earth fault in an IT system with distributed neutral, or a
short-circuit between a line conductor and a neutral conductor.
In practice, there is usually little that an installation
d o to meet the requirements
designer and constructor
can
of these regulations beyond selecting and installing
equipment with appropriate insulation voltage ratings, such as 600/1,000
V cables for
an installation of nominal voltage of 2 3 0 / 4 0 0 V. The inspector should check that this
has been done.
2.6.22 Verification of protection against overvoltages
origin or due t o switching
Section
GN1
Table 4 4 :
of atmospheric
The protection referred to in this section of t h e Guidance Note is the subject of
Section 443 of BS 7671. Formore information, see Guidance Note 1.
Irrespective of whether the electrical designer has chosen to specify SPDs, t h e
inspector should check that all electrical equipment of the installation has been so
selected and installed that, according to its product standards, it provides at least the
applicable value of rated impulse voltage referred to in Table 443.2 of BS 7671. The
values of rated impulse withstand voltage in that table are given according to the
Category (I, II, III or IV) into which the equipment falls and to t h e nominal voltage of
the installation. Table 4 4 3 . 2 of BS 7671 gives examples of equipment falling into each
of the categories.
Section 534
Where protection against overvoltages by the use of SPDs has been specified by the
designer, the inspector should check that these have been selected and installed in
accordance with t h e designer's requirements or otherwise in accordance with
Section 5 3 4 of BS7671.
The inspector needs t o verify that SPDs have n o t become expired or defective by
ensuring that indicator lights are correctly illuminated or that the coloured flag or flags
o n the devices indicate that they are serviceable. Remote status indicating facilities
such as connection to an audible alarm may also have been provided and this should
also b e checked for correct operation.
104
G u i d a n c e Note
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© The Institution
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2
2.6.23 Verification of measures against electromagnetic
disturbances
Sect 444
GN1
I n s p e c t o r s should
f a m i l i a r i z e themselves
with the section
o n avoidance
a n d reduction
o f e l e c t r o m a g n e t i c d i s t u r b a n c e s i n B S 7 6 7 1 ( S e c t i o n 4 4 4 o f B S 7671).
For m o r e
i n f o r m a t i o n , s e e G u i d a n c e N o t e 1.
It s h o u l d b e noted
t h a t compliance
E l e c t r o m a g n e t i c Compatibility
with
E M C requirements
Regulations
2016
in B S 7671
is something
that
a n d in the
i s not
usually
v e r i f i e d by t a k i n g site m e a s u r e m e n t s . For m o s t installations, E M C i s d e m o n s t r a t e d by
a c o m b i n a t i o n o f t h e i n s t a l l a t i o n design a p p r o a c h ( i n c l u d i n g , w h e r e a p p l i c a b l e , d e t a i l s
of E M C mitigation
measures),
i n f o r m a t i o n that would
p r o d u c t conformity,
need
to b e retained
a n d good
i n s t a l l a t i o n p r a c t i c e s . The
f o r the 'design
f i l e ' (which
needs
to be
r e t a i n e d by t h e ' r e s p o n s i b l e p e r s o n ’ , w h i c h , u n d e r t h e 2 0 1 6 r e g u l a t i o n s i s t h e installer)
might
include:
(a) f o r a s m a l l o r s i m p l e i n s t a l l a t i o n consisting
the EMC Regulations
solely
of equipment
complying
with
2016:
(i)
product
manuals
and
(ii)
notes on what was done
installation
instructions,
with
evidence
of
the
regulatory (UKCA o r UKNI) marking of products; a n d
(b) f o r a large o r complex
where instructions
installation,
could
not be followed
(if relevant);
o r where
t h e above
d o e s not a p p l y :
(i)
m a n u f a c t u r e r / i m p o r t e r d e c l a r a t i o n s of
conformity,
o r statements
(ii)
cable and product manufacturer's installation instructions and specifications; and
(iii)
design
of
EMC
s t a n d a r d s c o m p l i a n c e , etc;
•
drawings
design
►
a n d r e p o r t s demonstrating:
conformity
to relevant
installation
standards,
which
might
include:
B S 7671;
►
B S E N 50310;
►
B S E N 50174
►
B S IEC 6 1 0 0 0 - 5 - 2 ; a n d
►
o t h e r s (for
series;
s y s t e m s such
a s emergency
lighting,
fire alarms a n d
s o o n t h a t m a y h a v e a d d i t i o n a l E M C r e q u i r e m e n t s a s p a r t of t h e i r
system standards);
•
•
evidence
that manufacturer
instructions
measures
w h e r e t h e y c o u l d not be;
have been
followed,
or mitigation
product selection relevant for the E M environment (see P D IEC/TR 61000-2►
for larger installations/multi-use
►
a s t a t e m e n t o f mitigations
outside
5):
premises, E M e n v i r o n m e n t zoning; a n d
a n d r e s i d u a l risk f o r e q u i p m e n t i n s t a l l e d
the target E M environment.
S e c t i o n 4 4 4 s p e c i f i e s a d d i t i o n a l m i t i g a t i n g m e t h o d s f o r E M C a p p l i e d t o t h e design
installation of cables and equipment.
Many of these mitigating methods concern
and
the routing
of cables and their distance from other cables, a s well as providing equipotential bonding.
Thus, v e r i f i c a t i o n of E M C a n d c o m p l i a n c e with S e c t i o n 4 4 4 is as follows:
(a) c h e c k i n g t h e E M C d e s i g n h a s b e e n f o l l o w e d w i t h r e s p e c t to c a b l e routing,
s e p a r a t i o n distances,
(b) inspection
of
cable
use of suitable
sheath
and
containment
screen
n e c e s s a r y , c o n t i n u i t y c h e c k i n g of t h e s e items;
a n d enclosures,
terminations
and,
etc.;
if
considered
and
(c) c a r r y i n g o u t c o n t i n u i t y c h e c k s o f a n y a d d i t i o n a l m i t i g a t i n g b o n d i n g n e t w o r k
p r o v i d e d (for e x a m p l e , a l o c a l m e s h network).
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BS IEC 61000-5-2 contains guidance o n good installation practices for inspection
items, to achieve EMC. BS EN 50310 contains requirements for electrical tests to b e
carried out for bonding networks in buildings containing ICT systems.
While there are n o specific requirements
in BS 7671 for either installers or inspectors
to carry out electric field or magnetic field strength measurements, designs for certain
installations may require such measurements to b e made, based o n assessments
carried out at t h e design stage.
chapter 82 2.6.24
Prosumer's
electrical
installations
(PEIs)
A PEI is one in which electrical energy is both produced and consumed. The simplest
t y p e of PEI is an installation with a solar PV system.
This section
outlines particular considerations
installation. Further information,
for initial testing with this t y p e of
including guidance on initial verification, can be found
in the IET Code of Practice for Electrical Energy Storage Systems and the IET Code of
Practice for Grid-Connected
Note:
Solar Photovoltaic Systems.
In PEIs, the term power conversion equipment (PCE) is used to describe both
inverters and AC-DC converters, as a single device, such as a combined inverter
charger for a battery storage system, may perform both functions.
M u l t i p l e s u p p l i e s a n d safe i s o l a t i o n
PEIsusually have m o r e than one source of supply. Isolation of the electrical installation
for safe working o n certain parts of the installation will involve m o r e than one point
of isolation.
These should b e appropriately labelled in accordance with Regulation 514.15.1.
It is essential to follow a rigorous approach to the identification of the correct points
of isolation for t h e part of the system that is being worked on, along with the use of
means of securing the points of isolation in t h e OFF position.
Supply characteristics
may change between
installation
operating
modes
PEIshave operating modes as shown in Table 2.18. When t h e installation is operating
in island mode, the supply characteristics are likely to b e different, as the installation is
supplied by local generation (in t h e f o r m of power converters such as inverters) rather
than the public distribution
network. As a consequence
of moving from connected
mode to island mode, for example:
(a) The earthing arrangement may change, for example f r o m TN-C-S to TN-S, or
f r o m TT to TN-S. A consumer's earth electrode may b e required.
(b) The prospective
fault current is likely to b e far less, and the effective
greater, than in connected
modes of operation.
EFLI
In smaller installations, there
may be insufficient
fault current to operate overcurrent protective
RCDs or protection
built into electronic converters must b e used for protection
devices, a n d
against electric shock. Manufacturer’s instructions should b e consulted to check
whether external protective devices are required.
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▼
Table 2. 18 Operating modes for PEIs
Mode
Definition in Part 2 of BS 7671
______ _ _
Connected mode
Operating mode which needs connection to the public network
(direct feeding mode and reverse feeding mode).
Direct feeding mode
Operating mode in which the public network supplies the (PEI)
(see note 1).
Reverse feeding mode
Operating mode in which the PEI supplies the public network
(see note 2).
Island mode
Operating mode in which the PEIis disconnected from the public
distribution network, but remains energized (see note 3).
Notes:
1 Local storage units can supply current-using equipment or be charged by local power
supplies and/or the public distribution network.
2 Local storage units can supply current-using equipment and/or the public distribution
network or be charged by local power supplies.
3 An island mode can be either the result of an automatic process or the result of a
deliberate action.
643,73.1 Note 1 EFLI a n d p r o s p e c t i v e f a u l t c u r r e n t m e a s u r e m e n t i n PEIs
826.7 Grid-connected inverters operating in parallel with the public supply track the rise
and fall of the supply voltage. Consequently,
measurement
when a prospective fault current o r EFLI
is taken in a PEI in connected modes of operation, the contribution
of
the inverter may b e masked by this behaviour.
In island mode, inverters can appear to b e a constant current source, up to t h e value
of their in-built current limit.
When a prospective fault current or EFLI measurement
is taken in a PEI in island mode,
especially using a 'no trip' or 'low current' setting usually used to avoid tripping RCDs,
the prospective fault current reading may b e much higher than t h e actual value, and
the EFLI lower.
The IET Code of Practice for Electrical Energy Storage Systems advises:
(a) external earth fault loop impedance and prospective fault current measurements
are carried out at the origin, with all PCE isolated.
(b) earth fault loop impedance
and prospective
fault current
measurements
for
the remainder of the installation are not taken unless all the inverters in the
system are isolated. In order to provide verification for automatic disconnection
of supply, t h e following tests can b e used:
(i)
for connected mode: the verification of
earth fault loop impedance
(Zdb and Z$) is based o n the external earth fault loop impedance, Ze, plus
measured (R1+R2) values. Prospective fault current should b e the measured
prospective fault current plus the sum of t h e current limit of all connected
m o d e inverters.
(ii)
for island mode:
(Zdb and Zs)
manufacturer's
if applicable, verification
of earth fault loop impedance
is determined using measured (R1+R2) values, plus the
information regarding the value of Z e to b e assumed for the
EESSor the relevant PCE within it. Prospective fault current should b e t h e
sum of the current limit of all connected-mode inverters.
Note:
The prospective fault current measurement at the origin is not necessary if it can be
determined by other means (see Section 2.6.16).
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2
Functional testing and system documentation
Functional testing of the relevant management
a n d control devices c a n b e complex.
Particularly f o r dwellings, the level of documentation
b e extensive, a n d it i s important
maintenance
of the installation in future.
Code of Practice for Electrical
for Grid-Connected
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Solar
a n d commissioning
to check that suitable information
Further information
Energy Storage
Photovoltaic Systems.
records will
is provided
for safe
c a n b e found in the IET
Systems a n d the IET Code of Practice
Periodic inspection
and testing
3.1
651.1
3
Purpose of periodic inspection and testing
The purpose of periodic inspection and testing is to provide an engineering view o n
whether or n o t an installation is in a satisfactory condition where it can continue to
b e used safely.
A detailed visual examination of the installation is required, together with
appropriate
tests. The tests are mainly to confirm that the disconnection times stated in Chapter 41
of BS 7 6 7 1 are met.
The periodic inspection and testing is carried out, so far as is reasonably practicable, for:
(a) the safety of persons and livestock against the effects of electric shock and bums;
(b) protection
against damage
to
property by fire
and heat arising f r o m a n
installation defect;
(c) confirmation that t h e installation is not damaged or deteriorated so as to impair
safety; and
(d) the identification
of installation defects and departures f r o m the requirements
of B S 7 6 7 1 that may give rise to danger.
For an installation under effective supervision in normal use, periodic inspection
and testing may b e replaced by a n adequate regime of continuous monitoring and
maintenance of the installation and all its constituent equipment by skilled persons
competent in such work. It is important in such a regime that maintenance records,
with references to inspection and testing, are recorded and stored. Such records should
b e available for scrutiny and n e e d not b e in the standard EICRformat.
3.2
Necessity for periodic inspection
and testing
Periodic inspection and testing is necessary because all electrical installations deteriorate,
due to a number of factors, such as damage, wear, tear, corrosion, excessive electrical
loading, ageing and environmental influences. Consequently:
(a) legislation requires that electrical installations are maintained
in a safe condition,
and this lends itself to periodic inspection and testing (see also Tables3.1 and 3.2);
(b) licensing authorities, public bodies, insurance companies, mortgage lenders and
others may require periodic inspection and testing of electrical installations, as
is, for example, the case for HMOs (see Tables 3.1 a n d 3.2); and
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3
(c) additionally, periodic inspection and testing should b e considered in t h e
following circumstances:
(i) to assess compliance
(ii)
with BS 7671;
o n a change of occupancy of the premises (especially
for rented domestic
accommodation);
(iii)
(iv)
(v)
(vi)
o n a change of use of t h e premises;
after additions or alterations to the original installation;
where there is a significant change (increase) in the electrical loading of t h e
installation; and
where there is reason to believe that damage may have been caused to
t h e installation, as might b e the case, for example, after flooding.
Reference to legislation and other documents
requirements
is made below. It is vital that these
are ascertained before undertaking periodic inspection a n d testing.
3.3
Electricity at Work Regulations (EAWR)
3.3.1
The need for appropriate
inspection
and testing
Regulation 4(2) of t h e EAWR requires that:
As may b e necessary to prevent danger, all systems shall b e maintained
prevent, so far as is reasonably practicable, such danger.
so as to
HSR25, which provides guidance o n these regulations, advises that this regulation
is concerned with t h e need for maintenance to ensure the safety of the system,
rather than with the activity of carrying out t h e maintenance in a safe manner, which
is required by Regulation 4(3). The obligation to maintain a system arises if danger
would otherwise result. There is n o specific requirement
to carry out a maintenance
activity as such; what is required is that the system is kept in a safe condition. The
frequency and nature of the maintenance
must be such as to prevent danger so far
as is reasonably practicable.
There have been many debates as to what 'reasonably practicable' means. In the
event of an accident, i t would b e for a court to decide the issues. In essence, however,
the reduction of risk to as low as is reasonably practicable means weighing that risk
against the sacrifice needed t o further reduce it. The decision should b e weighted in
favour of health and safety, because the presumption
implement
is that t h e duty holder should
t h e risk reduction measure. To avoid having to make this sacrifice, the duty
holder must b e able to show that it would b e grossly disproportionate
to the benefits
of risk reduction that would b e achieved. Thus the process is not one of balancing t h e
costs and benefits of measures, b u t rather, of adopting measures except where they
are ruled o u t because they involve grossly disproportionate sacrifices.
Ultimately, under t h e EAWRit is the duty holder who is responsible for t h e safety of an
electrical installation at work. This leads to the question as to w h o the duty holder is.
In Section 4 of the Health a n d Safety at Work etc. Act 1974 (HSWA), reference is m a d e
to a person "who has, t o any extent, control of premises". This may b e an identified
person with that specific responsibility
within an organization, such as a landlord, or
perhaps a manager or supervisor.
Regular inspection of equipment, including the electrical installation, is a n essential
part of any preventative
maintenance
programme.
This regular inspection may b e
carried out as necessary without dismantling (or with partial dismantling, as required)
a n d supplemented
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by appropriate testing.
3
T h e r e i s n o s p e c i f i c requirement
requires
dismantling,
of c a b l e s or components,
However,
while
should
a r e j u s t i f i e d . Dismantling,
t h a t it is impractical
b e b a l a n c e d against the p o s s i b l e consequences
w o u l d ensue f r o m inspection,
a m a t t e r of a little
inspection
3.3.2
to dismantle
a n item
risks c o u l d b e i n t r o d u c e d f r o m u n s a t i s f a c t o r y reassembly,
f a i l i n g to i n s p e c t i n s i d e switchgear
a floor, t h e decision
the risks a s s o c i a t e d w i t h
a n d particularly d i s c o n n e c t i o n
i n t r o d u c e s a risk of u n s a t i s f a c t o r y reassembly.
it is e a s y t o decide
or that
o n e v e r y i n s p e c t i o n . Where testing
the i n s p e c t o r s h o u l d c o n s i d e r whether
d i s m a n t l i n g a n d reassembling
equipment,
to test t h e installation
of not d o i n g so, f o r example,
f o r signs of overheating.
f o r instance,
Where
Where
in
irreparable d a m a g e
i n l i f t i n g f l o o r t i l e s to inspect
not to i n s p e c t w o u l d b e justified.
extra w o r k o r inconvenience,
of
this
c a b l e s under
the decision
is simply
f o r e x a m p l e , i n c a r r y i n g o u t a visual
of c a b l e s in a d o m e s t i c d w e l l i n g l o f t void, it c o u l d b e d i f f i c u l t to justify.
Safety in inspection and testing
Safety issues i n general are outlined
testing, the inspector
risk assessments,
i n S e c t i o n 1. When carryingout periodic inspection
is advised to include the following
a n d test a n d inspection
procedures
considerations
and
when developing
for a particular installation:
(a) safety information in existing information a n d p r e v i o u s records for the installation;
(b) a n y e x i s t i n g risk a s s e s s m e n t s o r s a f e t y f i l e s held by t h e p e r s o n ordering the
work
(for
(Design
example,
the
h e a l t h a n d safety
a n d Management)
Regulations
file
2015
r e q u i r e d by the
Construction
(CDM));
(c) information
f r o m p r e - i n s p e c t i o n surveys; a n d
(d) the age of the installation, a n d probable p e r i o d since the last inspection
a n d test.
I n s p e c t i o n a n d testing
and those
c a r r y i n g out
discover
should
u n e x p e c t e d i s s u e s t h a t require
the inspections
3.3.3
of e x i s t i n g i n s t a l l a t i o n s m a y involve
i n s p e c t i o n a n d testing
unknowns,
r e m a i n a l e r t t o the
f a c t that
they
may
d y n a m i c risk a s s e s s m e n t s to b e c o n d u c t e d a s
a n d tests progress.
Diverted neutral currents
Installations
i n w h i c h P M E conditions
by o p e n - c i r c u i t protective
a p p l y c a n c a r r y diverted
e a r t h a n d neutral
neutral
(PEN) c o n d u c t o r faults.
currents
caused
Diverted neutral
c u r r e n t s m a y also b e e x p e r i e n c e d i n i n s t a l l a t i o n s w h i c h s h a r e e x t r a n e o u s - c o n d u c t i v e p a r t s , such
as c o n d u c t i v e gas or w a t e r s e r v i c e pipes,
i n s t a l l a t i o n s in w h i c h P M E conditions
o r s t r u c t u r a l steelwork,
with
apply. As a safety p r e c a u t i o n f o r t h o s e c a r r y i n g out
inspection
a n d testing, these types of installations
a n d testing
commences,
to determine
should
to i f diverted
neutral
b e checked
currents
before
inspection
a r e present.
A p p e n d i x E d e s c r i b e s a s a f e t y check p r o c e d u r e to i d e n t i f y d i v e r t e d n e u t r a l currents.
3.4
341.1
Design
W h e n c a r r y i n g o u t the design
of a n installation,
a n d p a r t i c u l a r l y when
e q u i p m e n t , the designer
s h o u l d t a k e into account
b e r e a s o n a b l y expected,
i n c l u d i n g t h e f r e q u e n c y of routine
between
subsequent
inspections
(supplemented,
the quality
s p e c i f y i n g the
of t h e m a i n t e n a n c e t o
checks
and t h e p e r i o d
a s n e c e s s a r y , by testing).
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3
Information
on the requirements
for routine
checks and inspections should b e
provided in accordance with Section 6 of t h e HSWA 1974 and as required by t h e
CDM Regulations. Dutyholders and users of premises should seek this information as
the basis on which to make their own assessments. The HSE advises in HSR25 that
practical experience of an installation's use may indicate the need for an adjustment to
the frequency of checks and inspections. This is a matter of judgement for the dutyholder.
BS 7 6 7 1 requires t h e designer of a n electrical installation to recommend t h e interval
to t h e first periodic inspection and insert the date of that recommendation o n t h e E1C.
However, as stated in Regulation 341 .1, wider consideration
should b e given to the
expected maintainability of a n installation, and t h e client, and perhaps t h e installer,
should also b e involved, with t h e designer taking t h e advice of other relevant persons
into account. After the first, and further periodic inspections
a n d tests, the inspector,
in conjunction with t h e client, taking into account the test results and the observations
found, will then advise on t h e period until the next inspection. Whatever inspection
and testing periods are decided u p o n must b e justifiable, as they may b e requested to
b e justified in t h e case of an accident or similar. It would not b e unreasonable for the
inspector to write supporting reasons for the period onto the inspection and test report.
3.5
Routine
checks
Electrical installations should n o t b e left without any attention for t h e periods of years
that are normally allowed between formal inspections. In domestic premises, it is
presumed that the occupier will soon notice any breakages or excessive wear and
arrange for precautions t o b e taken and repairs to b e carried out.
Commercial and industrial installations come under the EAWR. For these installations,
formal arrangements are required for maintenance and interim routine checks (as well
as for periodic inspections); there should also b e the facility to receive wear-and-tear
reports f r o m users of the premises.
The frequency and t y p e of these routine checks will depend entirely u p o n the nature
of the premises and should b e set by the electrical dutyholder. Routine checks should
include t h e items listed in Table 3.1. Table 3.2 ( i n Section 3.7) provides guidance o n
the frequency for initial interval between inspections, which m a y need to b e increased
as an installation ages.
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▼ Table 3.1 Routine checks
Activity
Check
Defects reports
All reported defects have b e e n rectified
Inspection
Look for:
(a)
(b)
(c)
(d)
(e)
breakages
wear/deterioration
signs of overheating
missing parts (covers, screws)
loose fixings
Confirm:
(a)
(b)
(c)
Operation
switchgear accessible (not obstructed)
doors of enclosures secure
adequate labelling in place
Operate:
(a)
(b)
(c)
switchgear (where reasonable)
e q u i p m e n t - switch o n and off
including RCDs (using test button)
Note that routine checks need not b e carried out by an electrically skilled person,
but should b e undertaken by somebody who is able to safely use t h e installation and
recognize defects.
There is a general ongoing requirement
to manage health and safety at work, and
electrical safety is just one area of this. To ensure that regular routine checks are m a d e
o n the electrical installation, it may b e advantageous in larger premises to combine
these with other regular checks, such as emergency lighting a n d fire alarm inspections,
general fire safety inspections, emergency exit route inspections, and so on, o n security
patrols. A system to record obvious defects should b e implemented and a simple f o r m
is all that is needed.
3.6
Required information
It is essential that t h e inspector knows and agrees with the client the extent of t h e
installation to b e inspected and any criteria regarding t h e limit of t h e inspection. This
should b e recorded.
514.9 Enquiries should b e m a d e to t h e person responsible for the electrical installation with
regard to t h e provision of diagrams, design criteria, type of electricity supply (and any
alternative supply) and earthing arrangements.
Where they exist, diagrams, charts or tables should b e m a d e available to indicate t h e
type and composition of circuits and t h e identification of protective devices for shock
protection,
isolation and switching, with a description
of the method
used for fault
protection. Unfortunately, most such records are not kept up-to-date w i t h modifications
made to the installation, and an inspector will initially need to verify the accuracy of
any such information provided.
Where there are n o records, in all but t h e simplest domestic installation, a n inspector
may first need to spend t i m e tracing installation systems and circuits and producing
basic drawings and schedules, before starting any inspection and testing work.
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3.7
Frequency of periodic inspections
644.4
The t i m e intervals between t h e recommended dates of periodic inspections and
653.4
testing require careful consideration. The date for t h e first periodic inspection and test
is required to b e considered and recommended by the installation designer, based o n
their design philosophy and maintenance advice f r o m other parties (Regulation 341.1).
The period for each subsequent periodic inspection is required to b e considered and
recommended by the inspector as part of carrying out a periodic inspection a n d test.
Regulations 644.4 and 653.4 requires the reason for selecting the interval between
the current inspection
and the next periodic inspection
to b e recorded on the EIC,
MEIWC o r EICR as relevant.
652.1
In advising the person ordering t h e work about t h e t i m e interval for t h e period for t h e
next recommended periodic inspection and test, t h e inspector is required to take into
consideration t h e individual characteristics of t h e type of installation and equipment, its
condition, use and operation, any damage and deterioration, any known maintenance
and t h e external influences to which it is subjected. The results and recommendations
of any previous periodic inspection reports should also b e considered.
The suggested initial frequencies for inspection and testing given in Table 3.2 are
recommendations
and not legal requirements.
The period
between
subsequent
inspections may b e reduced, o r occasionally increased. It is the responsibility of the
person responsible for the electrical installation to determine when the next periodic
inspection is undertaken. In making this decision, they should take appropriate advice
f r o m specialists, where necessary, t o assessthe conditions affecting t h e installation that
might lead to defects, potential damage and/or deterioration that would affect safety.
Such advice m a y include routine checks, manufacturers'
o r engineers' advice and
guidance, and periodic inspection and testing reports, with this information
assisting
the person responsible for t h e electrical installation in determining t h e maintenance
plan for t h e installation. Over time, and with practical maintenance experience, it may
b e possible to extend periodic inspection and testing intervals if t h e results of routine
checks, inspections or tests show that few faults are found and that t h e installation
is not subject to excessive deterioration. However, if faults are common, it may b e
necessary t o reduce intervals or take other action to improve maintenance and reduce
risk. Routine checks and periodic inspection and testing by an inspector are only a
part of the requirement
for maintenance;
t h e person responsible for the electrical
installation has a continuing ongoing responsibility for the safety of an installation.
Note:
Persons responsible for electrical installations are reminded of the requirements of
Regulation 4(2) of the EAWR. Undertaking routine inspection and testing of their
installationswill assist in meeting this duty.
The inspector, being a skilled person, should apply sound engineering
judgement
and experience w h e n deciding u p o n t h e intervals between inspecting and testing
an installation based u p o n t h e criteria in Regulation 6 5 2 of BS 7671. It must also b e
noted that in the event of an accident or dangerous occurrence, t h e inspector may b e
required to justify their decision.
In t h e case of domestic and commercial premises,
a change i n occupancy of the
premises may necessitate additional inspection and testing.
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651.1 The formal periodic inspection and testing should b e carried out in accordance with
Regulation 642, supplemented by tests as detailed in Regulation 643. This requires
an inspection comprising a detailed examination of the installation, carried o u t without
dismantling, or with partial dismantling as required, together with the appropriate tests
of Regulation 643 as required to comply with Regulation 651.2.
652.2
Where there is an effective management system in place for inspection and preventative
maintenance of the installation (for example, where there are competent permanent
on-site maintenance staff), periodic inspection and testing can b e replaced by an
adequate regime of continuous monitoring and maintenance of the installation and its
constituent
equipment.
However, appropriate records must b e maintained
o n site to
show that a n inspection and preventative maintenance plan is in place and is being
adhered to.
Although periodic inspection
a n d testing is primarily aimed at keeping an electrical
installation in a safe state, it can also have other financial benefits, such as identifying
possible upcoming equipment failures that could interrupt production, providing advice
o n energy saving, a n d reducing running costs. It must also b e noted that while this
Guidance Note is concerned with periodic inspection and testing for t h e maintenance
of safety of general electrical installations, there are other specialist parts of an electrical
installation, such as plant controls, fire alarms and emergency lighting, that also require
separate periodic inspection and testing by specialists for t h e maintenance of safety.
▼ Table 3.2 Recommended
initial frequencies
of inspection of electrical installations
Notes
Routine check (see
Section 3.5)
Maximum initial
period between
inspections and
testing (Note 8)
Domestic accommodation:
general
—
Change of
occupancy/10 years
Domestic accommodation:
rented houses a n d flats
1 year
5 years
1,2, 10, 12
Residential accommodation
(HMOs): halls of residence,
nurses' accommodation, etc.
