Practical Guide to Inspection, Ttsring and Certification
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--I Practical Guide to Inspection, Ttsring and Certification D L i Practical Guide to Inspection, Testing and Certification of ~ Electrical Installations Conforms to IEE Wiring Regulations/BS 7671/Part P of B u i Id i ng Regu Iat ions Christopher Kitcher AMSTERDAM BOSTON HEIDELBERG LONDON NEWYORK OXFORD PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO ELSEVIER Newnes is an imprint of Elsevier Newnes 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 0 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: [email protected]. Alternatively you can submit your request online by visiting the Elsevier web site at http://eIsevier.com/locate/permissions, and selecting Obtaining permission to use Elsevier material Notice No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Disclaimer This book draws on many sources. Some are facts, some hypotheses, some opinions. Most - including many of my own statements - are mixtures. Even ’facts’ are unavoidably selective and can rarely be guaranteed. Despite careful checking, neither I nor my colleagues or publishers can accept responsibility for any errors, misinformation or unsuitable advice. This also applies to opinions - particularly on issues affecting health and safety. As any recommendations must balance complex, often opposing, factors, not everyone will reach the same conclusions. In this -as indeed in every issue this book touches on -every reader must make up her or his mind, for which they alone must be responsible. I offer the best advice I am capable of, but every circumstance is different. Anyone who acts on this advice must make their own evaluation, and adapt it to their particular circumstances. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress ISBN: 978-0-7506-8449-1 ~ For information on all Newnes publications visit our website at www Elsevier corn Printed and bound in Great Britain 08091011 12 10987654321 Working together to grow libraries in developing countries I www.eIsevier.com I www.bookaid.org I www.sabre.org I 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 changesofuse ........................................... 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 circuitkystems ................................ 21 Periodic testing ......................................... 21 Voltage drop in conductors ................................ 23 Contents 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 Methodone ............................................ 40 Methodtwo ............................................ 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 Z, ................................ 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 Methodone ............................................ 82 Methodtwo ............................................ 83 Prospective fault current test ................................. 92 Functional testing ......................................... 98 Residual current device (RCD) .............................. 98 Typesof RCD ........................................... 98 RCDs and supply systems ................................ 101 Testing of RCDs ........................................ 103 Contents 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 Cablesand 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