Table Of ContentPractical Guide to Inspection, Testing and Certification of
Electrical Installations
This page intentionally left blank
Practical Guide to
Inspection, Testing
and Certification of
Electrical Installations
Conforms to IEE Wiring
Regulations/BS 7671/Part P of
Building Regulations
Christopher Kitcher
AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD
PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
Newnes is an imprint of Elsevier
Newnes is an imprint of Elsevier
Linacre House, Jordan Hill, Oxford OX2 8DP, UK
30 Corporate Drive, Suite 400, Burlington, MA 01803, USA
First edition 2008
Copyright © 2008, Christopher Kitcher. Published by Elsevier Ltd. All rights reserved
The right of Christopher Kitcher to be identified as the author of this work has been asserted in
accordance with the Copyright, Designs and Patents Act 1988
No part of this publication may be reproduced, stored in a retrieval system or transmitted in
any form or by any means electronic, mechanical, photocopying, recording or otherwise
without the prior written permission of the publisher
Permissions may be sought directly from Elsevier’s Science & Technology Rights
Department in Oxford, UK: phone (⫹44) (0) 1865 843830; fax (⫹44) (0) 1865 853333;
email:
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xi
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xiii
1. Inspection and testing of electrical installations . . . . . . . . . . . . . . . . . . .1
Why inspect and test? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Section 1. Design, Installation, Inspection and Testing . . . . . . . . . . . . .2
Section 2. Extensions, Material alterations and material
changes of use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Section 3. Information about other legislation . . . . . . . . . . . . . . . . . . .3
Compliance with Building Regulations Part P . . . . . . . . . . . . . . . . . . . . . .4
Earthing and bonding to comply with Part P . . . . . . . . . . . . . . . . . . . . . . .5
Registered domestic installer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Unregistered competent person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
DIY installer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2. Types of certification required for inspecting and testing
of installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Certification required for domestic installations (Part P) . . . . . . . . . . . . . .9
Minor Electrical Installation Works Certificate . . . . . . . . . . . . . . . . . . .9
Part P, Domestic Electrical Installation Certificate . . . . . . . . . . . . . . . . .9
Periodic inspection, testing and reporting . . . . . . . . . . . . . . . . . . . . .10
Certification required for the inspecting and testing of
installations other than domestic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Minor Electrical Installation Works Certificate . . . . . . . . . . . . . . . . . .11
Electrical Installation Certificate . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Initial verification inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Initial verification testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Periodic inspection report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Periodic inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Three phase circuit/systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Periodic testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Voltage drop in conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Contents
vi
3. Testing of electrical installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Safe isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Isolation procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Testing for continuity of protective conductors . . . . . . . . . . . . . . . . . . . .31
Main equipotential bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Continuity of supplementary bonding . . . . . . . . . . . . . . . . . . . . . . . .35
Continuity of circuit protective conductors . . . . . . . . . . . . . . . . . . . .40
Method one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Method two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Ring final circuit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Complete ring circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Broken ring circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Interconnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Performing the test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Insulation resistance test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Testing a whole installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Testing of individual circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Testing of 3 phase installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Testing of site applied insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
Polarity tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
Polarity test on a radial circuit such as a cooker or
immersion heater circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63
Polarity test on a lighting circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
Live polarity test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Earth electrode testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Earth fault loop impedance tester . . . . . . . . . . . . . . . . . . . . . . . . . . . .70
Measurement using an earth electrode test instrument . . . . . . . . . . . .72
Earth fault loop impedance Ze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Earth fault path for a TT system . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
Earth fault path for a TNS system . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
Earth fault path for a TNCS system . . . . . . . . . . . . . . . . . . . . . . . . . . .76
Circuit earth fault loop impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
Method one . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
Method two . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83
Prospective fault current test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92
Functional testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Residual current device (RCD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Types of RCD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
RCDs and supply systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
Testing of RCDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Contents
vii
4. Completion of test certificates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
Minor Electrical Installation Works Certificate . . . . . . . . . . . . . . . . . . .109
Electrical Installation Certificate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
Schedule of Circuit Details and Test Results . . . . . . . . . . . . . . . . . . . . .121
Schedule of Items Inspected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
Method of protection against electric shock . . . . . . . . . . . . . . . . . . .130
Cables and conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
Periodic Inspection Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136
Completing the form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
Summary of the inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
Overall assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
Supply characteristics, earthing and bonding arrangements . . . . . . .143
Characteristics of the supply protective device . . . . . . . . . . . . . . . . .143
Means of earthing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
Main protective conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .144
5. Safety in electrical testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
Correct selection of protective devices . . . . . . . . . . . . . . . . . . . . . . . . .149
Test equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156
Instruments required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
Calibration of test instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
Electric shock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Testing transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Testing a 3 phase induction motor . . . . . . . . . . . . . . . . . . . . . . . . . . . .164
Appendix A IP codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167
Appendix B Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
Appendix C Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175
Appendix D Answers to Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
Appendix E Answers to Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
Appendix F Useful information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
This page intentionally left blank
Preface
Part P of the Building Regulations came into effect on the 1st of January 2005.
This part of the Building Regulations requires that all electrical work carried
out in domestic installations now has to be certificated. For work places, the
Electricity at Work Regulations 1989 require that they provide a safe and well
maintained electrical system. Certification and well kept records are a perfect
way to confirm that every effort has been made to ensure that the system is,
and remains safe.
I have written this book to assist electricians of all levels in carrying out the
inspecting, testing and certification of all types of electrical installations. It will
also be invaluable to City and Guilds 2330 level 2 and 3 students, electricians
studying for City and Guilds 2391 parts 101 and 102 and all tradesmen who
are required to comply with Building Regulation part P.
Step by step guidance and advice is given on how to carry out a detailed visual
inspection during initial verifications, periodic inspections and certification.
Text and colour photographs of real, not simulated installations, are used to
show the correct test instruments. Step by step instructions for how to carry
out each test safely using different types of instruments are given along with
an explanation as to why the tests are required.
In some photographs safety signs have been omitted for clarity. All test leads
are to GS 38 where required. Some comments within this book are my own
view and have been included to add a common sense approach to inspecting
and testing.
Interpretation of test results is a vital part of the testing process. The correct
selection and use of tables from BS 7671 and the On Site Guide are shown
clearly. Any calculations required for correct interpretation or for the passing
of exams are set out very simply. An in depth knowledge of maths is not
required.