1 year
5 years
1 , 2 , 10, 11
Commercial
1 year
5 years
1 , 2 , 3, 4
6 months
5 years
1,2, 6
Industrial
1 year
3 years
1,2
Offices
1 year
5 years
1,2
Shops
1 year
5 years
1,2
Laboratories
1 year
5 years
1,2
Type of installation
General installation
Educational establishments
Medical locations (see Appendix 11 t o the IET Guide to Electrical Installations
Medical Locations)
in
Hospitals a n d medical clinics:
Goup 0
1 year
5 years
1,2
Hospitals a n d medical clinics:
Group 1 a n d Group 2
6 months
1 year
9
Guidance Note 3 : Inspection & Testing
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Routine check (see
Section 3.5)
Maximum initial
period between
inspections and
testing (Note 8)
Notes
Cinemas
1 year
1 -3 years
2, 6
Church installations
1 year
5 years
2
Leisure complexes (excluding
swimming pools)
1 year
3 years
1,2, 6
Places of public entertainment
1 year
3 years
1,2, 6
Restaurants, hotels a n d
short-term lets
1 year
5 years
1,2, 6
Theatres
1 year
3 years
2, 6
Public houses
1 year
5 years
1,2, 6
Village halls/community
centres
1 year
5 years
1 ,2
Type of installation
Buildings open to the public
Special and specific installations
Agricultural
and horticultural
Caravans
Caravan parks
Highway power supplies
Marinas
Mobile a n d transportable units
according to Section 717 of
BS 7671
(a) Pre-delivery
(b) On-site/in-use
(see above for medical locations)
1 year
3 years
1,2
1 year
3 years
7, 12
6 months
1 year
1 , 2 , 6 , 12
as convenient
6 - 8 years
4 months
1 year
1,2
13
Prior to delivery, or 1
year if in storage
Prior to delivery,
or 1 year if i n storage
On connection at site,
then dependent o n
On connection
use
at site,
then dependent
use
on
Fish farms
4 months
1 year
1,2
Swimming pools
4 months
1 year
1,2,6
Emergency lighting
daily/monthly
3 years
2, 3, 4
Fire alarms
daily/weekly
1 year
2, 4, 5
Launderettes
monthly
1 year
1,2, 6
Petrol filling stations
1 year
1 year
1,2, 6
3 months
3 months
1,2
Construction site installations
Notes:
1
2
3
4
5
6
7
116
Particular care m u s t b e taken t o comply w i t h t h e Electricity Safety, Quality a n d
Continuity Regulations (ESQCR) (as amended).
Regulation 4 of t h e E A W R a n d HSR25.
See BS 5266-1 : 2 0 1 6 Emergency lighting. Code o f practice for the emergency lighting of
premises a n d t h e IET Electrician's Guide to Emergency Lighting.
Other intervals are r e c o m m e n d e d f o r t e s t i n g operation of batteries and generators.
See BS 5839-1 : 2017 Fire detection and fire alarm systems for buildings. Code o f practice
for design, installation, commissioning
and maintenance
of systems in non-domestic
premises and the IET Electrician's Guide to Fire Detection and Fire Alarm Systems.
Local Authority conditions of licence. There is specific legislation listed i n BS 7 6 7 1
relating to cinemas a n d theatres.
It is r e c o m m e n d e d that a caravan is inspected a n d tested every three years, w i t h this
period reduced t o every year if it is used frequently (see Regulation 721.514.1 and Fig 721
(Instructions for electricity supply)).
Guidance Note 3: Inspection & Testing
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8
The person carrying out subsequent inspections may recommend that the interval between
future inspections be increased or decreased as a result of the findings of their inspection.
9 Medical locations shall have their isolating transformer equipment inspected and tested
for functionality, as well as alarms, etc. Every third year the output leakage current of the
IT isolating equipment shall be measured. Measurements to verify that the resistance
of the supplementary equipotential bonding is within the limits stipulated by Regulation
710.415.2.2 should be carried out annually. In addition, in Group 2 Medical locations
complete functional tests of the insulation monitoring devices (IMDs) associated with
the medical IT system including insulation failure, transformer high temperature,
overload, discontinuity and the audible/visual alarms linked to them should be
conducted annually.
10 The Landlord and Tenant Act 1985 requires that properties under the Act have their
services maintained. Periodic inspection and testing is the lET's recognized method of
demonstrating this.
1H The Management of Houses in Multiple Occupation (England) Regulations and the
Management of Houses in Multiple Occupation (Wales) Regulations.
12 The Electrical Safety Standards in the Private Rented Sector (England) Regulations 2020
requires landlords in the private rented sector in England to have a rental property
inspected and tested every five years and supply a copy of the report to the tenant
within 28 days. Any remedial works or further investigation must be completed within
2 8 days, and confirmation provided in writing to the tenant, and local authority if
required, within 28 days of completion of this work. There are similar requirements in all
devolved nations, and guidance is available on the relevant Government website.
13 Mobile and transportable units should be inspected and tested at least every
12 months. Mobile and transportable units that are connected to an independent source
of electricity at site should be inspected and tested on connection. In use, mobile and
transportable units should be at periods suitable for the environment in which it is
being used, for example every three months in a construction site environment, up to a
maximum of 12 months between inspection and testing.
Any landlord (of an H M O or other occupancy) may b e considered to have duties under
the EAWRdue to their responsibilities under Section 3 of t h e HSWA 1974 (relating, for
example, to the c o m m o n areas of a set of flats). In Scotland, the private rented sector
has legal requirements to maintain the electrical installation. Landlords are required by
law to ensure that the electrical installation in a rented property is safe w h e n tenants
m o v e in and is maintained in a safe condition throughout its duration and that an H M O
has a periodic inspection carried o u t o n the property every five years.
(The definition of a H M O is difficult, but it hinges o n whether the persons living i n
the house are related - as in a large family residence - or completely separate, as in
a block of flats.)
3.8
Requirements for periodic inspection and testing
3.8.1
Process: prior to carrying
out inspection
and testing
Prior to carryingout t h e inspection, the inspector will need to meet with the client o r
the client's representative to agree the scope a n d nature of t h e work required and the
programme and to highlight likely items that require isolation.
Consultation
with
t h e client
or t h e client's representative
prior to t h e periodic
inspection and testing work being carried out is essential t o determine the access and
any disruption to the normal work in the premises. The inspector will also n e e d to
ascertain, and b e appraised of, particular health and safety requirements
(as dangerous
processes may b e being carried out), security and access and fire safety requirements,
a n d to determine
the degree of electrical disconnection that will b e acceptable. To
assist with the planning of the detailed inspection and testing, any existing drawings,
schedules and documentation of t h e installation should b e available; some initial
Guidance Note 3: Inspection & Testing
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validation of these will b e necessary. In addition, the extent of previous maintenance
a n d routine tests, along with documentation including t h e original design a n d E I C , a n d
certificates for any other electrical works that have b e e n carried out in the premises, if
available, should b e provided to the inspector.
For safety, it is necessary to carry out a visual inspection of t h e installation before
testing or opening enclosures, removing covers, etc. So far as is reasonably practicable,
t h e visual inspection must verify that the safety of persons, livestock and property is
not endangered.
3.8.2
General
procedure
Note:
The following advice is not applicable to domestic or simple installations, as the extent
and method of inspection and testing is rudimentary in such installations compared
with more complex installations.
Although there are various approaches to carrying out inspection and testing, one
suggested method
is to first obtain an overview
of the installation, ideally f r o m
diagrams a n d charts, as well as from a simple 'walk-round' survey prior to starting the
full inspection. This will enable the inspector to b e able to plan the inspection and to
identify items that require isolation, etc. M o s t importantly, this initial survey will enable
the inspector to set sample sizes, (see Section 3.8.3).
651.1
Where diagrams, charts or tables are not available, a degree of exploratory work may
b e necessary so that inspection and testing can be carried out safely and effectively;
this may include a survey to identify switchgear, controlgear and the circuits they control.
Indeed, for m o r e involved installations without design information,
such as, diagrams
or charts, t h e client should b e advised that such diagrams require producing in order
to plan and conduct the inspection and testing. Alternatively, where the inspector
considers that it is safe to proceed, the inspection can commence, but may b e limited to
visual inspection. The production of diagrams and charts can be called for on the EICR.
651.2
Note should b e m a d e of any k n o w n changes in environmental conditions or building
structure, and of any additions or alterations. The inspector may need to consider
whether such changes have affected t h e suitability of wiring systems and other
equipment f o r t h e i r present load, location, and m e t h o d of installation.
During t h e inspection, opportunity should b e taken to identify dangers that might arise
during t h e testing. Any location and equipment
for which safety precautions may b e
necessary should b e noted and the appropriate steps taken.
A thorough inspection should b e made of all electrical equipment that is not concealed,
and should include the accessible internal condition of a sample of the equipment.
The external condition should b e noted and, if damage is identified or if the degree of
protection has been impaired, this should b e recorded o n t h e Schedule of Inspections
appended to the Report. The inspection should include a check o n t h e condition
of
electrical equipment and material, taking into account any available manufacturer's
information, with regard to the following:
(a) safety;
(b) age;
(c) damage and defects;
(d) corrosion and external influence®;
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Guidance Note 3: Inspection & Testing
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(e) overloading
(f)
(signs of);
wear a n d tear a n d environment;
(g) change
i n u s e o f t h e l o c a t i o n i n w h i c h it i s i n s t a l l e d ; a n d
(h) suitability
f o r continued
use.
T h e a s s e s s m e n t o f c o n d i t i o n s h o u l d t a k e a c c o u n t o f k n o w n changes
influencing
a n d a f f e c t i n g e l e c t r i c a l safety, f o r example,
plumbing
i n conditions
o r s t r u c t u r a l changes.
W h e r e parts of a n electrical installation are excluded f r o m t h e s c o p e of a periodic
inspection
a n d test, they should
b e identified
in the 'Extent
a n d limitations'
section
of
t h e Report.
Periodic
inspection
a n d testing
should
b e u n d e r t a k e n i n such a w a y as to minimize
d i s t u r b a n c e of t h e i n s t a l l a t i o n a n d i n c o n v e n i e n c e t o the user. Where
it i s n e c e s s a r y
t o d i s c o n n e c t p a r t o r t h e w h o l e of a n i n s t a l l a t i o n i n o r d e r to c a r r y o u t a test,
disconnection
should
b e made
at a time
the
a g r e e d with the user a n d f o r the minimum
p e r i o d n e e d e d to carryout the test. Where m o r e than o n e test necessitates a disconnection,
where possible, these tests should
643.3.2
b e made during one disconnection
period.
A c a r e f u l c h e c k s h o u l d b e m a d e of t h e t y p e of e q u i p m e n t o n site s o t h a t t h e n e c e s s a r y
p r e c a u t i o n s c a n b e taken, w h e r e c o n d i t i o n s r e q u i r e , t o d i s c o n n e c t o r s h o r t - o u t
electronic
a n d other
equipment
t h a t might
b e damaged
by testing.
Special c a r e must
b e taken w h e r e control a n d protective devices contain electronic c o m p o n e n t s .
3.8.3 Setting inspection and testing samples
T h e i n s p e c t o r m u s t b e f a m i l i a r w i t h s e t t i n g b o t h i n s p e c t i o n a n d t e s t i n g s a m p l e sizes,
a s c a r r y i n g o u t 100 7o inspection
a n d unachievable
o r testing
i n a n e l e c t r i c a l i n s t a l l a t i o n is unrealistic
h o w e v e r m a y be a c h i e v a b l e f o r d e f i n e d p a r t s of it. Information
is
p r o v i d e d i n this s e c t i o n a n d i n t h e relevant s a m p l i n g table, Table 3 . 3 .
As pointed
o u t in S e c t i o n 3.8.3,
o n e r e c o m m e n d e d p r o c e d u r e i s f o r the
inspector
t o carry o u t a n initial w a l k - r o u n d s u r v e y t o e s t a b l i s h initial s a m p l e sizes a t v a r i o u s
p o i n t s throughout
the
installation. T h e detailed
s a m p l e size i s a d j u s t e d upwards
i f necessary,
inspection
depending
is then
s t a r t e d a n d the
u p o n the results
obtained.
W h e r e practicable, s a m p l e s s h o u l d b e selected t h a t are representative of t h e w h o l e
installation.
Parts of the i n s t a l l a t i o n that, in the i n s p e c t o r ' s experience,
a r e m o r e likely
to be p r o b l e m a t i c , s h o u l d b e p r i o r i t i z e d .
Discussions
of s a m p l i n g a n d s a m p l e size selection
b e r a t h e r simplistic,
while
in practice,
a r e generally
s i m p l i f i e d and tend to
m a t t e r s a r e usually quite different.
As discussed
previously, a n initial s u r v e y of t h e p r e m i s e s m u s t b e c a r r i e d o u t ; i t i s r e a s o n a b l y likely,
a s with
m o s t buildings,
t h a t different
things
will have been
in i t s life. It m a y b e n e c e s s a r y to t a k e separate
done to it a t v a r i o u s t i m e s
s a m p l e s of the s a m e thing
indifferent
areas. For e x a m p l e , i n a f a c t o r y , t h e c o n d i t i o n o f a f l u o r e s c e n t l u m i n a i r e installation i n
the o f f i c e a r e a i s unlikely
to b e representative
i n s t a l l a t i o n in t h e production
of the condition
of a f l u o r e s c e n t luminaire
area, even if they a r e the s a m e type of luminaire.
Guidance N o t e 3 : I n s p e c t i o n & Testing
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Inspectors will require all of their experience in setting sample locations and sizesand
should consider:
(a) t h e approximate age and probable condition of the electrical installation in the
area being inspected;
(b) any electrical installation work carried out since the last inspection and test;
(c) any differences in the installation in the area (part of it may have been
refurbished or taken from another area);
(d) the type a n d usage of the installation o r part thereof in that area (part of it may
have b e e n used for another purpose previously);
(e) the ambient environmental
ambient environmental
conditions in t h e area and any differences in t h e
conditions over the area;
(f) the apparent effectiveness of ongoing maintenance, if any;
(g) the period of t i m e elapsed since previous inspection/testing;
(h) the size of the installation and any differences i n the ambient environmental
conditions over the area;
(i) consultation with the installation owner; and
(j) the quality of records such as EICs, MElWCs, previous periodic
reports, maintenance
records, site plans/drawings
inspection
and data sheets relating to
installed equipment.
It should b e noted that the initial sample size is based only o n a visual pre-inspection
and consultation of records. Further, what may at first appear to b e good, for example,
the quality of maintenance, may turn o u t to b e poor during the detailed inspection
and testing.
In determining
the sample size, it should b e noted that the minimum
to get meaningful
population
size
results is 1 0 0 according to statistical sampling theory. That means
that inspection and testing as a whole, should cover at least 100 points on electrical
equipment.
The term electrical equipment
is defined in BS 7671 as follows:
El lectrica! e q u i p m e n t ( a b b r : Equipment). Any item for such purposes as generation,
conversion, transmission, distribution o r utilization of electrical energy, such as
machines, transformers, apparatus, measuring instruments, protective devices, wiring
systems, accessories, appliances and luminaires.
For very small installations such as those in some domestic premises, this principle is
likely to m e a n that most electrical equipment
forming part of the fixed installation is
inspected a n d tested as appropriate. For example, a small domestic installation may
only have four circuits each with less than ten accessories connected; t h e total number
of items of electrical equipment, including the consumer unit and circuit wiring, is likely
to b e well under 100, and, because it is practicable, all items are likely to b e included
in the inspection and test. There should certainly b e n o sample of circuits made in
such premises.
In larger installations, such as those in commercial
or industrial
premises,
it is
recommended to change t h e sample to b e inspected and/or tested between periodic
inspection and test visits. To facilitate this, the specific equipment
sampled should b e
clearly identified in t h e records. If this is not done, due t o large population sizes f r o m
which samples are taken, it is possible that some parts of t h e installation would rarely,
if ever, b e inspected and/or tested.
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Guidance Note 3: Inspection & Testing
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▼ Figure 3.1 Suggested procedure for setting a n d adjusting sample sizes
periodic
verification
required
conduct pre
inspection survey
and establish sample
size
select samples for
inspection and
testing based on
sample size
information
available on
samples previously
selected?
select samples for inspection
and testing based on sample
size, avoiding previously
selected samples where
appropriate
yes
concentrate on circuits and
equipment most likely to show
defects
carry out
inspection and
testing on
samples selected
intermediate/poor/
indeterminate results
good results
status of results
no
increase sample
size or discuss
with client
whether more
in-depth
investigation is
necessary
sample size to be
increased?
yes
final report
Where the inspection or testing of a sample yields poor or unacceptable results, this
would suggest that similar problems might exist elsewhere in uninspected or untested
items. The inspector will t h e n need either to increase the sampling or refer back to
the client; it may b e that the inspector recommends that 100 °/otesting is carried o u t
in that area.
The principle of this is indicated in Figure 3.1.
G u i d a n c e N o t e 3: Inspection
© The Institution
of Engineering
& Testing
and Technology
121
As an example, consider the testing of final circuits at a distribution board with a
sample size of 10 7o of the lighting circuits. Suppose that more than one of these
circuits was found to have an unacceptably high earth fault loop impedance (EFLI),
with a relatively low EFLIatthe incoming terminals to the distribution board itself, and
that there were no apparent factors to suggest why the final circuit values were high.
It would be remiss to complete the EICRby using just this 10 7o sample and stating
that improvements were required for these circuits. It would be far more appropriate
to increase the sample size or to recommend that all circuits at the distribution board
were tested, based on the initial findings.
If relatively small sample sizes are chosen, it is important that these are representative
of the complete installation. Similarly, if a repeat periodic inspection is undertaken
using a sampling system, then a different sample, again representative of the complete
installation, must be chosen. Therefore, previous periodic inspection and test records
should be consulted prior to commencement of a sample inspection and test.
Suggested sample sizes for visual inspections are provided in Table 3.3; suggested
sample sizes for testing are discussed in Section 3.10.1 of this Guidance Note and in
Table 3.4.
V
T a b l e 3 . 3 Range of samples for inspection
Item
Suggested minimum
sample size (notes 1, 2)
Typical checks
Main switchgear external
inspection
100%
Signs of damage,
overheating or ageing
Main switchgear internal
sections and cable
terminations
Ideally 100 % but not less
than 2 0 % (note 2)
Signs of overheating, ageing,
check tightness of terminals
Main switchgear internal
inspection of circuit-breaker
connections a n d control
sections
Ideally 1 0 0 % b u t n o t less
than 2 0 %
Signs of overheating, ageing,
check tightness of terminals
Final circuit distribution
boards
Ideally 100 % but not less
than 25 % (note 4)
Signs of overheating, ageing,
check tightness of terminals
Final circuit accessories
B e t w e e n 1 0 % to 1 0 0 %
(note 3). Samples selected
should cover all final circuits
in small installations.
Damage, signs of
overheating
Earthing and protective
bonding conductors
100%
Presence of conductors and
tightness of
terminations
Notes:
1
Where t h e inspection o f a sample yields p o o r or unacceptable results, this w o u l d
suggest that similar problems m a y exist elsewhere i n t h e uninspected items. T h e
inspector will n e e d either t o increase t h e sampling or refer back t o t h e client; it m a y b e
2
3
4
5
122
that t h e inspector r e c o m m e n d s that 1 0 0 % inspection is carried o u t i n that area.
1 0 0 % where practicable.
Generally, it is less appropriate to apply small sample sizing to the inspection of
socket-outlets compared w i t h samples for lighting, as i t is m o r e likely that user
e q u i p m e n t will b e hand-held presenting a greater risk for potential electric shock.
D o not 'sample samples', resulting in a very l o w overall sampled installation. Samples
m u s t b e representative. If i t is decided t o sample, for example, sub-main cables at
10 7o,then further sampling should not b e applied to t h e final circuit distribution boards
o n these circuits.
One easy way t o remember sampling is to reflect o n the fact that where just 1 0 % of final
circuits have b e e n inspected, this actually means that 9 0 % have not b e e n inspected.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
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Whenever samples are taken, and whatever sample size is utilized, the inspector must
remember
that t h e requirement
installation being inspected
of the Report is to say whether or not t h e electrical
(subject t o any agreed limitations)
is suitable or not for
continued use. The inspector m u s t carry out sufficient inspection and testing to allow
t h e m to make that judgement, i n many dwellings and smaller commercial installations,
sampling would b e largely inappropriate and should never o m i t entire circuits.
3.9
Periodic inspection
3.9.1 Example checklist of items that require inspection
Appx6
The following is a copy of the checklist in Appendix 6 of BS 7671, which lists items at
various locations within a n installation that may require inspection. The items in this
checklist are examples; t h e list is not exhaustive.
ELECTRICAL INTAKE EQUIPMENT
(VISUAL INSPECTION
Where inadequacies in intake equipment
are encountered,
ONLY)
it is recommended
that
the person ordering t h e report informs the appropriate authority.
•
•
•
Service cable
Service head
Earthing arrangements (where provided, for example TN-C-S and TN-S
systems, b u t not TT systems)
•
Meter tails (on both supplier and consumer side of the meter)
•
Metering equipment
•
Isolator (where present)
Note:
It is important for the inspector to provide information about inadequacies with
electrical intake equipment, along with any recommendation to inform the relevant
authority, to the person ordering the report, in writing to cover liability.
PRESENCE OF ADEQUATE ARRANGEMENTS
FOR PARALLEL O R SWITCHED
ALTERNATIVE SOURCES
•
Adequate arrangements where a generating set operates as a switched
alternative to t h e public supply (551.6)
•
Adequate arrangements where a generating set operates in parallel with t h e
public supply (551.7)
AUTOMATIC
•
DISCONNECTION
Main earthing bonding arrangements (411.3; Chap 54)
1
Presence of distributor's earthing arrangement (542.1.2.1; 542.1.2.2), or
2
presence of installation earth electrode arrangement (542.1.2.3)
Adequacy of earthing conductor size (542.3; 543.1.1)
3
Adequacy of earthing conductor connections (542.3.2)
4
Accessibility of earthing conductor connections (543.3.2)
5
Adequacy of main protective bonding conductor sizes (544.1)
6
Adequacy and location of m a i n protective bonding conductor connections
(543.3.2;
7
•
OF SUPPLY
544.1.2)
Accessibility of all protective bonding connections (543.3.2)
8
Provision of earthing/bonding labels at all appropriate locations (514.13)
FELV- requirements satisfied (411.7; 411.7.1)
Guidance Note 3: Inspection & Testing
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3
OTHER METHODS
O F PROTECTION (where any of the methods listed below are
employed details should b e provided o n separate pages)
•
Non-conducting location (418.1)
•
Earth-free local equipotential bonding (418.2)
•
Electrical separation (Section 413; 418.3)
•
Double insulation (Section 412)
•
Reinforced insulation (Section 412)
DISTRIBUTION EQUIPMENT
•
Adequacy of working space/accessibility to equipment (132.12; 513.1)
•
Security of fixing (134.1.1)
•
Condition of insulation of live parts (416.1)
•
Adequacy/security of barriers (416.2)
•
Condition of enclosure(s) in terms of fire rating etc (; 421 .1.6; 421.1.201 ; 526.5)
•
Enclosure not damaged/deteriorated so as to impair safety (651.2)
•
Presence and effectiveness
•
Components
of obstacles (417.2)
are suitable according to manufacturers'
assembly instructions or
literature (536.4.203)
•
Presence of main switches),
linked where required (462.1; 462.1.201; 462.2)
(functional check) (643.10)
•
Operation o f main switches)
•
Manual operation of circuit-breakers, RCDs and AFDDsto prove functionality (643.10)
•
Confirmation
that integral test button/switch
causes RCD(s) to trip when
operated (functional check) (643.10)
•
RCD(s) provided for fault protection, where specified (411.4.204; 411.5.2; 531.2)
•
RCD(s) provided for additional protection, where specified (411.3.3; 415.1)
•
Confirmation
overvoltage protection (SPDs) provided where specified
(534.4.1.1)
•
•
Presence of RCD six-monthly test notice where required (514.12.2)
Presence of diagrams, charts or schedules at or near equipment, where
required (514.9.1)
•
Presence of alternative supply warning notice, where required (514.15)
Labels for multiple supplies should b e provided at:
1
The origin
2
The meter position, if remote f r o m origin
3
The distribution board to which the alternative/additional sources are
connected
4
All points of isolation of ALL sources of supply
•
Presence of next inspection recommendation label (514.12.1)
•
Presence of other required labelling (Section 514)
•
Selection of protective device(s) and base(s); correct t y p e and rating (411.3.2;
411.4,.5, .6; Sections 432, 433, 434)
•
Single-pole protective devices in line conductors only (132.14.1, 530.3.2; 643.6)
•
Protection against mechanical damage where cables enter equipment
•
Protection against electromagnetic effects where cables enter ferromagnetic
(522.8.1; 522.8.5; 522.8.11)
enclosures (521.5.1)
Confirmation that ALL conductor connections, including connections to busbars, are
correctly located in terminals and are tight and secure (526.1)
The
use of individual components in a distribution board or consumer unit
assembly complying
their compatibility
controlgear assembly.
124
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© The Institution
of Engineering and Technology
with their respective product
standard(s) does not indicate
when installed with other components
in an LV switchgear and
3
Incorporated components
inside the assembly can be f r o m different manufacturers.
It is essential that all incorporated components have their compatibility for the
final enclosed arrangements verified by t h e original manufacturer
of the assembly
and are assembled i n accordance with their instructions, for example, those of the
consumer
unit or distribution
board manufacturer.
The original manufacturer is
t h e organization that carried out t h e original design and t h e associated verification
of the LV switchgear and controlgear assembly to the relevant part of the BS EN
61439 series. If an assembly deviates from its original manufacturer's instructions, or
includes components n o t included in t h e original verification, the person introducing
the deviation becomes the original manufacturer, with the corresponding obligations.
The inspector may wish to note such assemblies for further investigation.
Consumer unit standards have also evolved over the years to provide co-ordinated
'conditional ratings'.
1
BS 5486-13: 1979 had a 6 kA, 10 kA, o r 16 kA conditional rating as part
of a British Standard. The inspector therefore needs to check t h e label or
instructions for CM6, CM10 or CM16.
2
BS 5486-13: 1989 had a 16 kA conditional rating as part of a British
Standard. BS 5486-13 was withdrawn and replaced by B S E N 60439-3: 1991.
3
BS EN 60439-3: 1991 had UK National deviation Annex ZA 16 kA
conditional rating. B S E N 60439-3:
1991 was withdrawn and replaced by
4
BS EN 60439-3: 2012.
BS EN 61439-3: 2012 has UK National deviation Annex ZB 16 kA
5
BS EN 61439-3: 2012 (incorporating
conditional rating.
December
corrigenda
September 2013 a n d
2015) is the only current version for new installations, but the
older equipment may still b e in use in installations.
DISTRIBUTION CIRCUITS
•
Identification
•
Cables correctly supported throughout
of conductors (514.3.1)
their run (521.10.202; 522.8.5)
•
Condition of insulation of live parts (416.1)
•
Non-sheathed
•
(521.10.1)
Suitability of containment
•
Cables correctly terminated i n enclosures (Section 526)
•
Confirmation
•
busbars, are correctly located in terminals and are tight and secure (526.1)
Examination of cables for signs of unacceptable thermal or mechanical
•
damage/deterioration
(421 .1 ; 522.6)
Adequacy of cables for current-carrying capacity with regard for the type and
cables protected by enclosure in conduit, ducting or trunking
systems for continued use (including flexible
conduit) (Section 522)
that ALL conductor connections,
including connections to
nature of installation (Section 523)
•
Adequacy of protective devices: type and rated current for fault protection (411.3)
•
Presence and adequacy of circuit protective conductors (411 .3.1.1; 543.1 )
•
•
Coordination between conductors and overload protective devices (433.1 ; 533.2.1)
Cable installation methods/practices w i t h regard to the type and nature of
•
Where exposed to direct sunlight, cable of a suitable type (522.11.1)
•
Cables concealed
installation and external influences (Section 522)
under floors, above ceilings, in walls/partitions
less than
5 0 m m f r o m a surface, and in partitions containing metal parts
1
installed in prescribed zones (see Section D. Extent and
(522.6.202)
limitations)
or
Guidance Note 3 : Inspection
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3
2
incorporating
earthed armour or sheath, o r run within earthed wiring
system, o r otherwise protected against mechanical damage by nails,
screws and t h e like (see Section D. Extent and limitations)
•
(522.6.204)
Provision of fire barriers, sealing arrangements and protection against thermal
effects (Section 527)
•
Band II cables segregated/separated
•
•
Cables segregated/separated f r o m non-electrical services (528.3)
Condition of circuit accessories (651.2)
f r o m Band I cables (528.1)
•
Suitability o f circuit accessories for external influences (512.2)
•
Single-poleswitchingor protective devices in line conductors only (132.14.1 ;530.3.3)
•
Adequacy of connections, including cpcs, within accessories and to fixed
and stationary equipment
- identify/
record numbers and locations of items
inspected (Section 526)
•
Presence, operation and correct location of appropriate devices for isolation
and switching (Chapter 46; Section 5 3 7 )
•
General condition of wiring systems (651.2)
•
Temperature rating of cable insulation (522.1.1; Table 52.1)
FINAL CIRCUITS
•
Identification
•
Cables correctly supported throughout
of conductors (514.3.1)
•
Condition of insulation of live parts (416.1)
•
Non-sheathed cables protected by enclosure in conduit, ducting or trunking (521.10.1 )
•
Suitability of containment
their run (521.10.202; 522.8.5)
systems for continued
use (including flexible
conduit) (Section 522)
•
Adequacy of cables for current-carrying capacity with regard for the t y p e and
nature of installation (Section 523)
•
•
Adequacy of protective devices: type and rated current for fault protection (411.3)
Presence and adequacy of circuit protective conductors (411.3.1.1; 543.1)
•
Co-ordination between conductors and overload protective devices (433.1 ; 533.2.1 )
•
Wiring system(s) appropriate for the t y p e and nature of t h e installation and
•
Cables concealed under floors, above ceilings, in walls/partitions,
external influences (Section 522)
adequately
protected against damage (522.6.201; 522.6.202; 522.6.203; 522.6.204)
1 installed in prescribed zones (see Section D. Extent and limitations)
(522.6.202)
2
incorporating earthed armour or sheath, o r run within earthed wiring
system, or otherwise protected against mechanical damage by nails,
screws and t h e like (see Section D. Extent and limitations)
(522.6.201;
522.6.204)
•
Provision of additional protection by 3 0 m A RCD
1
*for all socket-outlets of rating 3 2 A or less unless a documented
risk
assessment confirms an RCD is not necessary (411.3.3)
2
*for the supply of mobile equipment
not exceeding 3 2 A rating for use
outdoors (411.3.3)
3
*for cables concealed in walls at a depth of less than 5 0 m m (522.6.202;
4
522.6.203)
*for cables concealed i n walls/partitions containing metal parts regardless
of depth (522.6.203)
5
•
*for final circuits supplying luminaires within dwellings (411.3.4)
Suitability of equipment in terms of IP and fire ratings (416.2; 421.1; 421. 1.201; 526.5)
•
Enclosurenot damaged/deteriorated during installation so as to impair safety (134.1.1)
•
Provision of fire barriers, sealing arrangements and protection against thermal
effects (Section 527)
126
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© The Institution of Engineering and Technology
3
•
Band II cables segregated/separated f r o m Band I cables (528.1)
•
Cables segregated/separated f r o m non-electrical services (528.3)
•
Termination of cables at enclosures - identify/record numbers a n d locations
of items inspected (Section 526)
1
Connections
2
N o basic insulation of a conductor visible outside enclosure (526.8)
under no undue strain (526.6)
3
4
Connections of live conductors adequately enclosed (526.5)
Adequately connected at point of entry to enclosure (glands, bushes etc.)
(522.8.5)
•
Condition of accessories including socket-outlets, switches and joint boxes (651.2)
•
Suitability of accessories for external influences (512.2)
•
Single-poleswitchingor protective devices in line conductors only (132.14.1;530.3.3)
Note:
*Older installations designed prior to BS 7671:2018 may not have been provided
with RCDsfor additional protection.
ISOLATION
•
AND SWITCHING
Isolators (Sections 460; 537)
1
2
Presence and condition of appropriate devices (462; 537.2.7)
Acceptable location - state if local or remote f r o m equipment
in question
(Section 462; 537.2.7)
3
Capable o f being secured in the OFF position (462.3)
4
Correct operation verified (643.10)
5
Clearly identified by position and/or durable marking (537.2.6)
6
Warning notice posted in situation where live parts cannot b e isolated by
t h e operation of a single device (514.11.1:537.1.2)
•
Switching off for mechanical maintenance (Section 464; 537.3.2)
1
2
Presence and condition of appropriate devices (464.1; 537.3.2)
Acceptable location - state if local o r remote f r o m equipment in question
(Section 462; 537.2.7)
•
•
3
Capable of being secured in t h e OFF position (462.3)
4
Correct operation verified (functional check) (643.10)
5
Clearly identified by position and/or durable marking (537.3.2.4)
Emergency switching/stopping
(465; 537.3.3)
1
Presence and condition of appropriate devices (465.1; 537.3.3)
2
Readily accessible for operation where danger might occur (537.3.3.6)
3
Correct operation verified (643.10)
4
Clearly identified by position and/or durable marking (537.3.3.6)
Functional switching (463.1; 537.3.1)
1
2
Presence of appropriate devices (537.3.1.1; 537.3.1.2)
Correct operation verified (537.3.1.1; 537.3.1.2; 643.10)
CURRENT-USING
EQUIPMENT
(PERMANENTLY
CONNECTED)
•
Suitability for t h e environment and external influences (512.2)
•
Security of fixing (134.1.1)
•
Cable entry holes in ceilings above luminaires, sized or sealed so as to restrict
the spread of fire (527.2)
•
•
Provision of undervoltage protection, where specified (Section 445)
Provision of overload protection, where specified (Section 433; 552.1)
•
Recessed luminaires (downlighters)
•
1
Correct t y p e of lamps fitted (559.3.1)
2
Installed to minimize build-up of heat (421.1.2; 559.4.1)
Adequacy of working space/accessibility to equipment
(132.12; 513.1)
Guidance
© The Institution
Note
3 : Inspection
& Testing
of Engineering a n d Technology
127
3
PART 7 SPECIAL INSTALLATIONS OR LOCATIONS
•
If any special installations o r locations are present, list t h e particular
inspections applied.
Where Special Installations or Locations relating to a particular Section of Part 7, an
additional inspection schedule
) should b e provided on separate pages.
3.10 Periodic testing
3.10.1
General
651.1 The periodic testing is supplementary to the inspection of the installation: see Section 3.8.1.
The same range and level of testing as for initial testing is not necessarily required, or
indeed possible, installations that have been previously tested and for which there are
comprehensive records of test results may not need the same degree of testing as
installations for which n o such records exist.
651.5 Periodic testing may cause danger if t h e correct procedures are not applied. Persons
carrying out periodic testing must b e competent in the use of t h e instruments
employed and have adequate knowledge and experience of the t y p e of installation
(see Section 3.8.1).
The inspector will n e e d t o set a sample size for testing. Notes o n the principle of this
are included in Section 3.8.3, which should b e studied together with the guidance o n
suggested tests in Table 3.4.
Where a sample test indicates results significantly different
f r o m those previously
recorded, further investigation is necessary. In addition, if during t h e course of testing
a sample, significant errors are found that suggest that the same problems might exist
in untested items, the inspector should take appropriate action by either increasing
the sampling or by referring back to the client regarding t h e matter; it may b e that the
inspector recommends
that 100 °/otesting is carried out in that area. This principle is
mentioned earlier, in Figure 3.1.
3.10.2
Tests to be made
651.2 The tests considered appropriate by t h e person carrying out the inspection should
b e carried out in accordance with t h e recommendations in Table 3.4 a n d considering
Section 3.8.1 to 3.8.3 of this Guidance Note.
See Section 2.6 of this Guidance Note for test methods, noting that alternative methods
m a y b e used, provided they give reliable results.
▼ Table 3.4 Testing t o b e carried o u t w h e r e practicable o n existing installations
(see Notes 1 and 2)
Test
Recommendations
Continuity
of protective
conductors
Accessible exposed-conductive-parts of current-using equipment
accessories (notes 4 a n d 5 )
Continuity
of bonding
conductors
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(a)
(b)
_________________________
Main protective bonding conductors to
extraneous- conductive-parts
Supplementary bonding conductors
and
|
3
Test
Recommendations
Continuity of
ring final circuit
conductors
Where there are records o f previous tests, this test m a y n o t b e
necessary unless there m a y have been changes m a d e to t h e ring final
circuit
Polarity
At the following
(a)
(b)
(c)
(d)
(e)
_______________________
positions:
origin of the installation
distribution boards
accessible socket-outlets
extremity of radial circuits
lighting circuits
Where there are records of previous tests, this test m a y not b e
necessary unless there m a y have been changes to the circuit.
EFLI
At t h e following positions:
(a)
(b)
(c)
(d)
origin of t h e installation
distribution boards
accessible socket-outlets
extremity o f radial circuits
Insulation resist
ance
If tests are to b e m a d e :
Earth electrode
resistance
If tests are t o b e made:
(a)
(a)
between live conductors (connected together, where
applicable) and Earth at main a n d final distribution boards
(note 6)
test each earth electrode o r group of electrodes separately,
w i t h t h e test links removed, a n d with t h e installation
isolated f r o m t h e supply source
Functional tests
RCDs
Tests as required b y Regulation 643.1, followed
integral test button
by operation
of the
Functional tests of
circuit-breakers,
isolators a n d
switching devices
a n d other functional
tests where
necessary
Manual operation to confirm that t h e devices disconnect t h e supply,
including functional test of AFDDsthat have a test button, by pressing
t h e test button.
Notes:
1 The person carrying out t h e testing should decide which of the above tests are appropriate
by using their experience and knowledge of t h e installation being inspected and tested and
by consulting any available records (see Section 3.8.3 of this Guidance Note).
2
3
4
5
6
7
Where sampling is applied, t h e percentage u s e d is at t h e discretion of t h e inspector
(see Section 3.8.3 of this Guidance Note). A percentage of less t h a n 1 0 7o, or sampling
i n installations w i t h a sample population of less than 1 0 0 items of electrical equipment,
is inadvisable.
T h e tests n e e d n o t b e carried o u t i n t h e order s h o w n i n t h e table.
T h e EFLI test m a y b e used to confirm t h e continuity o f protective conductors at
socket-outlets and, w h e r e it is safe to d o so, at accessible exposed-conductive-parts of
current-using e q u i p m e n t a n d accessories.
Generally, accessibility m a y b e considered t o b e within 3 m f r o m t h e floor or f r o m
w h e r e a person can stand.
Where t h e circuit includes SPDs or other electronic devices that require a connection
to earth for functional purposes, these devices will require disconnecting t o avoid
influencing t h e test result and t o prevent t h e m being damaged.
Where an installation is fully loaded and the conductors are at their normal operating
temperatures, measured loop impedance values can b e directly compared with the
maximum values of EFLI set out in the tables in Chapter 41 of the Regulations. Loop
impedance data for unloaded conductors at 20 °C can b e found in t h e lET's On-Site Guide.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
129
3
8
Except at the origin of t h e installation, EFLI may b e determined by means other than
measurement (see Section 2.6.15).
9
See Section 2.6.24 w h e r e EFLI i s t o b e determined in installations with inverter supplies,
such as PEIs.
1 0 In some installations, it i s not always practicable to isolate the supply to certain parts of
the installation for t h e purposes of frequent periodic inspection a n d testing, for example
those supplying safety services. In these circumstances, s o m e information regarding t h e
state of insulation may b e obtained using a leakage current clamp meter (sometimes
called 'tong tester') - see Appendix C .
3.10.3 Additional notes on periodic testing
T h i s s e c t i o n p r o v i d e s s o m e n o t e s o n t h e practicalities o f c a r r y i n g out t h e p e r i o d i c t e s t s ,
p a r t i c u l a r l y w i t h i n a n i n s t a l l a t i o n w h e r e o n l y p a r t i a l i s o l a t i o n is p r a c t i c a b l e .
a
Continuity of protective earthing and bonding conductors, and
EFLItesting
If a n e l e c t r i c a l i n s t a l l a t i o n i s i s o l a t e d f r o m t h e supply,
it i s p e r m i s s i b l e to d i s c o n n e c t
p r o t e c t i v e e a r t h i n g a n d b o n d i n g c o n d u c t o r s f r o m t h e m a i n e a r t h i n g t e r m i n a l (MET)
in
o r d e r to v e r i f y t h e i r c o n t i n u i t y .
W h e r e it i s not p r a c t i c a b l e t o i s o l a t e a n e l e c t r i c a l i n s t a l l a t i o n f r o m t h e s u p p l y a t t h e
t i m e of t h e i n s p e c t i o n a n d t e s t i n g w o r k s , t h e p r o t e c t i v e e a r t h i n g o r b o n d i n g c o n d u c t o r s
s h o u l d not b e d i s c o n n e c t e d as, u n d e r f a u l t c o n d i t i o n s , t h e e x p o s e d - c o n d u c t i v e - p a r t s
a n d e x t r a n e o u s - c o n d u c t i v e - p a r t s c o u l d b e r a i s e d to a d a n g e r o u s v o l t a g e relative
to
Earth potential. In addition, the measurement
of EFLI at various parts of the installation is, for
practical reasons, carried out with the protective
earthing a n d bonding conductors connected.
A convenient
way to carry o u t t h e a b o v e p e r i o d i c tests i n a large installation c o u l d b e
to u s e t h e w a n d e r i n g l e a d m e t h o d t o test c o n t i n u i t y (see S e c t i o n 2.6.5,
2), n o t i n g t h a t t h e c o n d u c t o r s were
n o t d i s c o n n e c t e d f o r t h e s e tests,
test m e t h o d
a n d to d i r e c t l y
m e a s u r e EFLI a t t h e s a m e t i m e . W i t h t h e e a r t h i n g a n d b o n d i n g c o n d u c t o r s c o n n e c t e d ,
t h e tests c o n f i r m c o n n e c t i o n , b u t not t h e c o n t i n u i t y of t h e c o n d u c t o r s i n v o l v e d .
Motor circuits
L o o p i m p e d a n c e tests o n m o t o r circuits c a n o n l y b e c a r r i e d o u t o n t h e s u p p l y s i d e of
isolated m o t o r controlgear. A continuity t e s t b e t w e e n t h e circuit protective c o n d u c t o r
(cpc) a n d the m o t o r i s t h e n n e c e s s a r y .
b
Insulation resistance
I n s u l a t i o n r e s i s t a n c e tests
s h o u l d b e m a d e o n electrically isolated circuits w i t h a n y
e l e c t r o n i c e q u i p m e n t t h a t might
b e d a m a g e d by a p p l i c a t i o n of t h e test
voltage
disconnected, o r o n l y a m e a s u r e m e n t t o protective earth m a d e , w i t h t h e live conductors
c o n n e c t e d together.
It i s a d v i s e d to
d i s c o n n e c t f u n c t i o n a l e a r t h c o n n e c t i o n s to
r e s i d u a l c u r r e n t d e v i c e s (RCDs) a n d r e s i d u a l c u r r e n t circuit-breakers (with
protection)
(RCBOs) w h e n c a r r y i n g o u t i n s u l a t i o n r e s i s t a n c e tests,
overcurrent
as it m a y o t h e r w i s e
i n f l u e n c e t h e results.
643.3
For m o s t installations, t h e m o s t p r a c t i c a l test i s a n i n s u l a t i o n r e s i s t a n c e test b e t w e e n
live c o n d u c t o r s (connected
together)
a n d e a r t h ; i n p r a c t i c e , t i m e d o e s not u s u a l l y
a l l o w f o r a line to n e u t r a l t e s t . W h e r e e q u i p m e n t i s i n s t a l l e d t h a t m a y b e s u s c e p t i b l e
to d a m a g e by a 5 0 0 V DC t e s t voltage,
devices,
R e g u l a t i o n 6 4 3 . 3 states t h a t t h e t e s t s h o u l d b e c o n d u c t e d w i t h a t e s t v o l t a g e
of 2 5 0 V DC.
130
s u c h as e l e c t r o n i c c o n t r o l a n d m o n i t o r i n g
Guidance Note 3: Inspection & T esting
© The Institution of Engineering and Technology
3
Test
Recommendations
Continuity of
ring final circuit
conductors
Where there are records of previous tests, this test may not b e
necessary unless there m a y have been changes m a d e to the ring final
circuit
Polarity
At the following positions:
(a)
(b)
(c)
(d)
(e)
origin o f t h e installation
distribution boards
accessible socket-outlets
extremity of radial circuits
lighting circuits
Where there are records of previous tests, this test m a y not b e
necessary unless there may have b e e n changes to t h e circuit
EFLI
At t h e following
(a)
(b)
(c)
(d)
positions:
origin of t h e installation
distribution boards
accessible socket-outlets
extremity o f radial circuits
Insulation resist
ance
If tests are to b e m a d e :
Earth electrode
resistance
If tests are to b e m a d e :
(a)
(a)
between live conductors (connected together, where
applicable) and Earth at m a i n a n d final distribution boards
(note 6)
test each earth electrode or group of electrodes separately,
with t h e test links removed, a n d w i t h t h e installation
isolated f r o m the supply source
Functional tests
RCDs
Tests as required by Regulation
integral test button
643.1, followed
by operation
of the
Functional tests of
circuit- breakers,
isolators a n d
switching devices
and other functional
tests where
necessary
Manual operation to confirm that t h e devices disconnect t h e supply,
including functional test of AFDDsthat have a test button, by pressing
the test button.
Notes:
1 The person carrying out the testing should decide which of the above tests are appropriate
2
3
4
5
6
7
by using their experience and knowledge of t h e installation being inspected and tested and
by consulting any available records (see Section 3.8.3 of this Guidance Note).
Where sampling is applied, t h e percentage used is at t h e discretion of t h e inspector
(see Section 3.8.3 of this Guidance Note). A percentage of less than 10 7o, or sampling
in installations w i t h a sample population of less than 1 0 0 items of electrical equipment,
is inadvisable.
The tests n e e d n o t b e carried o u t i n t h e order s h o w n i n t h e table.
The EFLI test m a y b e used t o c o n f i r m t h e continuity of protective conductors at
socket-outlets and, where i t is safe t o d o so, at accessible exposed-conductive-parts o f
current-using e q u i p m e n t a n d accessories.
Generally, accessibility m a y b e considered to b e within 3 m f r o m t h e floor o r f r o m
w h e r e a person can stand.
Where t h e circuit includes SPDs o r other electronic devices that require a connection
to earth for functional purposes, these devices will require disconnecting t o avoid
influencing t h e test result a n d to prevent t h e m b e i n g damaged.
Where an installation is fully loaded and t h e conductors are at their normal operating
temperatures, measured loop impedance values can b e directly compared with t h e
maximum values of EFLI set out in t h e tables in Chapter 41 of the Regulations. Loop
impedance data for unloaded conductors at 20 °C can b e found in the lET's On-Site Guide.
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8
Except at the origin of the installation, EFLI may be determined by means other than
measurement (see Section 2.6.15).
9 See Section 2.6.24 where EFLI is to be determined in installations with inverter supplies,
such as PEIs.
1 0 In some installations, it is not always practicable to isolate the supply to certain parts of
the installation for the purposes of frequent periodic inspection and testing, for example
those supplying safety services. In these circumstances, some information regarding the
state of insulation may be obtained using a leakage current clamp meter (sometimes
called 'tong tester') - see Appendix C.
3.10.3 Additional notes on periodic testing
This section provides s o m e notes o n t h e practicalities of carrying o u t the periodic tests,
particularly within an installation where only partial isolation is practicable.
a
Continuity of protective earthing and bonding conductors, and
EFLItesting
If an electrical installation is isolated from t h e supply, it is permissible to disconnect
protective earthing and bonding conductors from the main earthing terminal (MET) in
order to verify their continuity.
Where it is not practicable to isolate an electrical installation from t h e supply at t h e
t i m e of the inspection and testing works, t h e protective earthing or bonding conductors
should not b e disconnected as, under fault conditions, t h e exposed-conductive-parts
and extraneous-conductive-parts could b e raised to a dangerous voltage relative to
Earth potential. In addition, the measurement of EFLI at various parts of the installation is, for
practical reasons, carried out with the protective earthing and bonding conductors connected.
A convenient way to carry o u t t h e above periodic tests i n a large installation could b e
to use the wandering lead m e t h o d to test continuity (see Section 2.6.5, test method
2), noting that t h e conductors were not disconnected for these tests, and to directly
measure EFLI at t h e same time. With t h e earthing and bonding conductors connected,
t h e tests confirm connection, but not t h e continuity of the conductors involved.
Motor circuits
Loop impedance tests o n motor circuits can only b e carried o u t o n the supply side of
isolated motor controlgear. A continuity test between t h e circuit protective conductor
(cpc) and the motor is t h e n necessary.
b
Insulation resistance
Insulation resistance tests should b e m a d e o n electrically isolated circuits with any
electronic
equipment
that might
b e damaged by application of the test voltage
disconnected, or only a measurementto protective earth made, with t h e live conductors
connected together.
It is advised to disconnect functional earth connections to
residual current devices (RCDs) and residual current circuit-breakers (with overcurrent
protection)
(RCBOs) w h e n carrying out insulation resistance tests, as it may otherwise
influence t h e results.
643.3
For most installations, t h e most practical test is an insulation resistance test between
live conductors (connected together) and earth; i n practice, t i m e does not usually
allow for a line to neutral test. Where equipment is installed that may be susceptible
to damage by a 5 0 0 V DC test voltage, such as electronic control and monitoring
devices, Regulation 643.3 states that t h e test should b e conducted with a test voltage
of 2 5 0 V DC.
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Check that information/warnings
are given at the distribution
board of circuits o r
equipment likely t o b e damaged by testing. Any diagram, chart or table should also
include this warning.
The results of insulation testing should b e compared with previous results, where
possible. Table 2.8 of this Guidance Note (Table 6 4 of BS7671) requires a minimum
insulation resistance of 1 M Q , but strictly speaking, this value applies only to initial
verification. It can, however, be used as a guide for periodic testing. Such low insulation
resistancereadingsmay indicate that there isa problem with an item of electrical equipment,
and where possible past records should be reviewed to identify historical readings to
determine if there has been a sudden, or gradual, decrease, from previous tests.
Where equipment
is disconnected
for these tests and the equipment
has exposed-
conductive-parts required by t h e Regulations to b e connected to protective conductors,
the insulation resistance between t h e exposed-conductive-parts and all live parts of the
equipment should b e measured separately and ought to comply with the requirements
of the appropriate British Standard for t h e equipment.
There is a range of possible outcomes when carrying out insulation testing. Tests are
typically made between all live conductors connected together and Earth at a test
voltage of 5 0 0 V DC.
The inspector will need to measure the values of insulation resistance for a given
distribution
board and then take a view based o n their engineering judgement as to
whether the results obtained are acceptable. It should b e noted that distribution boards
with large numbers of final circuits will generally give a lower insulation resistance value
than distribution boards with fewer final circuits.
c
Polarity
It should b e established whether there have been any additions or alterations to the
installation since its last inspection. If no additions or alterations have been made, the
polarity test may n o t b e necessary.
d
643.10
Operation of overcurrent circuit-breakers
Where protection against overcurrent is provided by circuit-breakers, the manual
operating mechanism of each circuit-breaker should b e operated to verify that t h e
device opens and closes satisfactorily.
It is n o t normally necessary or practicable to test the operation of the automatic
tripping mechanism
of circuit-breakers. A test would n e e d to b e made at a current
substantially exceeding t h e m i n i m u m tripping current in order to achieve operation
within a reasonable time. For circuit-breakers to BS EN 6 0 8 9 8 , a test current of not
less than two and a half times the rated tripping current of the device is needed for
operation within o n e minute, and m u c h larger test currents would b e necessary to
verify operation of the mechanism for instantaneous tripping.
If there is doubt about the integrity of the automatic mechanism for circuit-breakers of
t h e sealed type, designed n o t to b e maintained, it will normally b e m o r e practicable to
replace the device than to make further tests. Such doubt may arisefrom visual inspection,
if the device appears to have suffered damage or undue deterioration, or where there is
evidence that the device may have failed t o operate satisfactorily in service.
Circuit-breakers with the facility for injection testing may b e so tested and, if appropriate,
their relay settings confirmed.
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3
e
Operation of devices for isolation and switching
Where means are provided i n accordance with t h e requirements of t h e Regulations
for isolation and switching, the devices should b e operated to verify their effectiveness
and checked to ensure adequate and correct labelling.
It should b e verified by inspection that easy access to such devices is maintained and
that effective operation is not impaired by any material placed near the device. Access
and operation areas may b e required to b e marked to ensure they are kept clear.
For isolating devices in which the position of the contacts o r other means of isolation is
externally visible, visual inspection of operation is sufficient and n o testing is required.
The operation of every safety switching device should b e checked by operating t h e
device in t h e manner normally intended, t o confirm that it performs its function
correctly in accordance with t h e requirements of BS 7671.
Where it is a requirement
that the device interrupts all t h e supply conductors,
the
use of a proprietary test lamp, or two-pole voltage detector connected between each
line and t h e neutral on the load side of the switching device, is essential to confirm
isolation. Reliance should not b e placed o n a simple observation that the equipment
controlled has ceased to operate.
Where switching devices are provided with detachable or lockable handles in accordance
with the Regulations, a check should b e made to verify that the handles or keys are n o t
interchangeable with any others available within the premises.
643.10
Where any f o r m of interlocking is provided, such as between a main circuit-breaker
and a n outgoing switch or isolation device, the integrity of t h e interlocking must b e
verified; this may b e beyond the scope of the inspector and something that is referred
to a manufacturer or specialist.
Where switching devices are provided for isolation or for mechanical
maintenance
switching, the integrity of the means provided to prevent any equipment
from being
unintentionally or inadvertently energized or reactivated m u s t b e verified.
f
643.7
Operation of RCDs
Fault protection
Where an RCD is provided for fault protection, t h e operating time should generally b e
n o greater than those stated in Table 41.1 (Regulation 411.4.5) for final circuits and 5 s
for distribution circuits, unless supplementary bonding has been applied in accordance
with Regulation 419.3.
Additional protection
643.8
Where an RCD with a rated residual operating current n o t exceeding 3 0 m A is used t o
provide additional protection in t h e event of failure of basic protection and/or failure of
t h e provision for fault protection or carelessness by users, t h e effectiveness is d e e m e d
to have b e e n verified where an RCD meeting t h e requirements of Regulation 415.1.1
disconnects within 3 0 0 ms w h e n tested at a current equal to or higher than its rated
residual operating current (lAn).
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3.11 Electrical Installation
653 J
Condition Report (EICR)
A m o d e l of the EICR is provided in Appendix 6 of BS 7671, together with a m o d e l
Condition Report Inspection Schedule, and Schedules of Circuit Details and Test
Results. Typical completed forms are given in Section 5 of this Guidance Note.
The full EICR documentation
Electrical
Installation
comprises the following:
Condition
Report
(EICR)
and
Condition
Report Inspection
Schedule (one or more)
and
Schedule
On completion
of Circuit
Details
and Schedule
of periodic inspection
of Test Results
(one or more)
and testing, the EICR and its accompanying
schedules must b e given to the client or person who ordered the inspection.
A very important point to remember is that any damage, deterioration, defects,
dangerous conditions and non-compliance with B S 7 6 7 1 that may give rise to danger
(’danger' being a risk of injury to persons or livestock) must b e recorded o n the Report.
Classification codes C l to C3 indicate danger and non-compliances
with BS 7671;
these are explained in Table 3.5.
Each separate item entered in the Section K 'Observations'
section of t h e Report
should b e coded C l , C 2 or C3 as appropriate, or, exceptionally, Fl (see Table 3.5). Only
one classification code is to b e recorded against each observation.
Where an installation defect or non-compliance with the Regulations has attracted a
code of C l , C 2 or Fl, t h e overall assessment of the Report must b e 'unsatisfactory'.
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▼ Table 3 . 5 Classification of danger a n d non-compliances (for use during periodic
inspection a n d testing)
Classification of
danger or
non-compliance
Description
Notes and guidance
Cl
Danger present. Risk of
injury. Immediate
remedial action
required.
To b e attributed to matters that cannot b e
left. It is suggested that these are rectified or
possibly, that isolation m a y be recommended
or necessary. Examples include accessible
bare live parts, badly damaged equipment
with risk of access to live parts, incorrect
polarity, a n d / o r arcing or burning f o u n d in
switchgear.
C2
Potentially dangerous:
urgent remedial action
required.
T o b e attributed to issues that, while urgent,
do not require immediate remedial action.
Examples include a non-earthed
installation (this requires a further fault to
result i n danger), fundamentally undersized
cables, EFLI values greater t h a n required by
BS7671, a 'borrowed1 neutral, equipment
with inappropriately selected IP (this m a y
warrant C 1 if severe), insulation readings
under 1 MQ, a n d connections not housed
within appropriate enclosures.
134
C3
Improvement
recommended.
To b e attributed where C l or C2 do n o t apply.
Examples include t h e absence of most
warning notices, absence of t h e required
diagrams a n d charts, n o or incorrect marking
of conductors at terminations, a n d absence
of an RCD specified for additional protection
(where t h e circuit otherwise tests as normal).
Fl
Further investigation
required without delay.
To be attributed where the inspection has
revealed an apparent deficiency that could
not, due to the limitations or extent of the
inspection, be fully identified and where
further investigation m a y reveal a C I or C 2
item. An example could b e where
characteristics of electricity supply (such as
voltage or external EFLI) do not conform to
supply industry norms. May also be used
where part of an installation included i n the
scope of the inspection a n d test could not b e
accessed.
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3.12 Periodic inspection of installations constructed
to an earlier edition of BS7671 or the lEEWiring
Regulations
People often ask what standard should b e applied w h e n carrying o u t t h e periodic
inspection
of a n installation
constructed
in accordance with an earlier edition
of
BS 7671, or an even earlier edition of t h e lEEWiring Regulations, or to an unknown
standard. Each edition of the Wiring Regulations has provided for an increase in
safety to the users of installations. Some installation practices and methods that were
compliant with earlier editions would n o w b e considered unacceptable or dangerous,
such as the use o f a public water pipe as a means of earthing.
In all cases, t h e inspection should b e carried o u t against the current edition of BS7671 .
It is likely that there will b e items that d o not comply with that edition, but this does
n o t necessarily m e a n that t h e installation is unsafe. If the inspector considers that an
item, although not warranting code C l or C2, requires improvement, it should b e given
code C3 o n the EICR. If the item does not require improvement,
it may b e recorded
as an observation but it does not warrant a classification code.
Reference is made to existing installations both in the second paragraph of the
Introductions to BS 7 6 7 1 and its amendments, and in the Note by the HSEthat follows
the Preface to BS 7671.
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NOTES
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Test instruments and 4
equipment
4.1
Instrument standard
BS EN 61010 Safety requirements
for electrical equipment
for measurement,
control,
and laboratory use is the basic safety standard for electrical test instruments.
The series of standards to which electrical test equipment
for verification of measures
for protection against electric shock is BS EN 61557 Electrical safety in low voltage
distribution systems up to 1000 1/ a.c. and 1500 1/ d.c. Equipment for testing,
measuring or monitoring of protective measures. This standard includes performance
requirements
and requires compliance with BS EN 61010.
In Section 1.1 of this Guidance Note, reference was made to the use of test leads
conforming
to HSEGS38. The HSE always advise only to carry out live tests that are
actually useful and informative, so as to minimize danger; the inspector should always
consider whether any particular live test is necessary before undertaking it. The safety
measures and procedures set o u t in GS38 should b e observed for all instruments,
leads, probes
and accessories. Some test instrument
their instruments
are used in conjunction
manufacturers advise that
with fused test leads a n d probes. Other
manufacturers advise the use of non-fused leads and probes where t h e instrument
has in-built electrical protection, but it should b e noted that such electrical protection
does not extend to the probes and leads.
Appendix 14 of BS7671 also recommends
"the measurement
that:
should always b e made on t h e output terminals of a suitably
rated protective device. If such a device is not present then a temporary one should
b e fitted. Measurement
should never b e made where overcurrent protection is not
present between the point of connection and the supply transformer. Fused test
leads alone do not meet this requirement."
Where unsure, a risk assessment should b e carried out to establish if fused test leads
should b e used.
Manufacturers may provide multifunction test instruments to BS EN 61557-10 that
combine more than one, or all, of the functions listed in Sections 4.3 to 4.8. Some of
these instruments may have additional features such as current measurement (via clamp).
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4.2
Instrument
accuracy
The accuracy of a n e w or repaired instrument should b e established to provide a point
of reference. Accuracy is usually confirmed
by calibration, but a calibration certificate
may not b e supplied with the instrument
unless specifically requested. A certificate
of conformity
may b e provided indicating that the instrument's
as part of the manufacturing
accuracy was verified
process. Such verification follows the same procedure as
calibration, but individual calibration data is n o t issued.
A basic measurement accuracy of 5 7 o i s usually adequate. In the case of analogue
instruments, a basic accuracy of 2 7 o o f full-scale deflection will provide the required
accuracy measurement
over a useful proportion
of the scale.
It should not b e assumed that the accuracy of the reading taken in normal field use
will b e as good as the basic accuracy. The ’operating accuracy’ is always worse than
the basic accuracy, and additional errors derive from three sources:
( a ) instrument
e r r o r s : basic instrument accuracy applies only in ideal conditions.
The actual reading accuracy can also b e affected by:
(i)
digital instruments.
Sources of error: test leads, fused leads, battery condition, ambient temperature,
electrical noise, etc.
(ii)
analogue instruments.
Sources of error: Orientation
of the instrument
on older instruments'.
With
hand-cranked units, cranking speed, can also affect performance.
(b) l o s s o f calibration:
manufacturer's
instruments should b e periodically calibrated following
recommendations
and
procedures
traceable
to
National
Standards. Intermediate checks can be made to ensure there are n o major errors in
measurement by comparing readings with those obtained from other instruments,
or by the use of a proprietary 'check box' having clearly defined characteristics.
In all cases, the t y p e and frequency of recalibration or checking required should b e as
specified by the instrument manufacturer. However, the user should take into account
ambient environmental and usage factors, as appropriate. For example, if an instrument
is left in storage at a constant temperature in a dry environment for long periods, a n d /
or is used infrequently, t h e user may b e able to extend the recalibration interval.
However, if an instrument is roughly handled and is regularly transported a n d stored in
vehicles (and hence is subjected to fluctuations
in temperature
and humidity caused
by changes in time of day/night and time of year), then more frequent confirmation
of
accuracy would b e appropriate.
Instruments should also b e subjected t o regular checks before use so that errors
caused by deterioration of leads, probes, connectors, etc. d o n o t result in inaccurate
readings being recorded when, for example, Schedules of Test Results are compiled.
Typically, in analogue instruments,
this corresponds to making measurements
near to the zero point on the scale, where inaccuracies and non-repeatability
at all evident with this type of electromechanical
very
are not
movement.
It is essential t h a t an i n s t r u m e n t is inspected f o r damage a n d that the s a f e t y
a n d the accuracy o f a n instrument
is c o n f i r m e d a f t e r any incidences o f
mechanical or electrical mishandling.
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(c) field errors: t h e instrument reading accuracy will also b e affected by external
influences as a result of working in the field environment.
These influences can
take many forms. Some sources of inaccuracy are described in the appropriate
sections of this Guidance Note.
BS EN 61557 requires a maximum operating error of n o m o r e than ± 3 0 7 o o f reading
over the stated measurement range, taking into account the worst-case environmental,
supply and battery conditions.
To achieve satisfactory in-service performance, it is essential to b e fully informed about
the test equipment,
how it is to b e used, and the accuracy to b e expected.
Traceability to National Standards can b e assured by using a calibration laboratory
accredited by a National Accreditation Body. In the UK this is t h e United Kingdom
Accreditation Service (UKAS). A list of accredited laboratories can b e found at
www.ukas.com or a search for sources of calibration by instrument can b e made at
https://www.ukas.eom/find-an-organisation/browse-by-category/#orgtype-273.
4.3
643.2.1
Low-resistance ohmmeters
The continuity of conductors and connections to exposed-conductive-parts
and
extraneous-conductive parts, if any, shall be verified by a measurement of resistance on:
(a) protective conductors, including protective bonding conductors; and
(b) in the case of ring final circuits, live conductors.
The instrument used for low-resistance tests may b e either a specialized low-resistance
ohmmeter or t h e continuity range of an insulation and continuity tester. The test current
may b e DC or AC. It is recommended that it b e derived f r o m a source with no-load
voltage between 4 V and 24 V and a short-circuit current of not less than 200 m A .
The measuring range should cover the span 0.2 Q to 2 Q , with a resolution of at least
0.01 Q for digital instruments.
Instruments conforming to B S E N 61557-4 will meet the above requirements.
Field effects contributing to in-service errors include probe or crock-clip contact
resistance, test lead resistance, AC interference and thermocouple effects in mixed
metal systems.
Whilst contact resistance cannot b e eliminated with two-terminal testers, and can
introduce errors, the effects of lead resistance can b e eliminated by measuring this
prior to a test and subtracting t h e resistance f r o m t h e final value, or by using t h e test
instrument's
'nulling' feature built in to most m o d e r n instruments.
an external AC source (interference
pick-up) cannot b e eliminated,
Interference from
although it may
b e indicated by vibration of the pointer of an analogue instrument or by an unstable
digital readout. Thermocouple effects can b e eliminated by reversing the test probes
and averaging the resistance readings taken in each direction.
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4.4
Insulation resistance testers
The instrument used should b e capable of developing the test voltage required across
the load.
The test voltage required is:
Table 64
(a) 2 5 0 V DC for SELVand PELV circuits with equipment such as SPDs that may
influence test results or b e damaged - but the insulation resistance is to b e at
least 1 M Q (643.3.2);
(b) 5 0 0 V DC for all circuits rated u p to and including 5 0 0 V, except SELVand PELV
circuits; and
(c) 1,000 V DC for circuits rated above 5 0 0 V and u p to 1,000 V.
Instruments conforming to BSEN 61557-2 will fulfil all the above instrument requirements.
When an insulation resistance test is applied to a test subject, the measurement
may
b e influenced by different circuit characteristics, for example:
(a) capacitive charging;
(b) absorption or polarization of the insulation; and
(c) conduction or leakage currents.
These factors can b e reduced or eliminated
by extending the test time for which
the test voltage is applied, and can be seen as a steady insulation reading on the
instrument, after a n initial rapid increase in value.
Capacitance may b e as high as 5 pF and the instrument should have an automatic
discharge facility capable of safely discharging such a capacitance. Following an
insulation resistance test, t h e instrument should b e left connected until t h e capacitance
within the installation has b e e n fully discharged.
4.5
EFLI testers
Loop impedance testing is the practice of measuring the impedance of a live circuit.
Typically, t h e circuit voltage, either line-neutral (L-N), line-Earth (L-E) or line-line (L-L),
is first measured to acquire the off-load voltage. A load is then applied and t h e n e w
circuit voltage is measured. The voltage drop is used to calculate the impedance of the
circuit. Exactly how this is done differs between manufacturers. However, all methods
can b e presented with electrical conditions that pose a challenge to the measurement.
Sources of error can include:
(a) electrical noise and transients;
(b) external load switching;
(c) harmonics;
(d) ROD uplift;
(e) test lead contact resistance; and
(f) instrument resolution and proximity to the source transformer (instrument
resolution for many instruments means the instrument cannot provide adequate
readings if taken too close to a supply transformer).
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Three t y p e s of measurement
a r e t y p i c a l l y available, l i s t e d i n o r d e r of preference:
(a) t w o - w i r e high current test;
(b) t h r e e - w i r e non-trip test; a n d
(c) t w o - w i r e n o n - t r i p t e s t .
Two-wire high current test:
This is the test that should
the circuit.
a l w a y s be employed
The l o a d u s e d u s u a l l y generates
unless there
between
is a n R C D o r R C B O i n
2 A a n d 1 5 A. This is s u f f i c i e n t to
c r e a t e a m e a s u r a b l e v o l t a g e d r o p a n d c o n s e q u e n t l y a s t a b l e a n d a c c u r a t e result. T h e
t e s t u s u a l l y lasts f o r n o m o r e t h a n 3 - 4
m o r e t h a n 4 0 ms o n two consecutive
s i n total, w i t h t h e l o a d b e i n g p r e s e n t f o r n o
half-cycles.
Test currents higher than 15 A risk tripping some low current miniature circuit-breakers (MCBs).
Three-wire non-trip test:
W h e r e t h e r e a r e RCDs o r R C B O s present,
out using a non-trip
not to trip
the
significant
voltage
l o o p impedance
RCD, typically
drop.
t h e L-E f a u l t l o o p i m p e d a n c e m a y b e c a r r i e d
test. The l o a d current
a r o u n d 1 5 m A . However,
Consequently,
in this test is s m a l l enough
1 5 m A does
not
create
a
many m o r e test cycles a r e p e r f o r m e d a n d the
t e s t r u n s f o r significantly longer, w i t h t h e r e s u l t s far m o r e s u s c e p t i b l e to v a r i a t i o n .
Two-wire non-trip test:
The third o p t i o n o n s o m e instruments
of not r e q u i r i n g the third
lighting
i s a t w o - w i r e non-trip
test lead to b e connected,
test. This h a s t h e advantage
a n d i s especially
u s e f u l on some
circuits.
T h e d r a w b a c k is that it is t h e most t e c h n i c a l l y difficult
susceptible
to m o r e errors than the three-wire
test f o r t h e i n s t r u m e n t a n d c a n b e
test. It should only b e used a s a last resort.
Safety
To m i n i m i z e e l e c t r i c s h o c k h a z a r d f r o m t h e p o t e n t i a l o f t h e p r o t e c t i v e c o n d u c t o r
d u r i n g L-E i m p e d a n c e tests,
t h e test
d u r a t i o n s h o u l d b e w i t h i n safe l i m i t s . For
two-wire
high current
tests, the instrument
or a time
determined
by the s a f e t y limits
B S I E C 60479-1
i f t h e voltage
Effects
of current
should
derived
on human
cut off the test current
f r o m the information
beings
and
livestock.
after
40 ms
contained
General
within
aspects,
rise o f t h e p r o t e c t i v e c o n d u c t o r e x c e e d s 5 0 V d u r i n g the t e s t . O n s o m e
installations, t h i s t h r e s h o l d m a y b e 2 5 V , e s p e c i a l l y w h e r e l i v e s t o c k a r e p r e s e n t .
For low current
disconnect
(non-trip)
tests, the instrument
the test if the e a r t h voltage
must
monitor
the e a r t h voltage
and
is exceeded.
Sources o f error
T h e l o w e r t h e l o a d c u r r e n t e m p l o y e d i n t h e test, t h e m o r e v a r i a t i o n a n d e r r o r i s likely
i n t h e result,
supply
as t h e voltage
drop
i s p r o p o r t i o n a l l y lower.
will a l s o c o m p r o m i s e accuracy a n d repeatability,
differentiate
between
a voltage
drop
created
i n d u c e d by n o i s e o r h a r m o n i c s , etc. For this
D i s t o r t i o n o r n o i s e o n the
a s the instrument
by the applied
c a n n o t easily
l o a d o r a voltage
r e a s o n , the test
with
change
t h e higher
load
currents should always b e u s e d w h e r e possible.
G u i d a n c e Note
© T h e Institution
3: Inspection
& Testing
of Engineering a n d Technology
141
4
Repeating a test is advised if there is concern about t h e validity of the result, especially
o n noisy supplies.
RCD u p l i f t
RCD uplift is a phenomenon frequently encountered when performing a two- or three-wire
non-trip test. During the test, the RCD internal impedance may sometimes be measured,
increasing the overall circuit impedance. This may be as high as 0.5 Q or more.
RCD uplift can b e avoided by choosing an instrument that declares immunity to this
effect. Alternatively, if uplift is suspected, measuring o n the source and load sides
of the RCD will identify any additional impedance
within the RCD. This can then be
deleted f r o m the measurement.
This phenomenon
is not encountered
with high test currents, but these tests will trip
the RCD during the test, preventing their use.
Transformer impedances can also affect results, as the impedance close to source can
b e very reactive, rather than resistive. This is only a real issue when measuring close
to the source transformer, but the instrument
significant in this location.
resolution and accuracy becomes very
Test l e a d errors
Test leads can induce errors from:
(a) internal lead resistance;
(b) contact resistance of the probes or clips; and
(c) internal fusing of t h e test leads.
As with t h e low resistance ohmmeter
section earlier, t h e test lead resistance can b e
’nulled' or may already b e accounted for in the instrument. If not, the lead resistance
should b e measured and deducted f r o m future measurement values.
Contact resistance can add significantly to t h e circuit impedance.
Inspectors should
ensure that probes are sharp and that clips grip tightly.
Fused leads can add significantly to lead resistance. A 5 0 0 mA fuse can add as much
as 1.8 Q in a test lead pair. If fused leads are used for loop impedance testing, they
will need to b e fused with higher rating fuses, typically 7 A or 10 A fuses, t o prevent
the test current rupturing the fuse.
Leads compliant to HSE GS38 should be adequate.
Instrument
accuracy and resolution
The resolution of a n instrument is the smallest increment that the instrument can
detect and display. This is usually measured in terms of the multiples of the least
significant
(right-most)
digit of t h e instrument
display. Instrument
resolution
can
compromise measurement accuracy, especially at the lower loop impedances found
near t h e source transformer. When measuring loop impedances below 0.1 Q, caution
should b e exercised in the interpretation
significantly affects measurement
142
Guidance
N o t e 3: Inspection
© T h e Institution
& Testing
of Engineering a n d Technology
of the results, as the instrument accuracy
values close to t h e lowest end of the range.
For example, when attempting to measure a l o o p impedance of 0.03 Q , an instrument
that declares a ± 5 °/o±3 digits o n a digital display could give an answer between zero
and 0.06 Q and b e within its declared accuracy.
Instruments conforming to BS EN 61557-3 will fulfil the above requirements under
m o s t situations.
These instruments
may also offer additional facilities for deriving prospective
fault
current. The basic measuring principle is the same as for EFLI testers. The current
is calculated by dividing the loop impedance
Instrument accuracy is determined
instrument
value into the nominal mains voltage.
by the same factors as for EFLI testers. In this case,
accuracy decreases as scale reading increases, because the loop value is
divided into the mains voltage. It is important to note these aspects and to consult the
manufacturer's documentation.
4.6
Earth electrode resistance testers
There are three general methods referred to in Section 2 of this Guidance Note:
(a) test method
E l , using a dedicated
earth electrode
tester (fall of potential,
three- or four-terminal type);
(b) test m e t h o d E2, using a dedicated earth electrode tester
(stakeless o r
clamp-type); and
(c) test m e t h o d E3, using an EFLItester.
The most accurate of these is test method E l .
Test method
E2 is more accurate if there are a number
of earth electrodes.
The
method the stakeless or probe tester cannot b e used to measure the resistance of a
single earth electrode unless there is at least one other earth electrode connected,
which may b e formed from extraneous-conductive-parts or, in TN systems, the means
of earthing of the supply.
4.7
RCD testers
The trip times of RCDs are required to b e verified, to ensure adequate disconnection
under fault conditions.
RCDs are tested by applying a test load to t h e RCD, inducing a calibrated test current
to flow in t h e L-E circuit. This creates a n imbalance in t h e L-N currents in t h e RCD and
the device trips. The t i m e it takes to trip is then displayed.
The test instrument should b e capable of applying the full range of test current to an
in-service accuracy as given in BS EN 61557-6. This in-service reading accuracy will
include the effects of voltage variations around the nominal voltage of the tester.
The range of RCD operating currents supported is generally limited to between
10 m A
and 1 A; exceeding these limits presents severe design and cost implications
to the
instrument design.
As with loop impedance testing, the Earth voltage is monitored and prevented f r o m
exceeding the touch voltage limit, either 5 0 V or 2 5 V, depending o n t h e requirements
of t h e location.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineeringand Technology
143
4
RCDs a r e u s u a l l y tested
to ensure:
(a) t h e y d o n o t t r i p w i t h f a u l t c u r r e n t s less t h a n 5 0 7o o f t h e i r o p e r a t i o n a l rating.
(b) they trip in the required time at fault current of 100 7o of their operational rating.
(c) In addition to t r i p time testing, i n s t r u m e n t s offer the ability to test the RCD's
t r i p p i n g c u r r e n t t h r e s h o l d . For t h i s test, a r a m p c u r r e n t i s a p p l i e d f r o m less t h a n
5 0 7 o o f t h e R C D r a t i n g t o 110 7 o . T h e c u r r e n t a t w h i c h t h e R C D t r i p s is t h e n displayed:
this identifies if the R C D i s overly sensitive and may cause nuisance tripping.
I n s t r u m e n t s c o n f o r m i n g t o B S E N 6 1 5 5 7 - 6 w i l l f u l f i l the a b o v e r e q u i r e m e n t s .
4.8
Phase rotation instruments
BS EN 6 1 5 5 7 - 7 gives t h e r e q u i r e m e n t s for m e a s u r i n g e q u i p m e n t for testing t h e p h a s e
s e q u e n c e i n t h r e e - p h a s e d i s t r i b u t i o n systems,
mechanical,
visual and/or
audible
w h e t h e r t h e i n d i c a t i o n is given
by
means.
BS E N 61557-7 includes requirements that:
(a) indication
system
shall b e unambiguous
voltage
o r within
between
8 5 7o a n d 110 7o of the
t h e range of t h e n o m i n a l voltage
a n d between
nominal
9 5 7o
a n d 1 0 5 7o o f t h e n o m i n a l s y s t e m f r e q u e n c y ;
(b) t h e m e a s u r i n g e q u i p m e n t s h o u l d b e s u i t a b l e f o r c o n t i n u o u s operation;
(c) the measuring equipment
should be s o designed that when either one o r two
measuring
l e a d s a r e c o n n e c t e d t o e a r t h a n d t h e r e m a i n i n g m e a s u r i n g lead(s)
r e m a i n c o n n e c t e d to their corresponding line conductors, t h e resulting total
current
(d) the
to e a r t h should
measuring
not exceed
equipment
should
3.5 m A rms;
not
be
damaged,
nor
should
the
user b e
e x p o s e d to danger i n situations w h e r e t h e m e a s u r i n g e q u i p m e n t is c o n n e c t e d
to
1 2 0 7o
voltage
of t h e rated system voltage o r to
1 2 0 7o
of its rated m a x i m u m
range; a n d
(e) portable measuring equipment
should be provided with permanently
attached leads
or with a plug device with live parts not accessible, whether plugged o r unplugged.
4.9
Thermographic equipment
A l t h o u g h t h e r m o g r a p h i c s u r v e y i n g e q u i p m e n t i s not
test instrument,
especially
notes
such
r e c o g n i z e d by B S 7 6 7 1 as a
e q u i p m e n t c a n b e i n v a l u a b l e i n assisting e l e c t r i c a l i n s p e c t i o n s ,
in the early identification
a r e t h e r e f o r e included
of possible
points
of overheating
h e r e o n this t y p e of equipment.
in circuits. S o m e
It must,
however,
be
r e m e m b e r e d that e q u i p m e n t m u s t b e operating a n d m u s t b e 'thermally transparent'
i n o r d e r f o r a t h e r m o g r a p h i c survey to b e a b l e to s e e t e m p e r a t u r e changes.
Important note: it is recommended that persons refer to the requirements
of the EAWR and the HSE's guidance in HSR25 prior t o undertaking any
work activity which places themselves or those under their control in close
proximity to live parts.
144
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
4
It is relatively easy to make arrangements to disconnect small installations, such as those
at domestic premises, f r o m the supply, to facilitate periodic inspection and testing.
However, asthe size and complexity of an installation increases, isolation f r o m the supply
becomes increasingly difficult. This is particularly true where continuity of supply has
health implications, as may b e the case in hospitals and similar premises, or financial
implications, as would b e the case in banks, share-dealing and commodities markets,
and t h e like. Nevertheless, i t remains necessary to confirm the continuing
of such installations
suitability
for use. Therefore, they must still b e subjected to planned and
preventative maintenance or regular periodic assessment of their condition.
It may well b e possible to carry o u t a thorough visual inspection of such installations
without subjecting the inspector or others in t h e building to any danger, and such an
inspection may identify many common
defects caused by use/abuse. Furthermore,
experience of such installations may provide a valuable insight into commonly occurring
cases of wear a n d tear.
Some defects, however, cannot b e discovered by visual inspection alone. For example,
incorrectly tightened connections can result in a high resistance joint, which can t h e n
cause a high temperature
to occur locally to t h e connection.
If left uncorrected
over
time, further deterioration of t h e connection may well occur, leading to a continuing
increase in temperature,
which may subsequently
present a risk of fire. This fire
risk will b e significantly increased in installations where a build-up
of dust or other
flammable materials can occur in close proximity to the source of heat. It should
also b e remembered
that increased heat at terminations
can result in accelerated
deterioration of the insulation locally. Heating effects symptomatic of a fault or other
problem
within an electrical installation
can also occur as a result of cyclical-load
operations, use of conductors of inadequate current-carrying capacity, incorrect load
balancing and more mechanically related issues, such as incorrect alignment of motor
drive couplings and overtightened belt-drives.
A number of manufacturers offer infrared imaging equipment
which can b e used to
identify such ’hot spots'. Infrared thermography works o n t h e principle that all materials
emit electromagnetic
radiation in the infrared region, which can b e detected
by a
thermal imaging camera.
The amount of radiated energy detected can b e presented in a readily usable form,
typically being shown as differences in colour that vary with the temperature being
detected. Figure 4.1 shows a colour/temperature correlation indicator such as those
that may accompany images. Such scales will aid the person ordering t h e inspection
or responsible for maintenance activities in their interpretation
of t h e thermal images.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
145
4
▼
Figure 4 . 1 A colour/
temperature correlation
indicator
In terms of visual inspection, t h e busbar connections in
Figure 4.2 appear to be satisfactory.
However, if the same connections are viewed using a
[
thermal imaging camera (Figure 4.3), it is evident that
t h e connections to t h e centre are running significantly
160.0 -
hotter than those to either side.
150.0140.0 -
This higher temperature may indicate a loose connection
130.0 -
or connections, but in this case is probably d u e to the
120.0 - |
centre bar carrying a significantly higher current than those
to either side of it. The person carrying out the inspection
110.0 - "
could suggest that their client looks into improving t h e
100.0 -■
load balancing of this part of the installation.
| <99.3°F 1
▼
Figure 4.2
Bolted connections at a
busbar as seen by the eye
In a further example, Figure 4.4 shows a contactor
with t h e thermal image highlighting a potential loose
termination. After this has been tightened,
Figure
4.5 shows the result, with all three terminations now
operating at a m u c h more uniform temperature.
Whilst such remedial work is being carried out, it is
sensible to inspect t h e insulation of t h e conductors i n
t h e terminations to confirm that the insulation remains
▼
Figure
effective and has not suffered significant damage.
4.3
Bolted connections at a
busbar viewed using
thermal imaging
The requirements of the EAWR m u s t b e taken into
account w h e n considering t h e use of thermographic
surveying equipment, as its use may necessitate t h e
temporary removal or bypassing of measures that
provide basic protection (as defined in BS 7671), such as
opening doors to electrical panels and/or t h e removal of
barriers and covers. The requirements of Regulation 14
of t h e EAWR (Work o n or near live conductors), which is
▼
F i g u r e 4 . 4 Thermal image
of contactor showing
termination on right is
too hot
2200-
reproduced as follows, are particularly pertinent:
"No person shall b e engaged in any work activity
on or so near any live conductor (other than one
suitably covered with insulating material so as t o
prevent danger) that danger may arise unless -
XBQfOOib
1SJ0-
(a) it is unreasonable
MOOt200-
in all the circumstances for it to
be dead; and
ttuo-
(b) it is reasonable in all the circumstances for him to
▼
F i g u r e 4 . 5 Thermal image
of contactor after loose
termination has been
tightened
0FL1R
220 C-if]
m-|J
MOO'
1200'
icoo-
146
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
be at work on or near it while it is live; and
(c) suitable
precautions
the provision
(including
o f suitable
are taken to prevent injury"
where
protective
necessary
equipment)
4
HSR25 recognizes that it may b e necessary, in some circumstances, for conductors to
remain live during testing or diagnostic work. However, such work in close proximity to
live conductors may only b e carried out if it can b e done safely and if all precautions
required to allow it to b e done so are put in place. Additionally, the work m a y only
b e performed by persons w h o are suitably competent with regard to the type and
nature of the work activity being performed, as required by Regulation 16 of the EAWR
(Persons to be competent
to prevent danger or injury). HSR25 also makes clear that
although live testing may b e justifiable, it does n o t follow that there will necessarily b e
justification for subsequent repair work to b e carried out live.
Persons carrying out thermographic surveying should:
(a) have sufficient competence to prevent danger and injury.
(b) understand
the system being worked on, t h e hazards that may arise as a result
of t h e work and t h e precautions that are required to prevent danger.
being inspected which are, or are
(c) b e able to identify those parts of equipment
capable of being, live when the supply to the equipment
is switched on.
(d) implement all precautions required to prevent injury that have been identified
as part of t h e risk assessment for the work.
(e) maintain the maximum
possible distance f r o m the live or potentially
described above at all times.
(f) maintain
effective control of the area in which the equipment
live parts
being inspected
is situated.
(g) ensure
that all protective measures that m a y have been affected by their
actions when carrying out t h e inspection
work are fully reinstated. All guards
and barriers must b e replaced and panel doors, lids and covers must b e closed
and secured properly after t h e inspection is completed.
As previously mentioned, thermographic inspection can b e an effective m e t h o d of
identifying potential defects that may not be identified by a more conventional visual
inspection. However, such thermal surveying should not b e seen as a substitute for
periodic inspection and testing, but rather as an additional tool that can b e used by
t h e inspector. Thermographic surveys can b e a highly effective means of targeting
preventative maintenance where it is m o s t required. Defects identified may b e factored
into the planned maintenance
programme
for t h e installation, or, where necessary,
may justify the remedial work being performed without delay.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
147
NOTES
148
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Forms
This section provides guidance on completing
the necessary schedules, certificates
and reports associated with inspection and testing. Sample certificates a n d report,
completed with typical entries, are provided, together with sample Schedules of
Inspection, Circuit Details and Test Results, again completed
The section also contains some notes on completion
with typical results.
of the forms, although helpful
information on this will also b e gained by reading earlier sections of this Guidance Note.
5.1
Initial verification (inspection and testing) forms
Following the initial verification of a new installation o r of an addition or alteration to
an existing installation, an Electrical Installation Certificate
(EIC) or Minor Electrical
Installation Works Certificate (MEIWC) is required to b e completed and issued, together
with inspection schedule(s) and test result schedule(s).
(a)
Form 1 : EIC (three-signatory
version from Appendix 6 of BS 7671).
When an EIC is used, appropriate numbers of t h e following
forms are required to
accompany the Certificate:
(b) Form 2: Schedule of Inspections for domestic and similar premises with u p to
100 A supply, or a more extensive schedule where necessary (see below).
(c) Form 3: generic Schedule of Test Results.
642.3
Form 2 is not suitable for the inspection of installations rated at more than 100 A
or that are more complex. For such installations, t h e inspector will probably need to
formulate their own inspection schedules. These should b e based o n the requirements
of Regulation 642.3 and t h e list of examples of items requiring inspection during initial
verification, given i n Appendix 6 of BS 7671.
For completeness,
two samples of typical completed
Form 3 s (Schedule of Circuit
Details and Test Results) are included here, one being for a single-phase installation
a n d the other for a three-phase installation.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineering and Technology
149
5
5.2
Minor works
The complete set of forms for initial verification (inspection
and testing) may not b e
necessary for minor works. When an addition to a n electrical installation does not
extend to the installation of a n e w circuit, t h e MEIWC may b e used. This one-page
certificate is intended for such work as the addition of a socket-outlet o r lighting point
to an existing circuit, or for a repair or modification
to each circuit worked on. Where
multiple circuits are worked on, all of the work could b e detailed on a n EIC.
A MEIWC must not b e used for t h e replacement of a consumer unit.
The MEIWC (Form 4) is included here, taken from Appendix 6 of BS7671. Notes o n
completion and guidance for recipients are provided with the form.
5.3
Periodic inspection and testing
The inspection and testing of an existing electrical installation is reported o n using an
EICR(Form 5). As with an EIC, this document is issued with the appropriate number
of generic Schedule(s)of Circuit Details and Test Results (Form 3).
For periodic inspections, the Schedule of Inspections for initial verification (Form 2)
should not b e used. The dedicated model suggested in BS7671 (Form 6) may b e used
for inspections of domestic installations a n d installations up to 1 0 0 A. For larger and
m o r e complex installations, t h e inspector will need to formulate bespoke inspection
schedules. These should be based on the requirements
of Regulation 642.3 and t h e
list of examples of items requiring inspection for an EICRwhich are applicable, given
in Appendix 6 of BS7671.
150
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
5
5.4
Examples of completed model forms for
certification and reporting
▼ Figure 5.1 Example Electrical Installation Certificate (EIC) (page 1)
ELECTRICAL INSTALLATION CERTIFICATE
(REQUIREMENTS FOR ELECTRICAL INSTALLATIONS
- BS 7671)
Certificate No.: ...555514
DETAILS OF THE CLIENT
Galbraith ...instruction
St, Paul's VJag K Leeds LSg. OMCj .......................................................................
INSTALLATION ADDRESS , , .x , _
_
,
_
,
„ . _
x
Un/t 3 , The Quadrant, Sovnetown Business
.......................................Park, .Sawetawn..SL1.QZZ.......................................................................
DESCRIPTION AND EXTENT OF THE INSTALLATION
Description of installation:
Complete electrical installation,
New installation
|?[
Addition to an
existing installation
i—i
Alteration to an
existing installation
|—|
new Z-floor office building
Extent of installation covered by this Certificate:
Complete electrical installation, comprising main switchboard, submains and distribution boards. To include all power and lighting
circuits, excluding car park lighting (supplied from adjacent building)
(Use continuation sheet if necessary)
u
_______See continuation sheet No: ........
FOR DESIGN
l/We, being the person(s) responsible for the design of the electrical installation (as indicated by my/our signatures below), particulars
of which are described above, having exercised reasonable skill and care when carrying out the design, hereby CERTIFY
that the design work for which l/we have been responsible is to the best of my/our knowledge and belief in accordance with
BS 7671:2018, amended to .ZQZZ(date) except for the departures, if any, detailed as follows:
Details of departures from BS 7671 (Regulations 120.3, 133.1.3 and 133.5):
Details of permitted exceptions (Regulation 41 1.3.3). Where applicable, a suitable risk assessment(s) must be attached to this Certificate.
Risk assessment attached
The extent of liability of the signatory or signatories is limited to the work described above as the subject of this Certificate.
For the DESIGN of the installation:
Signature: ......
............
Signature: ..................................
**(Where there is mutual responsibility for the design)
Date: 7/C?7/ >22Name (IN BLOCK LETTERS): ...... P.
Date: ...............
............................ Designer No 1
Name (IN BLOCK LETTERS): .................................................. Designer No 2**
FOR CONSTRUCTION
I, being the person responsible for the construction of the electrical installation (as indicated by my signature below), particulars of
which are described above, having exercised reasonable skill and care when carrying out the construction hereby CERTIFY that the
construction work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2018,
amended to P.
-.(date) except for the departures, if any, detailed as follows:
Details of departures from BS 7671 (Regulations 120.3 and 133.5):
None
The extent of liability of the signatory is limited to the work described above as the subject of this Certificate.
For CONSTRUCTION of the installation:
Signature:
..........
Date:
.P.7/. 2 Name (IN BLOCK LETTERS): .......P.kLNNETH..................... Constructor
FOR INSPECTION & TESTING
I, being the person responsible for the inspection & testing of the electrical installation (as indicated by my signature below), particulars
of which are described above, having exercised reasonable skill and care when carrying out the inspection & testing hereby CERTIFY
that the work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2018,
amended to2Z?.2r£.(date) except for the departures, if any, detailed as follows:
Details of departures from BS 7671 (Regulations 120.3 and 133.5):
None
The extent of liability of the signatory is limited to the work described above as the subject of this Certificate.
For INSPECTION AND TESTING of the installation:
Signature:
.............
Date:27/O7/2C>22Name (IN BLOCK LETTERS): .......
....................... Inspector
NEXT INSPECTION
l/We, the designer(s), recommend that this installation is further inspected and tested after an interval of not more than
......
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
151
5
▼ Figure 5 . 2 Example Electrical Installation Certificate (EIC) (page 2)
Certificate No.:
PARTICULARS OF SIGNATORIES TO THE ELECTRICAL INSTALLATION CERTIFICATE
Designer (No 1) N a m e ;
P JpnfcS
Company:
Address: .... E A.tejp rise . Way,. .
..............................................................................................
.......................................................................... Postcode:
Tel No: ....
.
Designer (No 2)
(if applicable)
/A.
Company:
Address;
Tel No:
Postcode:
Constructor
R
Ngme;
................................ Company:
........................................
Address: . ..
. P.
Clt .ScQtlavyd
................................................................
Postcode: .EH&k-.&QU.
Tel No:
Inspector
Name:
Address:
Company:
Electrics
....................................
g
SUPPLY CHARACTERISTICS AND EARTHING ARRANGEMENTS
Supply Protective Device
Nature of Supply Parameters
Number and Type of Live
Earthing
Conductors ______
arrangements
m
AC 0
DC
TN-C
Nominal voltage, U I Uo <K?.C?Z2;3C?V BS(EN)
1 -phase, 2-wire
2-wire
TN-S
Nominal frequency,
5Q. ...... Hz Type ........... U. ...............
2-phase,
3-wire
3-wire
TN-C-S
Prospective fault current, l p / 2J
kA Rated current ...7PP.
A
3-phase, 3-wire Q,
Other
TT
External earth fault
loop impedance, Ze(2)
P.:P.P.. Q
3-phase, 4-wire [V]
IT
(Note:(1) by enquiry (2) by enquiry or by measurement)
Confirmation of supply polarity
0
Other sources of supply (as detailed o n attached schedule)
N/A
PARTICULARS OF INSTALLATION REFERRED TO IN THE CERTIFICATE
Maximum Demand
Means of Earthing
.......................................................................
-kWW Amps (Delete as appropriate)
Maximum demand (load)
Distributor’s facility [Zf
Details o f Installation Earth Electrode (where applicable)
Type (e.g. rod(s), tape etc)
N/A..
Installation earth
Location
electrode
Q
Electrode resistance to Earth
Main Protective Conductors ___________________
g.
Ef
~|
Earthing conductor
Main protective bonding
conductors
Material .......
csa
7.P...... mm 2
Connection / continuity verified
[Zf
.. . . Copper
Material ........... L.C
csa
7.P..... mm 2
Connection / continuity verified
[Zf
To gas installation pipes IZl
| To oil installation pipes EN/4
To structural steel
N/A
Toother
Specify .N/A ...............................................................................................................
To wateZinstallation pipes
To lightning protection
N/A
Location
.
BS(EN)
No of poles
. SWftf hroovyy
A
A
V
If RCD main switch
RCD Type
NZA ....................
Rated residual operating current (l An)
Rated time delay
Measured operating time
Current rating ..7.QP.
Fuse / device rating or setting
Voltage rating ..4PP
.NZA
Outcome
Z / N/A
Item
No.
Description
8.0
9.0
10.0
Circuits (Distribution and Final)
Isolation and switching
Current-us
equipment
(permanently connected)
4........
.mA
.ms
.ms
Schedule of Inspections
Item
No.
1.0
2.0
3.0
Description
1
Condition of consumer's intake equipment
(Visual inspection only)
' z
1
Parallel or switched alternative
sources of supply
Protect!
measure:
Automatic Disconnection of Supply (ADS)
N/A
Bas protection
4.0
5.0 ___ Protective measures other than ADS __________
6.0
Addition
protection
7.0
Distributi
equipment
Z
z
z
z
z
Outcome
Z/n/A
11.0
Identification and notices
z
z
z
12.0
13.0
Location(s) containing a bath or shower
Other special installations or locations
N/A
N/A
14.0
Prosumer's low voltage electrical
installation(s)
N/A
COMMENTS ON EXISTING INSTALLATION (in the case of an addition or alteration see Regulation 644.1 .2):
...None................................................................................................................................................................
SCHEDULES
This Certificate is valid only when.
.Schedules of Circuit Details and Test Results are attached.
(Enter quantities of schedules attached).
ELECTRICAL INSTALLATION
NOTES (from
1
B S 7671)
The Electrical Installation
•
the initial
certification
a n existing
installation
•
t h e replacement
•
certifying
works
CERTIFICATE
is t o b e u s e d f o r :
of a new installation
or f o r a n addition
where
have been
new circuits
of a c o n s u m e r unit/distribution
for where
to the
Certificate
there
are multiple
existing installation
alternative to the issue of multiple
152
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
which
d o not
introduced,
board,
additions,
o r alteration
or
or
or alterations
extend
to
to new
or remedial
circuits
as a n
Minor Electrical Installation Works Certificates.
5
It i s not to be u s e d f o r a periodic
Installation
inspection
C o n d i t i o n R e p o r t should
and testing,
f o r which
b e u s e d . For a n addition
a n Electrical
or a l t e r a t i o n which
d o e s n o t e x t e n d t o t h e i n t r o d u c t i o n of n e w circuits, a M i n o r Electrical I n s t a l l a t i o n
Works Certificate m a y b e used.
The 'original' Certificate is to be issued to the person ordering the work (Regulation 644.4).
A duplicate
2
to
3
should
b e r e t a i n e d by the p e r s o n issuing the certificate.
T h i s C e r t i f i c a t e is o n l y valid if t h e S c h e d u l e o f I n s p e c t i o n s h a s b e e n c o m p l e t e d
c o n f i r m t h a t all r e l e v a n t i n s p e c t i o n s h a v e b e e n c a r r i e d o u t a n d w h e r e
accompanied
by S c h e d u l e ( s ) of Circuit Details
The signatures
appended
a r e those
e x e c u t i n g t h e w o r k of design,
a n d Test
Results.
of the p e r s o n s a u t h o r i z e d by the companies
c o n s t r u c t i o n , i n s p e c t i o n a n d t e s t i n g respectively.
A s i g n a t o r y a u t h o r i z e d t o c e r t i f y m o r e t h a n o n e c a t e g o r y o f w o r k s h o u l d sign i n
each
of t h e a p p r o p r i a t e p l a c e s . ( W h e r e a single
Certificate
is used,
construction,
4
the
inspection
person
authorized
a n d testing
The time interval recommended
for
signature
executing
Electrical I n s t a l l a t i o n
the
design,
before the first periodic inspection must be inserted.
T h e p r o p o s e d d a t e f o r t h e n e x t i n s p e c t i o n s h o u l d t a k e into
consideration t h e
f r e q u e n c y a n d q u a l i t y of maintenance
t h a t t h e installation
c a n reasonably b e
e x p e c t e d t o receive
life,
should
during
b e t w e e n t h e designer,
5
w o r k of
shall sign the certificate.)
its intended
a n d the
period
b e agreed
installer a n d o t h e r r e l e v a n t p a r t i e s .
T h e p a g e n u m b e r s f o r t h e S c h e d u l e ( s ) of Circuit D e t a i l s a n d Test Results s h o u l d
b e indicated,
together
with
the
total
n u m b e r of
pages
a s s o c i a t e d with
the
c e r t i f i c a t i o n provided.
6
T h e m a x i m u m p r o s p e c t i v e v a l u e of f a u l t c u r r e n t (I P f) recorded
s h o u l d b e the
g r e a t e r of e i t h e r t h e p r o s p e c t i v e v a l u e of s h o r t - c i r c u i t c u r r e n t o r t h e p r o s p e c t i v e
value of e a r t h f a u l t current.
GUIDANCE
F O R RECIPIENTS (to b e appended
t o the C e r t i f i c a t e )
T h i s s a f e t y C e r t i f i c a t e h a s b e e n i s s u e d t o c o n f i r m t h a t t h e e l e c t r i c a l installation w o r k t o
which
with
it relates h a s been
designed,
constructed,
inspected
and tested
in a c c o r d a n c e
BS 7671.
Y o u s h o u l d h a v e r e c e i v e d a n 'original' C e r t i f i c a t e a n d t h e p e r s o n t h a t i s s u e d t h e
Certificate
should
have r e t a i n e d a duplicate.
but not the o w n e r of the installation,
If you were the person
you should
it i n c l u d i n g the s c h e d u l e s , immediately
ordering
p a s s this Certificate,
to t h e owner.
T h e 'original' C e r t i f i c a t e s h o u l d b e r e t a i n e d i n a safe p l a c e a n d b e shown
inspecting
o r undertaking
f u r t h e r work
you later v a c a t e t h e property,
the work,
o r a f u l l copy of
on t h e e l e c t r i c a l installation
to a n y p e r s o n
i n the
future.
t h i s C e r t i f i c a t e will d e m o n s t r a t e t o the new owner
If
that
t h e e l e c t r i c a l i n s t a l l a t i o n c o m p l i e d w i t h t h e r e q u i r e m e n t s of B S 7 6 7 1 a t t h e t i m e
t h e C e r t i f i c a t e w a s i s s u e d . T h e C o n s t r u c t i o n (Design
require
that,
f o r a p r o j e c t covered
together
with
schedules,
by those
a n d Management)
Regulations,
is i n c l u d e d i n t h e project
a copy
Regulations
of this Certificate,
h e a l t h a n d safety documentation.
For safety reasons, t h e electrical installation will n e e d to b e inspected at appropriate intervals
by a skilled person
recommended
or persons, competent
before the next inspection
in such work. The maximum
time
interval
is stated on Page 1 under 'NEXT INSPECTION'.
G u i d a n c e N o t e 3 : I n s p e c t i o n & Testing
© The Institution
o f Engineering
and Technology
153
This Certificate is intended to b e issued only for a new electrical installation or for new
work associated with an addition or alteration to an existing installation. It should not
have b e e n issued for t h e inspection and testing of an existing electrical installation.
An "Electrical Installation Condition Report" should b e issued for such an inspection.
This Certificate
is only valid if the Schedule of Inspections has been completed
to
confirm that all relevant inspections have been carried out and where accompanied
by Schedule(s) of Circuit Details a n d Test Results.
Where the installation includes a residual current device (RCD) it should b e tested
six-monthly by pressing the button marked T or 'Test'. The device should switch off
the supply and should then be switched on to restore the supply. If the device does
not switch off the supply when the button is pressed, seek expert advice. For safety
reasons it is important that this instruction is followed.
Where the installation includes an arc fault detection device (AFDD) having a manual
test facility it should b e tested six-monthly by pressing the test button. Where a n AFDD
has both a test button and automatic test function, manufacturer's
b e followed
instructions shall
with respect to test button operation. Where the installation includes a
surge protection device (SPD)the status indicator should b e checked to confirm it is in
operational condition i n accordance with manufacturer's information. If t h e indication
shows that t h e device is not operational, seek expert advice. For safety reasons it is
important that this instruction is followed.
Where the installation includes
alternative or additional sources of supply, warning
notices should b e found at the origin or meter position, or if remote f r o m the origin,
at the consumer unit or distribution board and at all points of isolation of all sources
of supply.
154
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Generic schedule of circuit details for a single-phase installation
▼
Figure
5 . 3 E x a m p l e S c h e d u l e of C i r c u i t Details (single-phase
installation)
GENERIC SCHEDULE OF CIRCUIT DETAILS
Certificate/Report
number:..
"?.
Distribution board details
Consumer
DB reference:
Location:
Under stairs cupboard Supplied from:
Supply
meter
Unit
Distribution circuit OCPD: BS (EN):
SPD Details:
Type(s)*: T1
1361
T2 gf
_________ Type:
t
T3 D
H
80
Rating/Setting:
A
N/AD
CIRCUIT DETAILS
102#
8
2x2.5
1.5
61001
A
A
A
1
1O1#
7
2x6.0
2X1.0
2.5
1.0
61001
61001
A
A
1OO#
7
7
Lights - downstairs
Lights - garage
8
7
2X1.0
2X1.0
1.0
1.0
8
SPARE
-
-
-
5*
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
<c>
socket- outlets
-
B
B
B
32
6
6
32
1.37
1.37
14
61001
61001
Rating (A)
Maximum permitted Zs (Q)§
Breaking capacity (kA)
Rating (A)
-
A
Cooker - kitchen
Lights - upstairs
61001
61001
O
Ring - kitchen
4
102#
ID
cpc (mm 2)
3
2
Type
Live (mm2)
BS (EN)
o>
00
Number of points served
cn
Reference method*
Type of wiring
w
1.5
1.5
(D
IS
2X2.5
2X2.5
102.#
(Viu) "’i
IO
8
A
A
?
2
Number & size
Ring - downstairs
socket- outlets
Ring - upstairs socket- outlets
1
RCD
(N3) sa
Circuit description
Overcurrent protective device
______
Circuit number
Conductor details
A
30
32
A
39
32
32
6
1.37
61001
A
39
32
B
B
32
1.37
61001
61001
A
39
32
6
6
6
A
50
6
61001
61001
B
B
6
6
6
6
7.28
61001
61001
A
7.28
A
50
50
6
6
-
-
-
-
-
-
-
-
-
7.28
CODES FOR TYPES OF WIRING
A
Thermoplastic
insulated/
s h e a t h e d cables
c
B
Thermoplastic
cables
metallic conduit
in
Thermoplastic
non-metallic
D
cables in
conduit
Thermoplastic cables
metallic trunking
F
E
in
Thermoplastic
non-metaliic
cables i n
trunking
G
H
0
Other
Thermoplastic
SWA cables
Thermosetting
SWA cables
Mineral
- please
state
insulated cables
155
* SPDType. Where a combined T1 + T2 orT2 + T3 device is installed, indicate by ticking both Type boxes.
t Where a T3 SPD is installed to protect sensitive equipment, enter details in Remarks’, column 31 , of the Schedule of Test Results. (See Section 534 of BS 7671;2018+A2:2022.)
t See Table 4A2 of Appendix 4 of BS 7671 :2018+A2:2022.
§ Where the maximum permitted earth fault loop impedance value slated in column 12 is taken from a source other than the tabulated values given in Chapter 41 of BS 7671 :2018+A2:2022, state the source of the data in the appropriate cell for the circuit in the ‘Remarks’, column 31, of the Schedule of Test Results.
5
Generic schedule of circuit details - Notes
The fields of the f o r m are used as follows:
1
The circuit number as marked o n the distribution board or consumer unit. The
normal convention
for single-phase distribution
boards and consumer
units,
circuit 1 is closest to t h e main isolator of the assembly. For single-phase circuits
in three-phase installations, it is preferred to use the designation L I , L2, L3.
For example, for single-phase circuits in the fifth compartment, the designation
would b e 5L1, 5L2 and 5L3.
2
3
Brief description of t h e circuit.
The type of wiring is identified by a code, following
b o t t o m of t h e form.
4
The reference method
is identified
5
BS 7671.
The number of points
served is the total number
according
the convention
at t h e
to Table 4 A 2 in Appendix 4 of
of accessories or other
connection points for current-using or generating equipment. A double or triple
socket-outlet to BS 1363-2 is usually considered to b e a single point.
6
Number
and size of live conductors.
this should also b e identified
example:
•
•
Where the conductors
using the chemical
are not copper,
symbol in this column.
For
2x1.5 indicates two copper live conductors with cross-sectional area 1.5 m m 2 ;
4 x 1 6 Al indicates four aluminium
live conductors with cross-sectional area
1 6 m m 2.
7
Number and size of cpc. Where the conductors are not copper, this should also
b e identified using the chemical symbol in this column.
8
9
Number of the standard for the overcurrent protective device, for example:
•
’ 6 0 8 9 8 ' for an MCB to BS EN 60898;
•
' 3 0 3 6 ' for a re-wireable fuse BS 3 0 3 6 .
Type of overcurrent protective device, where applicable. For example, B, C or D
for MCBs and RCBOsto BS EN 6 0 8 9 8 or BS EN 61009.
10 Rated operating current l n of the overcurrent protective device.
11 Rated breaking capacity o f t h e overcurrent protective device.
12 Maximum permitted earth fault loop impedance Z s of the circuit for automatic
disconnection of supply. These figures are usually obtained f r o m Tables 41.1 to
41.6 in BS 7671 (see Appendix A). Where table 41.5 of BS 7671 applies for
TT systems served by a public supply, an earth fault loop impedance
exceeding
2 2 5 Q is unlikely to b e acceptable, as this implies the earth electrode resistance
is unlikely to b e stable as indicated in the Note to Table 41.5 of BS 7671.
13 Number of the standard for the RCD protecting the circuit (if any), for example
'610009'
for an RCBO to BS EN 61009.
14 Type of t h e RCD protecting t h e circuit (if any), either 'AC','A’,'F' or 'B'.
15 Residual current rating of the RCD protecting the circuit (if any).
16 Maximum operating current of t h e RCD protecting the circuit (if any).
156
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Generic Schedule of Test Results for a single-phase installation
▼
Figure
5 . 4 E x a m p l e S c h e d u l e of Test Results (single-phase
installation)
GENERIC SCHEDULE OF TEST RESULTS
Certificate/Report number: . . .
Details of test instruments used (serial and/or asset numbers)
Distribution board details
0.2
db
Correct polarity gf
SPD:
Operational status confirmed
|
Multifunction:
S e r 1020304
Continuity: _ _ ____ _______N/A
_ _________________ _ _ _
Insulation resistance:
N/A
Earth fault loop impedance: N/A
RCD:. . . .............................. N/A
Earth electrode resistance: _N/A ..... ........................... ............
0 . 2 kA
pf
Phase sequence
[?f
N/A
TEST RESULT
©
g g
§ 8
™
500
>999
N/A
N/A
500
>999
>999
500
>999
>999
2
0.62
0.62
1.02
0.41
3
0.22
0.22
0.37
0.15
4
N/A
N/A
N/A
N/A
0.16
5
N/A
N/A
2.56
6
N/A
N/A
7
N/A
N/A
N/A N/A
1.57
N/A
N/A
8
N/A
8.20
N/A
N/A
N/A
N/A
N/A
>999
500
>999
>999
250
N/A
>999
500
>999
>999
500
>999
>999
N/A
N/A
N/A
J
J
Y
J
N/A
CO
Disconnection
N/A
0)
5
Maximum measured
0.41
22
>
0.71
28
ro
1.02
u?
1
M
O>
Polarity#
0.62
CJ1
Live - Earth (MQ)
r n (neutral)
0.62
w
Test voltage (V)
00
r, (line) (0)
1
24
Q.
20
RCD
Z.(O)
(R 1 + R 2) or R 2
(R, + R 2 )
=4
Circuit number
Ring final circuit
Insulation resistance
AFDD
time (ms)**
Continuity (Q)
DETAILS
0.71
36
</
0.44
25
J
N/A
N/A
J
N/A
N/A
N/A
N/A
N/A
0.46
34
2.85
29
2.86
33
1.90
31
N/A
N/A
N/A
CD
-I f o
Q THOMPSON
o
I
<8
Signature:
G
Date:
1S/O7/
fl Not all SPDs have visible functionality indication.
# Where this schedule is issued with an Electrical Installation Condition Report, and incorrect polarity is identified, an 'X' should be entered.
** RCD effectiveness is verified using an alternating current test at rated residual operating current (lAn)ft Not all AFDDs have a test button
Remarks
Include details of circuits and/or installed equipment
vulnerable to damage when testing
(continue on a separate sheet if necessary)
31
N/A
<§•
Tested by name (Capitals):
Manual test button operation
Confirmed:
q
o
Unit
£1
Test button operation
Consumer
to
LD
DB reference:
2.022
Circuit S insulation 2.50 V (L+N)-E due to LEO drivers
High Zs on U/S lighting (circuit 6) found to be due to loose
terminals at the point of connection of additional lighting
circuitry. With the additional circuitry disconnected } a
satisfactory Zs of 2.86 O. was obtained. Conductors remain
damaged and cabling requires replacement.
58
Form 2 Generic Schedule o f Circuit Details f o r a three-phase installation
installation)
GENERIC SCHEDULE OF CIRCUIT DETAILS
Certificate/Report number:..5*333 7 3
Distribution board details
DB reference:
Location:
Distribution circuit OCPD: BS (EN):
SPD Details: Type(s)*: T 1
Switch
88-3
T2 gf
Room
Type:
f
T3 D
Supplied from:
Supply
Rating/Setting:
80
meter
A
N/A
CIRCUIT DETAILS
o
Rating (A)
Breaking capacity (kA)
Maximum permitted Z s (Q)§
£
Type
B
1
4x2.5*
1X10
608 9 8
B
6
IO
7.28
N/A
N/A
N/A
N/A
E
B
14
2x4.0
1X1.5*
61009
B
32
IO
1.37
61009
A
30
32
A
A
N/A
30
16
30
32
N/A
N/A
A
N/A
30
32
N/A
N/A
co
BS (EN)
00
o»
Number of points served
C
U1
Type
floor North
cpc (mm 2)
- ground
Live (mm2)
SPPs
R/ng
Reference method*
1
2.L1
15 ~~
Number & size
co
2
RCD
(ns) sa
Circuit description
Overcurrent protective device
Type of wiring
Conductor details
Circuit number
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
▼ Figure 5 . 5 Example Schedule of Circuit Details (three-phase
2.L2.
External
lighting
G
C&P
16
2x2.5*
1X2-5*
61009
B
16
IO
2.73
61009
2L3
Radial - Kitchen
A
102#
7
2X4.0
1X1.5*
61009
B
32
IO
1.37
61009
3L1
Lighting
C
B
23
2X2.5*
1X2.5*
608 9 8
B
16
IO
2.73
N/A
3L2
Ring
1.37
61009
Lighting
32
16
IO
3L3
IO
2.73
N/A
4L1
Radial - fire
- ground
- ground
floor South & Circulation
floor South
QC
E
B
1X1.5*
61009
B
B
14
27
2x4.0
C
2X2.5*
1X2. 5
608 9 8
B
B
1
2x2.5*
1X2.5*
608 9 8
B
IO
IO
4.37
N/A
N/A
B
8
2X4.0
1x1.5
61009
B
32
IO
2.73
61009
N/A
A
N/A
floor Receptions Circulation
B
E
30
32
B&D
B
5*
2X4.0
1X1.5
60898
B
20
IO
2.19
N/A
N/A
N/A
N/A
E
1
4X2.5*
1x22 Fe
60947-2
C
25*
IO
0.87
60947-2
B
30
25*
floor North
alarm
412
Ring
4L3
Radial - a/c plant room
___5
Laundry
6
I
16
& Reception
- ground
- ground
1
- 3ph washing
a
machine
SPARE
CODES FOR TYPES OF WIRING
B
A
Thermoplastic
sheathed
insulated/
cables
Thermoplastic
cables in
metallic conduit
c
Thermoplastic
non-metallic
D
cables in
conduit
Thermoplastic
cables
metallic trunking
E
in
Thermoplastic
non-metallic
F
cables in
trunking
G
H
0
Other
Thermoplastic
SWA cables
Thermosetting
SWA cables
Mineral
insulated
- please state
cables
* SPD T)pe. Where a combined T1 + T2 or T2 + T3 device is installed, indicate by ticking both Type boxes.
•f Where a T3 SPD is installed to protect sensitive equipment, enter details in ‘Remarks', column 31, of the Schedule of Test Results. (See Section 534 of BS 7671:201 8+A2:2022. )
t See Table 4A2 of Appendix 4 of BS 7671 ;2018+A2:2022.
§ Where the maximum permitted earth fault loop impedance value stated in column 12 is taken from a source other than the tabulated values given in Chapter 41 of BS 7671:201 8+A2:2022, state the source of the data in the appropriate cell for the circuit in the ‘Remarks’, column 31, of the Schedule of Test Results.
Form 3 Generic Schedule of Test Results for part of a three-phase installation
▼
Figure
5 . 6 E x a m p l e Schedule of Test R e s u l t s (three-phase
installation)
GENERIC SCHEDULE OF TEST RESULTS
Certificate/Report number:
Distribution b o a r d details
575.
Details of test instruments u s e d (serial and/or asset n u m b e r s )
D B reference:
.....QBX .............
Z db ____O»3O
Confirmed:
Correct polarity |Vf
SPD:
Operational status confirmed
______ __________
Q
I f
____ 0,8
__
... _____
M ultifu notion: ................. ....... . .Ser 1022305
Continuity:
................
N/A
Insulation resistance:
N/A
E a r t h fault l o o p impedance:
N/A
RCD:
.....
_ N/A
Earth electrode resistance: ..... ..... N/A
kA
P h a s e sequence [Vf
|Vf
N/A
..................... ....... .........
TEST RESULT DETAILS
3L2
0.51
3L3
N/A
N/A
5
Manual test button operation+t
N/A
N/A
N/A
N/A
N/A
250
500
250
500
250
500
250
>999
>999
>999
N/A
>999 >999
>999
N/A
>999 >999
>999
N/A
0.52 N/A
0.42 N/A
1.15 N/A
0.42 N/A
500
500
500
500
>999 >999
>999 >999
>999 >999
>999 >999
CD
O
26
J
/
31
N/A
N/A
0.91
52
1.65
22
J
23
O.S4
1 . 3 2 N/A
N/A
J
25
0.92
0 . 2 1 N/A N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Insulation 250 V (Ll+L2 L3-t-N)-E: SPDs in circuit *
Y
/
</
J
/
J
M a x i m u m measured
Live - Earth ( M Q )
U1
N/A
1.39
N/A
N/A
NJ
N/A
N/A
N/A
1.20
N/A
X.8X
Live - Live ( M Q )
N/A
N/A
Test voltage (V)
22
0.00
0.61
1.35
0.54
1.02
0.62
0.51
W
21
0.00
NJ
r 2 (cpc)
rn (neutral)
N/A
0.51
N/A
N/A
o
Guidance Note 3: Inspection & Testing
s Institution of Engineering and Technology
3 LX N/A
N/A
N/A
N/A
0.67
N/A
of
*
AFDD
Test button operation
©
0.00
0.65
of
+
RCD
Z,(Q)
(R. + R J o r R 2
o
0.00
0.65
2L1
2.L2.
N/A
2.L3 N/A
3 L 1 N/A
0.67
3L2
3L3 N/A
1
<D
2
r, (line) (0)
Circuit n u m b e r
R i n g final circuit
Insulation resistance
0.30
Disconnection t i m e (ms)**
Continuity ( Q )
Remarks
Include details of circuits and/or installed equipment
vulnerable to d a m a g e w h e n testing
(continue o n a separate s h e e t if necessary)
Insulation 250 V (L.+N)-E: dawn to dusk sensors
Insulation 250 V (L N)-E: PIRs in circuit *
Insulation 250 V (L+N)-E: PIRs in circuit
0 . 2 2 N/A N/A N/A
0.72
21
N/A
1.36 N/A
N/A
N/A
J
0.20
34
N/A
6
Tested
by n a m e (Capitals):
Signature:
6? WILSON
Date:
2 2 Ju ly 2022
159
U Not all SPDs have visible functionality indication.
# Where this schedule is issued with an Electrical Installation Condition Report, and incorrect polarity is identified, an 'X' should be entered.
** RCD effectiveness is verified using an alternating current test at rated residual operating current ( lAn ).
tt Not all AFDDs have a test button
* Cables for these circuits were tested at 500 V L-L,
L - N , L-E and N-E as appropriate, prior to
connection of sensitive equipment in circuit.
All readings > 9 9 9 Mil.
5
GENERIC SCHEDULE OF TEST RESULTS
NOTES
The following notes relate to the column number in the f o r m (Form 3).
17 The circuit number as marked o n t h e distribution board or consumer unit. The
normal convention
for single-phase
distribution boards and consumer units,
circuit 1 is closest to t h e main isolator of t h e assembly. For single-phase circuits
in three-phase installations, it is preferred to use the designation
LI, L2, L3.
For example, for single-phase circuits in the fifth compartment, the designation
would b e 5L1, 5L2 and 5L3.
18 Ring line-line open resistance continuity in Q : see Section 2.6.6.
19 Ring neutral-neutral open resistance continuity in Q: see Section 2.6.6.
20 Ring cpc-cpc open resistance continuity in Q : see Section 2.6.6.
21 Ring (R] + R2) : enter the highest value recorded while carrying out step 3 of
t h e ring continuity test (see Section 2.6.6). Note that where meaningless results
are recorded, due to parallel return paths, and it has been established and t h e
inspector has verified continuity, a value is not necessary in this cell, and the
cell may b e ticked.
2 2 Continuity
R2 : a d d the value of t h e cpc continuity reading. If using test m e t h o d
2 (the 'wandering
lead' method),
readings that were
measured o n the circuit. Note that where
enter the m a x i m u m value of the various
meaningless
results are recorded, d u e t o parallel return paths, and it has b e e n established
and the inspector has verified continuity,
a value is not necessary in this cell,
and the cell may b e ticked.
2 3 Insulation resistance test voltage: usually 5 0 0 V unless the circuit contains
equipment that m a y b e damaged by, or otherwise affect, a test at 5 0 0 V.
24 Insulation
resistance, L-L: enter the minimum
value recorded
during testing of
the circuit for each of t h e various configurations (see Section 2.6.7).
25 Insulation
resistance, L-E: enter t h e minimum
the circuit for each of the various configurations
value recorded during testing of
(see Section 2.6.7).
2 6 Polarity: tick this cell w h e n the polarity for the circuit has been confirmed (see
Section 2.6.13). A cross may b e use to indicate polarity only where the f o r m
accompanies an EICR.
2 7 Z s : enter t h e circuit EFLIby whatever method you have selected t o determine
it
(see Section 2.6.15).
28 Enter maximum disconnection t i m e measured for a test current at | An .
29 Tick this cell when t h e operation of the RCD is confirmed when pressing the
test button.
30 Tick this cell when AFDD that has a test button operates correctly w h e n the test
button is pressed.
3 1 Remarks: this cell is provided to note anything relevant to the circuit and testing.
160
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
▼ Figure
5.7 Example M i n o r Electrical Installation
Works Certificate (MEIWC)
MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE
Certificate No.: ...4.43g.
(REQUIREMENTS FOR ELECTRICAL INSTALLATIONS - BS 7671)
To be used only for minor electrical work which does not include the provision of a new circuit
PART 1: Description of the minor works
............................................. Date minor works completed
1 . Details of the Client . .&£.&.
.lighting
3. Description of the minor works
points
“3“#
202-2.
2A. Y. .............................................................
Little.
2. Installation location/address . 2 kP.YP,.
................................
t o .office/b
4. Details of any departures from BS 7671 :2018 as amended to 2022 (date) for the circuit altered or extended
(Regulation 120.3, 133.1.3 and 133.5).
Details of permitted exceptions (Regulation 411.3.3). Where applicable, a suitable risk assessment(s)
, ,m
.
must be attached to this Certificate.
Risk assessment attached |_|
None.
5. Comments on (including any defects observed in) the existing installation (Regulation 644.1.2):
No protection against overvoltage. Distributor's equipment issue - cut-out ruseholder corner cracked.
Customer- advised ■to ■contact -supplier ..............................................................................................................................
PART 2: Presence and adequacy of installation earthing and bonding arrangements (Regulation 132.16)
TN-C-S L3 TT
TN-S
1 . System earthing arrangement:
Q
2. Earth fault loop impedance at distribution board (Zdb) supplying the final circuit ........
3. Presence of adequate main protective conductors:
LET
Earthing conductor
Main protective bonding conductor(s) to: Water E Gas S Oil
Structural steel
Other (Specify)..................
PART 3: Circuit details
DB Reference No.: ....... /. ................................. DB Location and type: . Tpp.of .stairs, 8
Circuit description: ...... Qpstgjrs, lighting .......................... Installation reference method .................
Circuit No.:
..... mm 2 cpc .... A4?........... mm 2
Number & size of conductors: Live .
Circuit overcurrent protective device: BS (EN) ..£■£<?<?.?... Type
RCD:
BS (EN) ..£*£*?.?..
Type .....4...
..... Rating ,.A
AFDD: BS (EN)
SPD:
PN. .....................................
Rating ..... .f...A
Rating ..... £ . . A
Rated residual operating current (I J ....
..mA
..A
..... Type
BS(EN) ...W*
PART 4: Test results for the altered or extended circuit (where relevant and practicable)
R 2)......................................... Q or R 2 .................. <24 ............... Q
Protective conductor continuity:
(R
Continuity of ring final circuit conductors:
L/l ___bt/A. ........... Q N/N .....
Insulation resistance:
Test voltage3Z?<?.V Live - Live Z.9.9.9MQ
Polarity satisfactory:
Live - Earth .>9.9.9...
Maximum measured earth fault loop impedance:
0
MQ
Zs
Q
Satisfactory test button operation:
RCD disconnection time at rated residual operating current (l An) .../2-?-4.ms
AFDD satisfactory test button operation:
SPD functionality confirmed: Q
.......... Q cpc/cpc ...... bf/A ........ Q
NOTE: Not all AFDDs have a test button
NOTE: Not all SPDs have visible functionality indication
PART 5: Declaration
I certify that the work covered by this certificate does not impair the safety of the existing installation and the work has
been designed, constructed, inspected and tested in accordance with BS 7671:2018 amended to .4<?42..... (date)
and that to the best of my knowledge and belief, at the time of my inspection, complied with BS 7671 except
as detailed in Part 1 above.
Name: ..... G.-..Stokes .................................................
For and on behalf of: ...StP.keS.El
Address; . ..
....................................
Signature:
Newtown
Position: ...P.UC Etor .................................................
WA4
SXX
Date;
Au
uStjZOZZ
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
161
5
MINOR ELECTRICAL INSTALLATION WORKS CERTIFICATE(MEIWC)
Notes for the person producing the Certificate
Scope
The MEIWC is intended to be used for alterations or additions to an installation that do
not extend to the provision of a new circuit. Examples include the addition of socket
outlets or lighting points to an existing circuit, the relocation of a light switch, and
similar. This Certificate may also be used for the replacement of equipment such as
accessories or luminaires, but not for the replacement of distribution boards, consumer
units or similar items. Appropriate inspection and testing, however, should always be
carried out, irrespective of the extent of the work undertaken.
Part 1 Description of the minor works
1,2,3
4
5
The minor works must be so described that the work that is the subject of
the certification can be readily identified.
See Regulations 120.3 and 133.5. No departures are to be expected, except
in the most unusual circumstances. See also Regulation 644.1.
Note any defects observed in the existing installation that are not related to
the work being carried out.
Under the "Comments on existing installation ..." heading, only deficiencies that do
not impair the safety of any alteration or addition covered by the Certificate may be
referred to. An example would b e existing main bonding conductors identified by
the colour green only (rather than green-and-yellow) or which have a csa less than
that required by Chapter 54, but which are nevertheless considered adequate by the
designer of the alteration or addition.
Any deficiency liable to impair the safety of the alteration or addition must be corrected
before the alteration or addition is carried out (see Regulation 132.16). It would be
unacceptable simply to refer to the deficiency on the Certificate.
Part 2 Installation earthing and bonding: existing installation
The existing earthing and bonding must be inspected and tested to confirm that it is
adequate for the new works. Any extension to earthing and bonding must be installed
for the works, if required.
Part 3 Circuit details
Generally, for domestic installations, this is simple: record details of the circuit protective
device and circuit conductors.
COMPLETE THE CIRCUIT CHART DETAILS ON THE DISTRIBUTION BOARD OR
CONSUMER UNIT.
Part 4 Essential tests
The relevant provisions of Part 6 (Inspection and testing) of BS7671 must be applied
in full to all minor works. For example, where a socket-outlet is added to an existing
circuit, it is necessary to:
162
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
5
(a) establish that t h e earthing contact of the socket-outlet is connected to a suitable
means of earthing via the MET;
(b) measure the insulation
resistance of t h e circuit that has been added to and
establish that i t complies with Table 6 4 of BS 7671;
(c) measure the EFLIto establish that the maximum
permitted
disconnection
time
is not exceeded;
(d) check that t h e polarity of t h e socket-outlet is correct; and
(e) if t h e work is protected by an RCD, verify the effectiveness of the RCD.
Part 5 Declaration
When filling out a n d signing a form o n behalf of a company or other business entity,
individuals m u s t state for w h o m they are acting.
GUIDANCE FOR RECIPIENTS (to be a p p e n d e d t o the Certificate)
This Certificate has been issued to confirm that t h e electrical installation work to which
it relates has been designed, constructed,
inspected and tested in accordance with
BS 7671.
You should have received an 'original' Certificate and t h e person that issued the
Certificate should have retained a duplicate. If you were the person ordering the work,
but n o t t h e owner of t h e installation, you should pass this Certificate, or a copy of
it, to the owner. A separate Certificate should have been received for each existing
circuit o n which minor works have been carried out. This Certificate is not appropriate
if you requested the person that issued the Certificate to undertake m o r e extensive
installation work, for which you should have received an EIC.
The Certificate
should b e retained in a safe place and b e shown to any person
inspecting or undertaking further work o n the electrical installation in the future. If
you later vacate the property, this Certificate will demonstrate to the n e w owner that
the minor electrical installation work carried out complied
with the requirements
of
BS7671 at the time t h e Certificate was issued.
For safety reasons, the electrical installation will need to b e inspected at appropriate
intervals by a skilled person or persons, competent
in such work.
Where the installation includes a residual current device (RCD) it should b e tested
six-monthly by pressing t h e button marked T
or 'Test'. The device should switch off
t h e supply and should then b e switched o n to restore t h e supply. If the device does
not switch off t h e supply w h e n the button is pressed, seek expert advice. For safety
reasons it is important that this instruction is followed.
Where t h e installation includes an arc fault detection device (AFDD) having a manual
test facility it should b e tested six-monthly by pressing the test button. Where a n AFDD
has both a test button and automatic test function, manufacturer's instructions shall b e
followed with respect to test button operation.
Where the installation includes a surge protection
device (SPD) the status indicator
should b e checked to confirm it is in operational condition in accordance with
manufacturer's information. If the indication shows that t h e device is n o t operational,
seek expert advice. For safety reasons it is important that this instruction is followed.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
163
5
Where the installation includes alternative or additional sources of supply, warning
notices should be found at the origin or meter position, or if remote from the origin,
at the consumer unit or distribution board and at all points of isolation of all sources
of supply.
▼ Figure 5 . 8 Example Electrical Installation Condition Report (EICR) (page 1)
ELECTRICAL INSTALLATION CONDITION REPORT
Report No.: . A 3 4 2
SECTION A. DETAILS OF THE PERSON ORDERING THE REPORT
Name
M.
.........................................................................................................................................
Address
EAiX
............................................................................................................
SECTION B. REASON FOR PRODUCING THIS REPORT
Date(s) on which inspection and testing was carried out ....... l.tL
August
,2022
..................................
SECTION C. DETAILS OF THE INSTALLATION WHICH IS THE SUBJECT OF THIS REPORT
Occupier
Address
Description of premises
Residential Ef
Commercial
Industrial
Other (include brief description)
Estimated age of wiring system
years
Evidence of additions I alterations?
Yes ST
No
Installation records available? (Regulation 651.1)
Not apparent
Yes □
If yes, estimate age
No |Vf
£ .........years
Date of last inspection
....................................... (date) __________
SECTION D. EXTENT AND LIMITATIONS O F INSPECTION AND TESTING
Extent of the electrical installation covered by this report
. a n d .test of c p
uwier unit
..Visual .inspeetion..o.f..suprilier!s..ter.nninal..eauipi(nent
i ..inspection.
Agreed limitations including the reasons (see Regulation 653.2)
Bu tiding. fabric
,not ,to b e , distu rbed
Agreed with: .....Client
....................... ................. ....... .......... ...................................................... ............................................................ ..........
Operational limitations including the reasons (see page no
) ...None
The inspection and testing detailed in this report and accompanying
as amended to
...............................
schedules have been carried out in accordance with BS 7671:2018
It should be noted that cables concealed within trunking and conduits, under floors, in roof spaces, and generally within the fabric of the building or
underground,
have not been inspected unless specifically agreed between the client and inspector prior to the inspection. An inspection should be
made within an accessible roof space housing other electrical equipment.
SECTION E. SUMMARY O F THE CONDITION
O F THE INSTALLATION
General condition of the installation (in terms of electrical safety)
.lnst.alLatio.n.d.Q.e$..nQt.cp.
.p
additional,
,i
Iighti
,,poin
.wlth..D$.7
7
alled, l.n2977.-.
:2Q
tA2:2Q22,.EidJS.in.gQQ.d.cpnditiQn.ApartJrp.rn.the..connect.lQn...Qf
.This, led to flickering , lights, and possible risk of fire
,and ,shock.
Overall assessment of the installation in terms of its suitability for continued use
SATISFACTORY / UNSATISFACTORY* (Delete as appropriate)
*An unsatisfactory
assessment indicates that dangerous (code C1) and/or potentially dangerous (code C2) conditions have been identified. _______
SECTION F. RECOMMENDATIONS
Where the overall assessment of the suitability of the installation for continued use above is stated as UNSATISFACTORY, 11 we recommend that
any observations classified as ‘Danger present’ (code C1 ) or ‘Potentially dangerous’ (code C2) are acted upon as a matter of urgency.
Investigation without delay is recommended for observations identified as ‘Further investigation required’ (code Fl).
Observations classified as ‘Improvement recommended’ (code C3) should be given due consideration.
13/08 /2.032
Subject to the necessary remedial action being taken, I / We recommend that the installation is further inspected and tested by ..................... (date)
for the following reasons
this. .is.t h e . usual. period, recommended,
for. private
. residences
SECTION G. DECLARATION
l/We, being the person(s) responsible for the inspection and testing of the electrical installation (as indicated by my/our signatures
below), particulars of which are described above, having exercised reasonable skill and care when carrying out the inspection and
testing, hereby declare that the information in this report, including the observations and the attached schedules, provides an accurate
assessment of the condition of the electrical installation taking into account the stated extent and limitations in section D of this report.
Report authorised for issue by:
Inspected and tested by:
Name (Capitals)
.......
fdECEE..TH.QM
.................
Name (Capitals)
PFF
THOMPSON
For/on behalf of . . . . T . a n d C , Electrical
Forton behalf of
Position
Position
Prwrfe.r
Address
Whiteleaf
..................................................................
SECTION H. SCHEDULE(S)
.....i
Inspection Schedule(s) and
Date
Schedule(s)
T.and.C
Electrical.
Proprietor
14
August
iozi
of Circuit Details and Test Results are attached.
The attached schedule(s) are part of this document and this report is valid only when they are attached to it.
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
..................................
................................................................
U/hrte/eaf Close, Ne
pwn .EA.4 SXX
Address
Close,
Date
164
...........................
Signature
Signature
Figure 5 . 9 Example Electrical Installation Condition Report (EICR) (page 2)
Report N o . : ...1342.
SECTION I. SUPPLY CHARACTERISTICS
Nature of Supply Parameters
Supply Protective Device
Conductors
DC
TN-C
AC Ef
TN-S
1 -phase, 2-wire
TN-C-S
AND EARTHING ARRANGEMENTS _________________________________________________________
Number and Type of Live
Earthing
arrangements
S’
TT
Nominal voltage, U / Uo
............ V
BS(EN) .....
.............
Nominal frequency, fW ......... so ........... Hz
Type ................? ................
2-phase, 3-wire
3-wire
Other
Prospective fault current, I P
..... &.?. ...... kA
External earth fault
loop impedance, Ze ..............
Q
Rated current
3-phase, 3-wire
3-phase, 4-wire
IT
.....
2-wire
EF
(Note:
Confirmation of supply polarity 0
.......1Q.9.. ... A
(1) by enquiry (2) by enquiry or by measurement)
Other sources of supply (as detailed on attached schedule) E
SECTION J. PARTICULARS OF INSTALLATION REFERRED TO IN THE REPORT ______________________________________________________
Details of Installation Earth Electrode (where applicable)
Means of Earthing
Distributor’s facility IZT
Type ............. NZA ............................................................................................................................................................
Installation earth
electrode
Location
......... W/A ..........................................................................................................................................................
Resistance to Earth
... N/A. .. O
Main Protective Conductors
________________________________________________
Material
Earthing conductor
Main protective bonding conductors
To water installation pipes
0
Connection / continuity verified
0
.......... csa ........ «?. .......... mm*
Connection / continuity verified
0
0
To structural steel
Material
To gas installation pipes
Toother
To lightning protection
....Copper,......... csa ....... .9........... mm 2
| To oil installation pipes
Specify .................................................................................................................................................
Main switch / Switch -fuse / Circuit-breaker I RCD
Location
........................................................
Current rating ........ 1Q.Q.................. A
Under-stairs cupboard
Fuse / device rating or setting
BS(EN) ......
4 7 - 3 ...........................
Voltage rating
.N/A
If RCD main switch
RCD Type ..........
.A
...............................................
Rated residual operating current (Jap) ...... .C/ZA...... m A
ZZQ .................. V
Rated time delay ........ NZA ..................................... ms
No of poles ...... £ ..........................................
Measured operating time .....
............................. ms
SECTION K. OBSERVATIONS
Referring to the attached inspection schedule(s) and schedule(s) of circuit details and test results, and subject to the limitations specified at the
Extent and limitations of inspection and testing section
No remedial action is required
The following observations are made EF (see below):
CLASSIFICATION
CODE
OBSERVATION(S) Include schedule reference, as appropriate
1-. .
.tP.,lighting, circuit at Junction
Loose connections
box.. Arcing ,and, burnt .insulation evident .........................................
as above, causing unreliable earthing
2. No additional protection bg RCD, or earthed
NOTE: Faulty section of lighting
Cl
t/‘
of circuit and risk of fire.
mechanical protection, for cables concealed in walls
....UM
circuit disconnected with Clients .approval.
One of the following codes, as appropriate, has been allocated to each of the observations made above to indicate to the person(s) responsible for
the installation the degree of urgency for remedial action.
C1 - Danger present. Risk of injury. Immediate remedial action required
02 - Potentially dangerous - urgent remedial action required
C3 - Improvement recommended
Fl - Further investigation required without delay
G u i d a n c e N o t e 3: I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
165
5
ELECTRICAL INSTALLATION
PRODUCING
1
CONDITION
REPORT NOTES FOR THE PERSON
THE REPORT
This Report should only b e used for reporting
o n the condition of an existing
electrical installation, and n o t for the replacement of a consumer u n i t /
distribution board. An installation which was designed to an earlier edition of
BS 7671 or the IEE Wiring Regulations and which does not fully comply with
the current edition is not necessarily unsafe for continued use, or requires
upgrading. Only damage, deterioration,
defects, dangerous conditions
and non-
compliance with the requirements of BS 7 6 7 1 or t h e IEE Wiring Regulations,
which may give rise t o danger, should b e recorded.
2
The Report, normally comprising at least five pages, should include schedules
of both the inspection a n d t h e test results. Additional pages may be necessary
for other than a simple installation a n d for the "Guidance for recipients". The
number of each page should b e indicated, together with the total number
pages involved.
of
3
The reason for producing this Report, such as change of occupancy or landlord's
4
Those elements of the installation that are covered by the Report and those
that are not should b e identified in Section D (Extent and limitations). These
periodic maintenance, should b e identified in Section B.
aspects should have b e e n agreed with the person ordering the report and
other interested parties before the inspection and testing commenced. Any
operational limitations, such as inability t o gain access t o parts of the installation
or an item of equipment, should also b e recorded in Section D.
5
The maximum prospective value of fault current (l p f) recorded should b e the
greater of either the prospective value of short-circuit current or the prospective
value of earth fault current.
6
Where a n installation has an alternative source of supply a further schedule of
supply characteristics and earthing arrangements based u p o n Section I of this
7
A summary of the condition of the installation in terms of safety should
b e clearly stated in Section E. Observations, if any, should b e categorized in
Report should b e provided.
Section K using the coding C l to C3 as appropriate.
Any observation given
a code C l or C 2 classification should result in the overall condition of t h e
installation being reported as unsatisfactory.
8
Wherever practicable, i t e m s classified as 'Danger p r e s e n t ' ( C l ) should b e
m a d e s a f e o n discovery. Where this is not possible the owner or user should
b e given written notification
9
as a matter of urgency.
Where an observation requires further investigation (Fl) because the inspection
has revealed an apparent deficiency which could not, owing to the extent or
limitations of the inspection, b e fully identified and further investigation may
reveal a code C l o r C2 item, this should b e recorded within Section K, given
the code Fl and marked as unsatisfactory in Section E.
10 If the space available for observations
in Section K is insufficient,
additional
pages should b e provided as necessary.
11 The
date
by
which
the
next
Electrical
Installation
Condition
Report
is
recommended should b e given i n Section F. The interval between inspections
should take into account t h e requirements of Regulation 652.1 and the overall
condition of the installation.
12 Any deficiencies
ordering the work.
166
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
with
intake
equipment
should
be reported
to the person
5
ELECTRICAL INSTALLATION C O N D I T I O N R E P O R T
GUIDANCE F O R RECIPIENTS (to b e appended t o the Report)
This Report is a n i m p o r t a n t and valuable d o c u m e n t which should b e r e t a i n e d
f o r future reference.
1
The purpose of this Condition Report is to confirm, so far as reasonably
practicable, whether or not the electrical installation is in a satisfactory condition
for continued
service (see Section E). The Report should identify any damage,
deterioration, defects and/or conditions which may give rise to danger (see
Section K).
2
This Report is only valid if accompanied by the Inspection Schedule(s) and the
Schedule(s) of Circuit Details and Test Results.
3
The person ordering the Report should have received the 'original' Report and
the inspector should have retained a duplicate.
4
The 'original' Report should b e retained in a safe place and be made available
to any person inspecting or undertaking work o n t h e electrical installation in
the future. If t h e property is vacated, this Report will provide the n e w o w n e r /
occupier with details of t h e condition of the electrical installation at the t i m e the
Report was issued.
5
Section D (Extent and Limitations) should identify fully t h e extent of the
installation covered by this Report and any limitations o n the inspection and
testing. The inspector
ordering
the
Report
should
and with
have agreed
other
these
interested
aspects with
parties
the
(licensing
person
authority,
insurance company, mortgage provider and the like) before t h e inspection was
carried out.
6
Some operational limitations such as inability to gain access to parts of t h e
installation or an item of equipment m a y have been encountered during the
inspection. The inspector should have noted these in Section D.
7
For items classified in Section K as C l ('Danger present'), t h e safety o f t h o s e
using the installation is at risk, and it is recommended that a skilled person
or persons competent
in electrical installation work undertakes the necessary
remedial work immediately.
8
For items classified in Section K as C2 ('Potentially dangerous'), the safety o f
those using the installation may b e a t risk and it is recommended that a
skilled person or persons competent
in electrical installation work undertakes
the necessary remedial work as a matter of urgency.
9
Where it has been stated in Section K that an observation requires further
investigation (code Fl) the inspection has revealed an apparent deficiency which
may result in a code C l or C2, and could not, due to the extent or limitations
of t h e inspection,
without
b e fully identified. Such observations should b e investigated
delay. A further examination
determine
of the installation
will be necessary, to
the nature and extent of the apparent deficiency (see Section F).
10 For safety reasons, t h e electrical installation should b e re-inspected at
appropriate intervals by a skilled person or persons, competent in such work.
The recommended
date by which t h e next inspection is due is stated in
Section F of the Report under 'Recommendations'.
11 Where the installation includes a residual current device (RCD) it should b e
tested
six-monthly
should
switch
by pressing the button
off the
supply
and should
marked
then
T
or 'Test'. The device
b e switched
o n to restore
the supply. If t h e device does n o t switch off t h e supply when t h e button is
pressed, seek expert advice. For safety reasons i t is i m p o r t a n t t h a t this
instruction is followed.
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineering and Technology
167
5
1 2 Where t h e installation includes an arc fault detection device
(AFDD) having
a manual test facility it should b e tested six-monthly by pressing t h e test
button. Where an AFDD has both a test button and automatic test function,
manufacturer's
instructions
shall b e followed
with
respect
to
test
button
operation.
CONDITION
1
R E P O R T INSPECTION
SCHEDULE GUIDANCE
F O R INSPECTORS
Section 1.0. Where inadequacies in t h e intake equipment are encountered t h e
inspector should advise t h e person ordering the work to inform the appropriate
authority.
2
The schedule is not exhaustive.
3
Numbers in brackets are regulation references to specified requirements.
▼ Figure 5.10 Example Condition Report Inspection Schedule (page 1)
Certificate/Report
£342
Number ....................
CONDITION REPORT INSPECTION SCHEDULE FOR
RESIDENTIAL AND SIMILAR PREMISES WITH UP TO 100 A SUPPLY
Note: This form is suitable for many types of smaller installation, not exclusively residential.
The persons responsible for the periodic inspection of the installation should include the relevant items in relation to the electrical
installation, the inspection schedule can be reduced or expanded depending on the requirements for the installation.
State Further
C3 investigation
Improvement
Unacceptable
State
condition ____ C1 or C2 recommended
Acceptable
condition
OUTCOMES
Fl Not verified
N/V Limitation
LIM Not applicable
N/A
OUTCOME
ITEM
NO
1.0
1.1
SUPPLY INTAKE EQUIPMENT (visual inspection only)
Distributor/supplier
• Service
intake equipment
Where inadequacies
are found a cross should be put
against the appropriate
item a n d a comment
made in
section K. An outcome
against a n item in section 1 . 0 ,
other t h a n access to live parts, should not be used to
cable
• Service head
• Earthing
arrangement
• Meter tails
• Metering
equipment
• Isolator (where present)
Where inadequacies in t h e intake equipment
potentially
i s strongly
Person
1.2
determine
are encountered, which may
result
ordering word / Duty
holder
notified
-Yf
Consumer's
meter
2.0
PRESENCE OF ADEQUATE ARRANGEMENTS FOR OTHER SOURCES
SUCH AS MICROGENERATORS (551 .6; 551.7)
J
tails
3.0
EARTHING / BONDING ARRANGEMENTS (411.3; Chap 54)
Presence
3.2
Presence a n d condition
3.3
Provision
and condition
of distributor’s
earthing arrangement
of earth electrode
connection
of earthing/bonding l a b e l s at all appropriate
Confirmation
Accessibility a n d condition of earthing
3.6
Confirmation
3.7
Condition
3.8
Accessibility
4.0
CONSUMER UNIT(S) / DISTRIBUTION BOARD(S)
Adequacy
Security
conductor
size (542.3;
of o t h e r protective
of working space/accessibility
of fixing
to consumer
Condition
of enclosure(s)
in terms
Condition
of enclosure(s)
in terms of fire rating
4.5
Enclosure
not damaged/deteriorated
4.6
Presence
of main
4.7
Operation
4.8
Manual
operation
4.9
Correct
identification
4.10
Presence of R C D six-monthly
switch
(functional
of circuit
Presence
of alternative supply
Presence
of other
4.13
Compatibility
required
board
(132.12;
513.1)
etc ( 4 1 6 . 2 )
etc (421.1 .201, 526.5)
impair
safety (651.2)
of protective
check) ( 6 4 3 . 1 0 )
and RCDs
to prove disconnection
details and protective
warning
labelling
notice
d e v i c e a n d base
switching
against
damage
Protection
against electromagnetic
522.8.11;
RCD(s)
provided
RCD(s)
provided for a d d i t i o n a l protection
4.19
Confirmation
for fault protection
and Technology
unit/distribution
board
N/A
N/A
(514.15)
514)
components; correct type and rating.
(No
o r o v e r h e a t i n g ) (536.4.203)
in line conductors o n l y ( 1 3 2 . 1 4 . 1 ; 5 3 0 . 3 . 2 )
where
cables
enter
consumer
effects where cables enter consumer
4.17
G u i d a n c e N o t e 3 : I n s p e c t i o n & Testing
7
(514.12.2)
unit/distribution
board (132.14.1;
530.3.2)
4.18
of indication
(Section
and other
o r protective devices
mechanical
522.8.5;
(643.10)
devices ( 5 1 4 . 8 . 1 ; 5 1 4 . 9 . 1 )
at or near consumer
(please specify)
of u n a c c e p t a b l e thermal d a m a g e , arcing
522.8.1;
© The Institution of Engineering
unit/distribution
test notice, where required
4.11
4.16
of IP rating
so a s to
of circuit-breakers
4.12
Protection
544.1.2)
l i n k e d switch ( a s required by 462.1.201)
of main
Single-pole
(543.3.2;
( 1 34.1 .1 )
4.3
4.14
(544.1)
b o n d i n g connections (543.3.2)
4.4
4.15
at M E T (543.3.2)
of m a i n protective b o n d i n g conductor connections
and condition
N/A
J
J
J
(542.1.2.3)
(514.13.1)
543.1.1)
conductor
of m a i n protective b o n d i n g conductor sizes
a n d accessibility
applicable
locations
3.4
of earthing
N/A
( 5 4 2 . 1 . 2 . 1 ; 542.1.2.2)
where
3.5
4.2
N/A (Delete
N/A
1.3
4.1
It
(Delete as appropriate)
isolator (where present)
3.1
- includes
unit/distribution
RCBOs (41 1 .4.9; 41 1 .5.2; 5 3 1 .2)
board/enclosures
y
(521 .5.1)
N/A
- i n c l u d e s RCBOs (411 ,3.3; 415.1)
that S P D is functional (651.4)
the overall outcome.
i n a dangerous o r
dangerous
situation,
the person ordering
the work and/or duty holder m u s t be informed.
recommended t h a t the person ordering the work informs t h e appropriate
authority.
Consumer's
signs
168
(Use codes above. Provide additional
comment where appropriate.
Cl, C2, C3 and Fl coded items to be recorded
in Section K of the Condition Report)
DESCRIPTION
N/A
a s appropriate)
5
▼ Figure 5.11 Example Condition Report Inspection Schedule (page 2)
Certificate/Report
OUTCOMES
Acceptable
Unacceptable
condition
condition
Improvement
State
Further
C 1 or C 2 recommended
C3
investigation
State
Fl Not verified
N/V
Limitation
1342
Number ....................
LIM
Not applicable
N/A
OUTCOME
ITEM
(Use codes above. Provide additional
comment where appropriate.
DESCRIPTION
NO
C1, C2, C3 and Fl coded items to be recorded
in Section K of the Condition Report)
4.20
that ALL conductor connections,
Confirmation
terminals and are tight and secure (526.1)
4.21
Adequate
4.22
Adequate arrangements where a generating
5.0
FINAL CIRCUITS
5.1
Identification
5.2
Cables
5.3
Condition
5.4
Non-sheathed
cables
■ To include
the integrity
5.5
Adequacy
5.6
Coordination
between
conductors
of protective
devices:
located
in
to the public supply (551 .6)
set operates as a switched alternative
where a generating
arrangements
are correctly
to busbars,
connections
including
in parallel with the public supply (551 .7)
set operates
✓
N/A
N/A
of conductors (514.3.1)
correctly
their run (522.8.5)
throughout
supported
Cl
of live parts (416.1)
of insulation
capacity with regard for the type and nature of installation
of cables for current-carrying
5.7
Adequacy
5.8
Presence a n d adequacy
appropriate
(433.1;
533.2.1)
for fault protection
(41 1 .3)
devices
protective
and overload
type and rated current
Wiring system(s)
Concealed
5.11
C a b l e s concealed under floors, above ceilings
damage (see Section D. Extent and limitations)
5.12
Provision
cables installed i n prescribed
D. Extent
z o n e s (see Section
influences
and external
for the type and nature of the installation
5.9
5.10
(Section 523)
y'
(433.1; 543.2.1)
conductors
protective
of circuit
and plastic)
(metallic
systems
and trunking
of conduit
or trunking (521.10.1)
in conduit, ducting
by enclosure
protected
adequately protected
o r in walls/partitions,
(522.6.204)
(Section 522)
(522.6.202)
and limitations)
against
of additional protection by R C D n o t exceeding 30 mA:
■ for all socket-outlets
to m o b i l e e q u i p m e n t not exceeding 32 A rating for u s e outdoors
■ for cables
concealed
sealing
of fire barriers,
and protection
arrangements
Provision
B a n d II c a b l e s segregated/separated from Band I cables (528.1)
5.15
Cables segregated/separated from communications
5.16
Cables
5.17
Termination of cables at enclosures
visible
connected at point of entry to enclosure
of accessories including
5.19
Suitability
of accessories for external influences
5.20
Adequacy of working space/accessibility
5.21
Single-pole
(526.5)
(glands,
to equipment
LOCATION(S) CONTAINING A BATH OR SHOWER
Additional
6.2
Where
used as a protective
measure,
with B S EN 61558-2-5
supply units comply
Presence
of supplementary
6.5
Low voltage
bonding
by RCD not exceeding
for SELV o r PELV met (701 .414.4.5)
for installed
location
6.6
Suitability
of equipment
6.7
Suitability
of accessories a n d controlgear etc. for a particular
6.8
Suitability
of current-using
equipment
by B S 7671:2008
(701.415.2)
sited at least 2 . 5 m from z o n e 1 (701.512.3)
influences
for particular
in terms of IP rating (701 .512.2)
the location
7.0
OTHER PART 7 SPECIAL INSTALLATIONS OR LOCATIONS
7.1
List all other special installations
applied.)
particular inspections
(701 .55)
if any. (Record separately the results of
8.0
CHAPTER 82 PROSUMER’S LOW VOLTAGE ELECTRICAL INSTALLATION(S)
8.1
and recommendations
Where the installation includes additional requirements
items should be a d d e d to the checklist.
Chapter 8 2 , additional Inspection
Inspected by: OEOFF THOMPSON
Name (Capitals) ................................
y
y
zone (701.512.3)
position within
o r locations present,
(?3
N/A
B S 3535 (701 .512.3)
formerly
unless not required
conductors,
(e.g. 2 3 0 volt) socket-outlets
for external
30 mA (701.41 1.3.3)
(LV) circuits
requirements
for all low voltage
Shaver
Cl
.y
513.1)
(132.12;
6.0
6.3
etc.) (522.8.5)
(512.2)
6.1
6.4
bushes
devices in line conductors only (132.14.1; 530.3.2)
switching o r protective
protection
Cl
switches a n d joint boxes (651.2)
socket-outlets,
Condition
526)
enclosure (526.8)
outside
5.18
D of the report (Section
in Section
strain (526.6)
■ Connections of live conductors adequately enclosed
* Adequately
y'
(528.3)
- indicate extent of sampling
made a n d under n o undue
■ No b a s i c insulation of a conductor
527)
cabling (528.2)
services
segregated/separated from non-electrical
• Connections soundly
effects (Section
thermal
against
5.13
5.14
LIM
N/A
of depth (522.6.203)
metal parts regardless
containing
( 4 11 .3.3)
522.6.203)
in walls at a depth of less than 5 0 m m (522.6.202;
■ for cables concealed in walls/partitions
y'
(411.3.3)
of rating 32 A or less, unless an exception is permitted
■ for supply
Signature
relating
to
N/A
N/A
14/OS/2O22
TpwzmjWWx
...................................... Date ....................
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
169
NOTES
170
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Appendix
A
Maximum permissible measured
earth fault loop impedance (EFLI)
Al
643.7.3
Tables
The tables in this appendix provide maximum
permissible
measured EFLI (Z s) for
411.4.201
compliance with BS 7671, which must not b e exceeded when the tests are carried
411.4.202
out at an ambient temperature of 10 °C. Table A7 provides correction factors for other
411.4.203
ambient temperatures.
Where t h e cables to b e used are to Table 3, 4 or 5 of BS 6004, Table 3, 4 o r 5 o f
BS 7211, Table B.l or B.2 of BS EN 50525-3-41 or are other thermoplastic (PVC) or
thermosetting (low smoke halogen-free - LSHF) cables to these British Standards,
and the cable loading is such that the maximum operating temperature is 70 °C, then
Tables A l to A4 give the maximum EFLIfor circuits with:
(a) protective conductors of copper and having f r o m 1 m m 2 to 16 m m 2 csa; and
(b) an overcurrent protective device (OCPD) (i.e. a fuse) to BS 3 0 3 6 , BS 88-2,
BS 88-3 or BS 1361.
For each t y p e of fuse, two tables are given:
411.3.2.2
1
where the circuit concerned is a final circuit not exceeding 32 A for circuits
supplying only fixed equipment,
or 6 3 A for circuits with one o r m o r e
socket-outlets, and the maximum disconnection t i m e for compliance with
Regulation 411.3.2.2 is 0.4 s for TN systems; and
411.3.2.3
2
where the circuit concerned is a final circuit exceeding 32 A for circuits
supplying only fixed equipment,
or 63 A for circuits with one or m o r e
socket-outlets,
or
a
distribution
circuit
and
the
disconnection
time
for
compliance with Regulation 411.3.2.3 is 5 s for TN systems.
543.1.3
In each table, the EFLI given correspond to t h e appropriate disconnection time f r o m
a comparison of the time/current characteristics of t h e device concerned and t h e
adiabatic equation given in Regulation 543.1.3.
The tabulated values apply only where the nominal voltage to Earth (U o) is 2 3 0 V.
Table A5 gives the maximum
measured Z s for circuits protected by circuit-breakers to
BS 3871-1 and BS EN 6 0 8 9 8 , and RCBOsto BS EN 61009.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
171
A
Tables 41.2 to 41.4
543.1.3
Note:
The impedances tabulated in this appendix are lower than those in Tables 41.2 to
41.4 of BS 7671. This is because the impedances in this appendix are measured
values at an assumed conductor temperature of 10 °C, whilst those in BS 7671 are
design figures at the line conductor maximum permitted operating temperature given
in Table 52.1 of BS 7671 and the protective conductor assumed initial temperature
given in Tables 54.2 to 54.5 of BS7671. The correction factor (divisor) used is 1.25.
This corresponds to the line conductor maximum operating temperature and
protective conductor assumed initial temperature both being 70 °C. For smaller csa
cables, the impedance may also be limited by the adiabatic equation of Regulation
543.1.3. A value of k of 115 from Table 54.3 of BS 7671 is used. This is suitable for
PVCinsulated and sheathed cables to Tables 3, 4 or 5 of BS6004 and forthermosetting
(LSHF) insulated and sheathed cables to Tables 3, 4 or 5 of BS 7211 or Table B.l or
B.2 of BS EN 50525-3-41 . The k value is based o n both the thermoplastic (PVC) and
thermosetting (LSHF) cables operating at a maximum temperature of 70 °C.
▼ Table Al Semi-enclosed fuses. Maximum measured EFLI (in Q) at ambient temperature
where the OCPD is a semi-enclosed fuse to BS 3 0 3 6
(i)
0.4 s disconnection (final circuits n o t exceeding 32 A for circuits supplying only
fixed equipment, or 63 A for circuits with one or more socket-outlets, in
TN systems)
Fuse rating
Protective
conductor (mm 2)
15 A
5A
20 A
30 A
(ii) 5 s disconnection (final circuits exceeding 32 A for circuits supplying only fixed
equipment, or 63 A for circuits with one or more socket-outlets, and
distribution circuits in TN systems)
Protective
conductor (mm 2)
Note:
Fuse rating
20 A
30 A
45 A
60 A ____
1.0
2.3
NP
NP
NP
1.5
2.91
1.6
NP
NP
2.5
2.91
2.0
1.0
NP
4.0
2.91
2.0
1.2
0.85
>6.0
2.91
2.0
1.2
0.85
NP means that the combination of the protective conductor and the fuse is Not
Permitted.
▼ Table A2 BS 88-2 fuses. Maximum measured EFLI (in Q) at ambient temperature where
the OCPD is a fuse to BS 88-2 or BS 8 8 - 6
(i) 0.4 s disconnection (final circuits not exceeding 32 A for circuits supplying only
fixed equipment, or 63 A for circuits with one or more socket-outlets, in
TN systems)
Protective
conductor (mm 2)
172
Fuse rating
2A
4A
6 A
10 A
16 A
20 A
25 A
32 A
1.0
26.5
12.5
6.2
3.7
1.9
1.3
1.0
0.6
1.5
26.5
12.5
6.2
3.7
1.9
1.3
1.0
0.8
>2.5
26.5
12.5
6.2
3.7
1.9
1.3
1.0
0.8
Guidance Note 3: Inspection & Testing
© T h e Institution of Engineering and Technology
(ii) 5 s disconnection (final circuits exceeding 3 2 A for circuits supplying only fixed
equipment, or 63 A for circuits with one or more socket-outlets, and distribution
circuits in TN systems)
Protective
conductor (mm 2)
Fuse rating
20 A
25 A
32 A
40 A
50 A
63 A
80 A
100 A
_________1.0 _________
1.46
1.03
0.63
0.55
NP
NP
NP
NP
1.5
2.13
1.2
0.87
0.83
NP
NP
NP
NP
2.5
2.24
1.76
1.336
1.04
0.5
0.3
NP
NP
4.0
2.24
1.76
1.364
1.04
0.76
0.49
0.22
0.12
6.0
2.24
1.76
1.36
1.04
0.79
0.62
0.3
0.19
10.0
2.24
1.76
1.36
1.04
0.79
0.62
0.44
0.32
16.0
2.24
1.7
1.36
1.04
0.79
0.62
0.44
0.34
Note:
NP means that the combination of the protectivei conductor and the fuse is Not
Permitted.
▼ Table A3 BS88-3 fuses. Maximum measured EFLI(in Q) at ambient temperature where
the OCPD is a fuse to BS 88-3
(i) 0.4 s disconnection (final circuits not exceeding 32 A for circuits supplying only
fixed equipment, or 63 A for circuits with one or more socket-outlets, in
TN systems)
Protective
conductor (mm 2)
Fuse rating
5A
16 A
20 A
32 A
1.0
7.94
1.84
1.54
0.6
1.5
7.94
1.84
1.54
0.73
2.5 to 16
7.94
1.84
1.54
0.73
(final circuits exceeding 32 A for circuits supplying only fixed
equipment, or 63 A for circuits with o n e or more socket-outlets, a n d distribution
circuits in TN systems)
(ii) 5 s disconnection
Protective
conductor (mm2 )
Note:
Fuse rating
20 A
32 A
45 A
63 A
80 A
100 A
1.0
2.13
0.59
NP
NP
NP
NP
1.5
2.57
0.76
NP
NP
NP
NP
2.5
2.57
1.13
0.55
0.24
NP
NP
4.0
2.57
1.25
0.76
0.32
0.19
NP
6.0
2.57
1.25
0.76
0.51
0.29
0.16
10.0
2.57
1.25
0.76
0.55
0.4
0.26
16.0
2.57
1.25
0.76
0.55
0.4
0.3
NP means that the combination of the protective conductor and the fuse is Not
Permitted.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
173
▼ Table A4 BS 1361 fuses. Maximum measured EFLI (in Q) at ambient temperature where
the OCPD is a fuse to BS 1361
(i) 0.4 s disconnection (final circuits n o t exceeding 32 A for circuits supplying only
fixed equipment, or 63 A for circuits with one or more socket-outlets, in
TN systems)
Protective
conductor (mm 2)
Fuse rating
5A
15 A
20 A
30 A
1.0
7.95
2.50
1.29
0.77
1.5to 16
7.95
2.50
1.29
0.86
(ii) 5 s disconnection (final circuits exceeding 32 A for circuits supplying only fixed
equipment, or 63 A for circuits with one or more socket-outlets, and distribution
circuits in TN systems)
Protective
conductor (mm 2)
Fuse rating
20 A
30 A
45 A
60 A
80 A
100 A
1.0
1.46
0.77
NP
NP
NP
NP
1.5
1.98
0.97
0.32
NP
NP
NP
2.5
2.13
1.40
0.49
0.20
NP
NP
4.0
2.13
1.40
0.67
0.35
0.20
NP
6.0
2.13
1.40
0.73
0.47
0.27
0.13
10.0
2.13
1.40
0.73
0.53
0.38
0.20
16.0
2.13
1.40
0.73
0.53
0.38
0.28
Notes:
1 NP means that the combination of the protective conductor and the fuse is Not Permitted.
2 While BS 88-3 has replaced BS 1361, and BS 1361 has been withdrawn, it can
be seen from Table A3 that the maximum measured EFLI for BS 88-3 fuses
cannot be applied to circuits protected by BS 1361 fuses, even of the same
nominal rating. For example, the maximum permitted EFLI for 20 A fuses to
BS 88-3 is far higher than that permitted for a circuit protected by a 20 A fuse to BS 1361.
174
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
A
▼
T a b l e A 5 Circuit-breakers. M a x i m u m m e a s u r e d EFLI ( i n O) at a m b i e n t t e m p e r a t u r e
w h e r e t h e o v e r c u r r e n t d e v i c e is a circuit-breaker to B S 3 8 7 1 o r B S E N 6 0 8 9 8
or RCBOto BS EN 6 1 0 0 9
For 0.1 to 5 s disconnection times (includes 0.4 s disconnection time)
Circuit-breaker rating (amps)
Circuit
breaker
type
3
5
6
10
15
16
20
25
30
32
40
45
50
63
100
1
14.56
8.74
7.28
4.4
2.93
2.76
2.2
1.76
1.47
1.38
1.1
0.98
0.88
0.7
0.44
2
8.4
5.0
4.2
2.5
1.67
1.58
1.25
1.0
0.83
0.79
0.63
0.56
0.5
0.4
0.25
B
11.65
7.0
5.82
3.5
2.33
2.15
1.75
1.4
1.17
1.1
0.87
0.78
0.7
0.55
0.35
3&C
5.82
3.49
2.91
1.75
1.16
1.10
0.87
0.7
0.58
0.54
0.44
0.38
0.35
0.28
0.18
Circuit-breakers. Maximum measured EFLI (in Q) at ambient temperature where
the overcurrent device is a circuit-breaker to BS EN 60898 type D or RCBO to
BS EN 61009 type D
Circuit
breaker type
Circuit-breaker rating (amps)
6
10
16
20
25
32
40
D 0.4 sec
1.46
0.87
0.55
0.44
0.35
0.28
-
D 5 sec
2.91
1.75
1.09
0.87
0.7
0.55
0.44
50
0.35
63
100
-
-
0.28
0.17
Regulation 434.5.2 of BS 7671 :2018 requires that the protective conductor csa meets
t h e requirements of BS EN 60898-1-2 or BS EN 61009-1, or t h e m i n i m u m quoted by
t h e manufacturer. The sizes given in Table A6 are for energy-limiting
Class 3, Types B
and C devices only.
▼
T a b l e A6 Minimum
protective
conductor
Energy-limiting
Class 3 device
rating (A)
Fault level (kA)
Up to and including
16A
size f o r Class 3 Types B a n d C devices
Protective conductor csa (mm 2) ’
Type B
Type C
< 3
1.0
1.5
Up to and including
16A
< 6
2.5
2.5
Over 16 A and up
to and including
32A
< 3
1.5
1.5
Over 16 A and u p
to and including
32 A
< 6
2.5
2.5
40 A
< 3
1.5
1.5
40 A
< 6
2.5
2.5
For other d e v i c e types and ratings, or higher fault levels, consult m a n u f a c t u r e r ' s data.
S e e Regulation 4 3 4 . 5 . 2 a n d t h e I E T Electrical
Installation
Design
Guide.
Guidance Note 3: Inspection & Testing
© The Institution of Engineeringand Technology
175
▼ T a b l e A 7 Ambient temperature correction factors
Ambient temperature (°C)
Correction factor (from 10 °C)
(Notes 1 and 2)
Notes:
1
The correction factor is given by: {1 + 0.004
(ambient
temp - 20)}/{l
+ 0.004
(10 - 20)} where 0 . 0 0 4 is t h e simplified resistance coefficient per °C at 20 °C given b y
BS EN 6 0 2 2 8 for b o t h copper a n d aluminium conductors. (Alternatively, t h e correction
factor is given by (ambient temp + 230)/(10 + 230)).
2
The factors are different f r o m those of Table B.2 because Table A7 corrects f r o m 1 0 °C
a n d Table B.2 f r o m 2 0 °C.
The ambient correction factor of Table A7 is applied to t h e EFLIof Tables A l to A5 if
t h e ambient temperature is other than 10 °C.
For example, if t h e ambient temperature is 2 5 °C, t h e measured EFLI of a circuit
protected by a 3 2 A Type B circuit-breaker to BS EN 6 0 8 9 8 should not exceed
1.1 x 1.06 = 1.17 Q .
A 2 Appendix
Anox 3
3 of B S 7671
Appendix 3 of BS 7671 takes into account t h e increase of the conductor resistance with
increase of temperature due to load current, which may b e used to verify compliance
with t h e requirements of Regulation 41 1.4 for TN systems.
The requirements
of Regulation 411 .4.4 are considered met when the measured value
of fault loop impedance satisfies the following equation:
Zs(nn)=0.8x
U X min
°j
where:
176
G u i d a n c e Note
Zs (m)
is the measured impedance of the earth fault current loop up to the most
distant point of the relevant circuit from the origin of the installation (£2)
Uq
la
is the nominal ACrms line voltage to Earth (V)
is the current in amps (A) causing operation of the protective device
within t h e time stated in Table 41.1 of BS 7671 or within 5 s according to
the conditions stated in Regulation 411.3.2.3.
Cmin
0.8
isthe minimum voltagefactorto take account of voltagevariationsdepending
o n time and place, change of transformer taps and other considerations.
is a temperature adjustment factorfor ambient temperature (see Table A7).
Note:
For an LV supply given in accordance with t h e ESQCR, C m in 's given t h e value 0.95.
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
A3
Methods of adjusting tabulated values of Z s
(See also Section 2.6.16 (EFLI verification).)
A circuit is wired in flat t w i n and cpc 70 °C thermoplastic (PVC) cable and protected
by a 6 A Type B circuit-breaker to BS EN 60898.
When tested at a n ambient
temperature
acceptable measured value of
below 20 °C, determine
the maximum
Z s for the circuit.
Solution:
Ztest ( m a x ) “
Zs
From Table 41.3(a) of BS7671, the maximum permitted value of Zs = 7.28 Q
From Table B3 in Appendix B of this Guidance Note, F = 1.20
Ztest (max) = 1 , 2 0 X
Ztest (max) = 6 . 0 7 Q
A more accurate value can b e obtained if t h e external EFLI,Ze , is known. I n this case,
the following formula may b e used:
test - Z e + |z (z s
Z e)
In the example above, assume Ze is 0.35. Thus, t h e m o r e accurate value is:
Ztest (max) = 0 . 3 5 + 1 2
-28-0.35)
Ztest (max) = 6 . 1 3 Q
Where the test ambient
temperature
is likely to b e other than 2 0 °C, a further
correction can b e m a d e to convert t h e value to correspond with the expected ambient
temperature, using the following formula:
Ztest (max) = 2 e +
Z e)
where a is given by Table B2 of Appendix B.
In the example above, assume the test ambient temperature
is 5 °C.
From Table B2, a = 0.94
Thus, the accurate reading including temperature
Ztest(max)= 0 . 3 5 +
Aest
compensation
is:
(7.28-0.35)
(max) = 5 . 7 8 Q
Guidance Note 3 : Inspection & Testing
© T h e Institution of Engineering and Technology
177
Note:
Where reduced csa protective conductors are used, maximum EFLIsmay need to
be further reduced to ensure disconnection times are sufficiently short to prevent
overheating of protective conductors during earth faults. The requirement of the
equation in Regulation 543.1.3 needs to be met:
where:
S
k
I
Zs
t
Note:
is the nominal csa of the conductor in m m 2
means greaterthan or equal to
is a factor taking account of the resistivity, temperature coefficient and
heat capacity of the conductor material and the appropriate initial and final
temperatures; see Tables 54.2-54.4
is the value in amps (rms for AC) of fault current for a fault of negligible
impedance, which can flow through the associated protective device, d u e
account being taken of the current-limiting effect of the circuit impedances
and the limiting capability (12 t) of that protective device
is the loop impedance at conductor normal operating temperature
is the operating t i m e of the overcurrent device in s corresponding to t h e
fault current I a m p s - obtained from the graphs in Appendix 3 of BS7671,
as the prospective earth fault current I (= U q X Cm jn /Z s) is known.
Cm in is the minimum voltage factor, the meaning of which is explained in Section A2
of this appendix.
The following example illustrates h o w measurements taken at 2 0 °C may b e adjusted
to 70 °C values, taking t h e (R] + R2) reading for t h e circuit into account.
In the previous example, taking t h e (Ri + R2) reading for t h e circuit as 0.2 Q :
Z s for t h e circuit at 70 °C
= Ze +F(R 1 + R 2)test
= 0.35+1.20x0.2
= 0.59 Q
The temperature-corrected Z s figure of 0.59 Q is acceptable, as it is less than t h e
maximum value of 7.28 Q given in Table 41.3 of BS 7671.
The formula above involves taking measurements at 2 0 °C and converting t h e m to
70 °C values. Alternatively, t h e 70 °C values can b e converted to t h e values at t h e
expected ambient temperature, for example, 20 °C, when the measurement is carried out.
178
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineeringand Technology
I A
Taking t h e same circuit:
Ztest
= Ze + ( R i + Rz)test
= 0.32+0.2
= 0.55Q
From the formula: Z test ( m a x ) = p Z s Z s (m a x) f r o m B S 7 6 7 1 = 7.28 Q
Ztest(max) = 1,20
x
7.28=6.07£2
Therefore, as 0.55 Q is less than 6.07 Q, t h e circuit is acceptable.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
179
NOTES
180
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution
of Engineering and Technology
Appendix
B
Resistance of copper and
aluminium conductors
434.5.2 To check compliance with Regulation 434.5.2 and/or Regulation 543.1.3, i.e. to evaluate
543.1.3 the equation
I2!
S2 = 1,2
it is necessary to establish the impedances of the circuit conductors to determine the
fault current, I, and hence the protective device disconnection
Fault current, I =
time, t.
Un
x
0
where:
Uo
Cmin
is the nominal voltage to Earth
is the minimum voltage factor to take account of voltage variations
depending o n time and place, changing of transformer taps and other
considerations
Note:
F o r LV supplies given in a c c o r d a n c e with t h e E S Q C R , C m in i s g i v e n the
value 0 . 9 5 .
Zs
is the EFLI,and
Zs = Ze + Ri + R2
where:
Ze
is that part of the EFLI external t o the installation
Note:
If t h e distribution
replaced
board
i s not
in the a b o v e equation
a t t h e origin
of the installation,
Ze is
b y Z d b . t h a t p a r t o f t h e E F L I o n the
s u p p l y s i d e of t h e d i s t r i b u t i o n b o a r d .
Ri
is
r2
is
the resistance of the line conductor from the origin of the circuit
to the point of utilization
the resistance of the protective conductor from the origin of the
circuit to the point of utilization.
Similarly, in order to design circuits for compliance with the limiting values of EFLIgiven
in Tables 41.2 to 41.4 of BS7671, it is necessary to establish the relevant impedances
of the circuit conductors w h e n the line conductor is at t h e appropriate maximum
permitted
operating temperature,
as given in Table 52.1 of BS7671, and the cpc is at
t h e appropriate 'assumed initial temperature', as given in Tables 54.2 to 54.5.
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
181
B
Table B l gives values of ( R i + R2) p e r m e t r e f o r various c o m b i n a t i o n s of c o n d u c t o r s u p
to a n d including 5 0 m m 2 csa. It also gives values of resistance in m i l l i o h m s p e r metre
for e a c h size of conductor. These values are a t 20 °C.
V
Table B l Values of resistance/metre
for copper and aluminium conductors and of
( R i + R2) Pe r metre at 20 °C in mQ/m
csa (mm 2)
182
Resistance/metre or
(R 1 + R2 )/metre (mQ/m)
Line conductor
Protective
conductor
Copper
1
—
18.10
1*
1
36.20
1.5
—
12.10
1.5*
1
30.20
1.5
1.5
24.20
2.5
—
7.41
2.5
1
25.51
2.5*
1.5
19.51
2.5
2.5
14.82
4
—
4.61
4*
1.5
16.71
4
2.5
12.02
4
4
9.22
6
—
3.08
6*
2.5
10.49
6
4
7.69
6
6
6.16
10
—
1.83
10*
4
6.44
10
6
4.91
10
10
3.66
16
—
1.15
1.91
16*
6
4.23
—
16
10
2.98
—
16
__________16
2.30
3.82
25
—
0.727
1.20
25
10
2.557
—
25
16
1.877
3.11
25
25
1.454
2.40
35
—
0.524
0.87
35
16
1.674
2.78
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
Aluminium
csa (mm 2)
Line conductor
Note:
Resistance/metre or
(Ri + R2 )/metre (mQ/m)
Aluminium
Copper
Protective
conductor
* identifies copper line/protective conductor combination that complies with Tables
4 and 5 of BS 6004:201 2+A1:2020 for thermoplastic insulated and sheathed cables,
single-core and cpc (UK code 6241Y), twin and cpc (UK code 6242Y) or three-core
and cpc (UK code 6243Y) and similar cable constructions for thermosetting cables
according to Table 5 of BS 7211:2012+AI:2020 (UK codes 6241B, 6242B, 6243B).
▼ Table B2 Ambient temperature multipliers (a) to Table Bl
| Expected ambient temperature
1
Correction factor 1 _________1
(°C)
The correction factor is given by: {1 + 0.004 (ambient temp - 2 0 °C)} where 0.004 is
the simplified resistance coefficient per °C at 20 °C given by BS EN 60228 for copper
and aluminium conductors.
To assist a n y o n e using Table B l , t h e following two f o r m u l a e m a y b e helpful:
mft/mxL
1000
L=
Rxiooo
m&/m
For verification
purposes, the designer will need to give t h e values o f the line a n d
cpc resistances a t the ambient
temperature
expected
d u r i n g t h e tests. This m a y b e
different f r o m t h e reference t e m p e r a t u r e of 2 0 ° C u s e d for Table B l . T h e correction
factors in Table B2 m a y b e applied to the Table Bl
values to take
account of the
a m b i e n t t e m p e r a t u r e (for test p u r p o s e s only).
Bl
Standard overcurrent devices
Table 41.2
Table B 3 gives the multipliers
Table 41.3
Table 41.4
p u r p o s e of calculating t h e resistance a t m a x i m u m operating t e m p e r a t u r e of t h e line
to b e applied to t h e values given in Table Bl f o r the
conductors and/or cpcs in order to determine
compliance with the EFLIof Tables 41.2,
41.3 o r 41.4 of B S 7 6 7 1 .
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and Technology
183
B
▼ Table B3 Conductor temperature factor Ffor standard devices
Multipliers
t o b e applied t o Table B l f o r devices in Tables 41.2, 41.3, 41.4
Conductor installation
Table 54.2
Table 54
Conductor insulation
70 °C
thermoplastic
(PVC)
85 °C
thermosetting
(Note 4)
90 °C
thermosetting
(Note 4)
Not incorporated in a cable and
not bunched (Notes 1,3)
1.04
1.04
1.04
Incorporated in a cable or
bunched (Notes 2, 3)
1.20
1.26
1.28
No,es:
1
2
3
4
See Table 54.2 of BS 7671. These factors apply when the protective conductor is not
incorporated or bunched with cables, or for separate bare protective conductors in
contact with cable covering but not bunched with cables.
See Table 54.3 of BS 7671. These factors apply when the protective conductor is a core
in a cable or is bunched with cables.
The factors are given by F = 1 + 0.004 {conductor operating temperature - 2 0 °C}
where 0.004 is the simplified resistance coefficient per °C at 20 °C given in BSEN 60228
for copper and aluminium conductors.
If cable loading is such that the maximum operating temperature is 70 °C, thermoplastic
(70 °C) factors are appropriate.
GN6
B2
Steel wire armour (SWA), steel conduit and steel
trunking
Formulae for t h e calculation of t h e resistance and inductive reactance values of t h e
SWA of cables and of steel conduit, ducting and trunking are published in Guidance
Note 6.
Generally, it is accepted that there is approximately a 10 °C difference between t h e
conductor temperature and the outer sheath temperature for an SWA cable at full load.
BS
GN1
184
Mineral-insulated
copper-sheathed cable
See also t h e guidance i n the appendices of Guidance Note 1 for mineral-insulated
copper-sheathed cable temperature data.
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
Appendix
C
Use of an earth leakage current
clamp meter to provide an indication
of the state of insulation
Where safe access is available to enclose the live conductors
in a current clamp,
but not t h e protective conductor, a suitably rated earth leakage current clamp meter
(sometimes called a tong tester) can b e used to provide an indication of t h e state of
insulation in a circuit downstream of the test point, by measuring 'earth leakage'. An
example is shown i n Figure C l .
In small installations, readings of a few milliamps will indicate protective conductor
currents, but readings of many amps may indicate a line-to-earth or neutral-to-earth fault.
▼ Figure Cl Example of the measurement of earth leakage with a current clamp meter
RRTE I
00D4 ISHHhWH
0101
-a-+ssx
Note:
The earth leakage current clamp for this test goes around the live conductors only.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
185
NOTES
186
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
Appendix
D
Safety check for diverted
neutral currents
DI
Dangers associated with diverted neutral currents
Diverted neutral currents can occur if there is a break i n the protective earth and
neutral (PEN) conductor in the distribution network supplying an installation with
a PME earthing arrangement. Diverted neutral currents can cause hazardous touch
voltages on the protective
earthing
system in an installation,
including
the main
earthing terminal, extraneous-conductive-parts, circuit protective conductors, and
exposed-conductive-parts.
Installations that might b e affected by diverted neutral currents include:
(a) installations in which PME conditions apply (TN-C-S earthing arrangement f r o m
a public distribution
network); and
(b) installations with TN-S or TT earthing arrangements, that share extraneousconductive-parts with installations in which PME conditions apply.
Precautions should b e taken before working o n any installation to determine
if any
hazardous touch voltages exist o n conductive parts. This is particularly important when
working outdoors and in contact with t h e general mass of Earth. Precautions should
also b e taken before disconnecting
any earthing or protective bonding conductors.
Note:
Diverted neutral currents may originate from another installation, and so may be
present even if the installation is isolated.
D2
How to check for diverted neutral currents
There is n o simple test that will indicate the presence of diverted neutral currents.
However, some simple checks can b e made with voltage indicators, non-contact
voltage testers, and earth leakage current clamp ammeters, along with an external EFLI
test. An example of an approach that could b e used in dwellings is shown in Table D I .
If an open-ciruit PEN conductor or diverted neutral currents are suspected after carrying
out the safety checks, the DNO should b e informed immediately using the emergency
number 105.
Notes:
1
2
If there is an open-circuit PEN conductor, the line to neutral voltage may rise to 400 V
nominal.
One way of measuring earth leakage is to use a leakage current clamp ammeter.
Leakage current clamp meters are similar to those used for measuring load current, but
are more sensitive and therefore more accurate at measuring currents below 5 mA.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
187
The installation may import or export diverted neutral current. Exported neutral current
occurs where there is a broken PEN conductor in the supply cable to the installation,
so neutral current finds its way back to the supply transformer through extraneousconductive-parts shared with other installations that have an intact PEN conductor.
Imported neutral current occurs where neutral currents f r o m another installation are
exporting neutral current, and these are returning to the supply transformer through
the PEN conductor of t h e installation concerned, via extraneous-conductive-parts.
▼ Table D I Example of checks for diverted neutral currents or broken PEN conductor in a
dwelling
Step
Action
Expected result
Possible indication
of diverted neutral
currents or a
broken PEN
conductor
1.
Before isolating t h e
installation, measure the
current flowing i n t h e m a i n
earthing conductor and m a i n
protective bonding
conductors of t h e installation
using a current clamp meter.
A small current will b e
expected, when compared
with line conductor currents.
In dwellings, a n d similar
installations with a m a x i m u m
d e m a n d of u p to 100 A, this
is typically a few milliamps.
Large currents flowing
i n the earthing
conductor a n d / o r
main bonding
conductors.
2.
Switch off power to the
installation, lock-off or
otherwise secure t h e point(s)
of isolation, a n d prove the
installation is dead using an
approved 2-pole contact
voltage tester.
The test for proving that t h e
installation is dead shows it
is dead.
The installation does
not appear to b e dead
as expected.
3.
Check for current flowing i n
the m a i n earthing conductor
a n d m a i n protective bonding
conductors of t h e installation
using a current clamp meter.
The current has dropped to
zero, or to an extremely small
level.
Current continues to
flow i n t h e
earthing conductor
and/or main bonding
conductors. Current
measured in t h e
customer
bonding conductors
orpipework can b e
influenced by adding
load to the
customers installation,
using a simple
technique such as
boiling a kettle or
switching a heater on.
4.
188
Check for t h e presence of
voltage using a non-contact
voltage detector at the main
earthing terminal, along the
length of t h e m a i n earthing
conductor, m a i n protective
bonding conductors, and a t
extraneous-conductive-parts.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
No voltage is indicated.
Voltage appears to
b e present. Voltage
indicators do not
detect diverted
neutral currents
while i t i s able
to flow using a n
alternative p a t h . A
volt-stick should
a l s o b e used.
D
5.
Disconnect t h e main
protective bonding
conductors.
Nothing unusual is noted.
Evidence of current
flow when the main
protective
bonding conductors
are disconnected.
6.
Re-check for t h e presence o f
voltage using a non-contact
voltage detector at t h e m a i n
earthing terminal, along t h e
length of t h e m a i n earthing
conductor, m a i n protective
bonding conductors, and at
extraneous-conductive-parts.
No voltage is indicated.
Voltage appears to
b e present. Voltage
Re-connect the main
protective bonding
conductors so that
insulation resistance tests
can be carried out.
Nothing unusual is noted.
Evidence of current
flow when the main
protective bonding
conductors is
connected.
In TN systems, during the
course of inspection and
testing, check the external
EFLI.
External EFLI measurement
appears t o b e acceptable.
The following is a rule o f
thumb, b u t occasionally
slightly higher readings m a y
b e experienced:
External EFLI is high,
8.
indicators do not
detect diverted
neutral currents
while it is able
to flow using an
alternative path. A
volt-stick should
also be used.
i n TN-C-S systems,
Ze < 0 . 3 5 Q
i n TN-S systems,
Z e < 0.80 Q
A check against previous
readings, w h e r e available,
w o u l d provide m o r e accurate
information.
Guidance Note 3: Inspection & Testing
© The Institution of Engineering and Technology
189
NOTES
190
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Index
A
Access
Accuracy of test instruments
2.5.2 item o
4.2
Additional protection
2.5.2 item h; 2.6.19
Additions and Alterations
1.4; 3.2; Section 5
Alternative supplies
warning notices
Arc fault detection devices (AFDDs)
testing
Automatic disconnection of supply (ADS)
3.9.1
2.5.2 item p
2.5.2 item I; 2.5.2 item p
5.4
2.6.14; 3.9.1
B
Barriers
fire
protection by, during erection
Basic protection
Breaking capacity of devices
2.5.2 item g
2.6.4
2.5.2 item h
Table 2.16; 2.6.17;
Section 5 Schedule of Test Results
British Standards referenced
Degrees of protection
BS EN 60529
2.5.3 enclosures
Emergency lighting
BS5266
Preface; Table 3.2 note 3
Fire alarms
BS5839
Residual current devices
B S E N 61008, 61009
Preface; 2.5.3 General item k;
2.5.3 Flexible cables item h;
Table 3.2 note 5
Table 2.6; Table 2.17
2.5.3 Switchgear item a;
2.6.16; 2.6.18; Table 2.6;
Table 2.17; Appendix A
Guidance Note 3 : Inspection & Testing
© The Institution of Engineering and T echnology
191
Index
Switchgear
B S E N 60947
2.5.2 item j; Table 2.7;
2.5.3 Switchgear item a
C
Cables
routing
2.5.2 item c
couplers
2.5.2 item f
4.2
Calibration (checking of accuracy)
Certificate, Electrical Installation
Client
1.3.1; 1.4; 1.6; 2.1; 2.2; 2.6.2; 2.6.16;
3.4; 3.8.2; 3.8.3; Section 5
Introduction; 1.1; 1.3; 1.6; 3.4; 3.6;
3.8;Table 3.3; 3.11;Section 5
Colour coding (identification
of conductors)
2.5.2 item b; 2.5.2 item p; 3.9.1
1.2; 4.9
Competence
Condition Report, Electrical Installation
1.3.1; 1.3.2; 1.6; 2.6.16; 3.1; 3.8;
3.11:3.12; Section 5
Conductors
classes
2.5.2 item a
identification
2.5.2 item b
Appx B
resistance
Construction (Design and Management)
Regulations 2015
Connection
Introduction;
1.1; 1.3.3; 1.6; 3.4;
Section 5
2.5.2 item a
of conductors
Continuity
main bonding
protective conductors
2.5.1; Section 5 ; Table 3.4
2.5.2 items b and h; 2.5.3; 2.6;
Table 3.4; 3.10.3; 4.3; Appendix A
’all-insulated' installations 2.6.5; Fig 2.5
test method 1
metallic enclosures as protective
conductors
2.6.5
test procedure
ring final circuit conductors, test method
supplementary bonding
2.6.4; 2.6.6; Fig 2.2; Fig 2.3
2.5.2; 2.6.4; 2.6.5; 2.6.1 8;3.7;
3.9.1; Table 3.4; 2.2
D
Defects
Designer
192
3.7; 3.11; Section 5
Introduction;
1.5; 2.1; 2.2; 2.5;
3.4; Section 5
Diagrams, presence of
2.5.2 item p; 3.9.1
Distribution equipment
2.9.1
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
Index
Diversity factor
Diverted neutral currents
2.5.3
3.3.3; Appx D
E
Earth electrode resistance
Earth electrode resistance testers
2.6.4; 2.6.13; Table 3.4; Fig 2.28;
Fig 2.29; Fig 2.30
2.6.13; 4.6
Earth fault loop impedance
maximum measured values
Appx A
PEIs
temperature correction
test method
Appx A
Section 2; 2.6.13
4.5
testers
verification
Earth-leakage current testing
Electrical Installation Certificate (EIC)
Electrical Installation Condition Report (EICR)
2.6.15
2.6; Appx C
1.3.1; 1.4; 1.6; 2.1 ; 2.2; 2.6.2;
2.6.16; 3.4; 3.8; Section 5
1.3.2; 3.1 1 ; 5.4
Electrical separation
insulation resistance tests
2.6.9
source of supply
inspection
2.6.9
measurement of voltage
2.6.9
Electricity at Work Regulations 1989
Preface; 1.1 ;2.1;Table 3.2 note 2;
3.3; 3.4; 3.5; 4.9
Electromagnetic disturbances
2.5.3; 2.6.23
Electronic equipment
2.6.4; 2.6.7
Electricity Safety, Quality and Continuity
Regulations
Escape routes
Table 3.2 note 1
2.5.2 item c; 2.5.3
F
Fault protection
2.5.2 item h
Fire barriers, provision of
2.5.2 item g
Fire protection
Forms
Functional extra-low voltage (FELV)
Functional testing
2.5.2 item c; 2.5.2 item d; 2.5.3
Section 5
Table 2.9; 2.6.10
2.6.4; 2.6.19; Table 3.4; 3.10.3
G
General requirements
Section 1
Guidance N o t e 3: Inspection & Testing
© The Institution of Engineering and Technology
193
Index
H
Health
a n d S a f e t y a t W o r k etc.
Act
Introduction;
1974
Health
a n d Safety
Note
Executive
2.3;
Guidance
1.1; 4.1
G S 38
1.3.2
H o u s i n g ( S c o t l a n d ) Act 2 0 1 4
Higher
3.4
risk residential b u i l d i n g s
(HRRBs)
2.5.2
item
1
I d e n t i f i c a t i o n by c o l o u r
2.5.2
item
b
I
2.3; 3.6
I n f o r m a t i o n for i n s p e c t o r
Initial i n s p e c t i o n
general
2.5.1
procedure
inspection
checklist
2.5.3
inspection
items
2.5.2
Section 5
schedule
2.6
Initial t e s t i n g
results,
2.6.1
r e c o r d i n g of
2.6.4
test sequence
Section
2
certificates
2.2; Section
5
f r e q u e n c y of s u b s e q u e n t i n s p e c t i o n
2.4; Table 3 . 2
Initial
verification
i n f o r m a t i o n for inspector
2.3
p u r p o s e of
2.1
relevant
2.1
criteria
2.4
scope
typical
Section 5
forms
Inspection checklist
2.5.3
Inspection Schedule
Section 5
Inspector's
1.2; 3.8.1
competence
1.1; Section
Instruments
I n s u l a t i o n resistance
2.6.7;
3.10.3b;
Tables
4
2.9 to 2.13
4 . 4 ; Appx
Insulation resistance testers
C
2.6.24
Inverters
J,K, L
L a b e l l i n g and
L a n d l o r d a n d Tenant
194
G u i d a n c e Note
2.5.2
marking
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
Act
1985
items
m, p; 3.9.1
1.3.2; Table 3 . 2 note
10
Index
M
1.7; 2.5.2 item h; 2.6; 3.7; Table 3 . 2
Medical locations
M i n o r Electrical I n s t a l l a t i o n W o r k s
2.2; 5 . 2 ; 5 . 4
C e r t i f i c a t e (MEIWC)
Mobile
a n d t r a n s p o r t a b l e units
Model
forms
Motor
circuits
3.7
2.2; 2.6.3;
Section 5
3.10.3 item a
N
2.6.11
Non-conducting location
2.5.2 item p
Non-standard colours
Notices
2.5.2 item p; 3.9.1
(also signs)
O
Ohmmeters
2.6.7;
i n s u l a t i o n resistance
2.6.5; 2 . 6 . 6 ; 4 . 3
low-resistance
Older
installations,
inspection
3.8.1; 3.12
of
Introduction
Operational manual
Overvoltages
4.4
2.6.21
due to faults
O v e r v o l t a g e s of a t m o s p h e r i c origin o r
2.6.22
d u e to switching
P
PELV
Periodic
2.5.2 item h; Table 2.9; 2.6.4; 2.6.8;
Table 2.12; Table 2.13; 2.6.10; 3.9.1; 4.4
inspection
general procedure
3.8.2
i n s p e c t i o n checklist
3.9.1
3.1
p u r p o s e of
1.3.1; 3.11; 5.3
report
3.8.3; Table 3.3
sampling
3.8.1
visual inspection
Periodic
i n s p e c t i o n a n d testing
Section 5
forms
3.7;Table 3 . 2
f r e q u e n c y of
3.8.2; 3.8.3
general p r o c e d u r e
general requirements
information
for inspector
inspector's
competence
Section
1; Table 3.1
3.6
1.2; 3.8.1
3.2
necessity for
3.1; 3.8.1
p u r p o s e of
G u i d a n c e Note
© The Institution
3: I n s p e c t i o n & Testing
of Engineering
a n d Technology
195
Index
1.5
record keeping
requirement
3.2; 3.8.1
for
checks
3.5; Table 3.1; Table 3 . 2
Periodic testing
3.10; Table 3 . 4
Phase s e q u e n c e
2 . 6 . 4 ; 2.6.17
routine
4.8
instruments
verification
2.6.17
of
2.5.2 item e; 2.6.12; 3.10.3c;
Polarity
Table 3 . 4
2.6.12; Fig 2.27
test m e t h o d
P o w e r c o n v e r s i o n e q u i p m e n t (PCE)
2.6.24
Prospective fault current
2.6.16
Prosumers
e l e c t r i c a l installations
2.6.24
(PEIs)
P r o t e c t i o n by
barriers p r o v i d e d d u r i n g e r e c t i o n
2.6.4
enclosures
2.6.4
Protective
p r o v i d e d d u r i n g erection
multiple
2.5.2 item h; 3 . 3 . 3
e a r t h i n g (PME)
Q,R
Record k e e p i n g
1.6; 2.5.1
Reference tests
continuity
of protective
metallic enclosures
conductors
2.6.4;
2.6.5; Fig 2.1 ; Fig 2.2;
Table 3.4; 3.10.3a
a s protective
2.6.5
conductors
2.6.5
test m e t h o d s 1 a n d 2
continuity
of r i n g f i n a l circuit
conductors
2.6.6; Fig 2.2; Fig 2.19; Fig 2.20; Table 3.4
insulation
resistance test
2.6.7;
3.10.3b
resistance o f f l o o r s a n d w a l l s
2.6.11
s e q u e n c e of
2.6.4
Relevant criteria
2.1
Rented
accommodation
R e p o r t , Electrical I n s t a l l a t i o n Condition
1.3.2; 3.7
1.3.1; 1.3.2; 3.11; Section
5
Residual c u r r e n t d e v i c e s (RCDs)
f o r a d d i t i o n a l protection
2.5.2 item h
notice
2.5.2 item p
test method
testers
R e s i s t a n c e of c o n d u c t o r s
Routine checks
196
G u i d a n c e Note
3 : I n s p e c t i o n & Testing
© The Institution of Engineering and Technology
2.6.18; Table 2.17; Table 3.4
4.7
Appx B
3 . 5 ; Table 3.1; Table 3.2
Index
Routing of cables
2.5.2 item c
Rule of thumb
earth fault loop impedance
2.6.15
3-phase prospective fault current
2.6.16
S
Safety during testing
Sampling
Schedule of Circuit Details
1.1;2.6.15; 3.3.2; 3.8.2
3.8.3;Table 3.3
5.4
Schedule of Inspections
1 .3.1 ; 2.6.2; 5.1; 5.3
Schedule of Test Results
1.3.1; 2.6.2; 5.1; 5.4
SELV
2.5.1; 2.5.2 item c; 2.5.2 item h ;
2.6.4; 2.6.8; Table 2.12;
Table 2.13; 2.6.10; 3.9.1; 4.4
Separation of circuits
2.5.2 item h; 2.6.4; 2.6.8; 2.6.9
Shock hazards
1.1
Signs see Notices
Socket outlets
Specialized systems
Specification
Surge protection devices (SPDs)
Surveying, thermographic
2.5.3
1.7; 2.5.2 item h
Introduction
2.5.2 item 1;2.5.2 item p
4.9
T
Terminal connections
2.5.2 item a
Test instruments
1.1; Section 4
Thermal effects
2.5.2 items g, n; 3.9.1
Thermographic equipment
4.9
U
Utilization categories, switchgear
2.5.2 item j; Table 2.7
V
Verification, initial
Voltage drop, verification
Section 2
2.6.4; 2.6.20; 4.5
W
Working at height
1.1
X,Y, Z
No entries
Guidance N o t e 3 : Inspection & Testing
© The Institution of Engineeringand Technology
197
W r i t t e n b y industry e x p e r t s a t t h e IET (directly involved
w i t h developments
to B S 7671) and peer-reviewed by
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the IET Guidance N o t e s series comprises eight
b o o k s t h a t e x p a n d upon and simplify essential p a r t s of
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The Guidance N o t e s series has n o w been u p d a t e d
t o BS7671:2O18+A2:2O22.
Other books in t h i s series include:
Guidance Note 1 Selection & Erection
Guidance Note 2 Isolation & Switching
Guidance Note 4 Protection
Against Fire
Guidance N o t e 5 Protection Against Electric Shock
Guidance N o t e 6 Protection Against Overcurrent
Guidance N o t e 7 Special Locations
Guidance Note 8 Earthing & Bonding
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