Wiring Systems and Fault Finding For Installation Electricians By the same author 17th Edition IEE Wiring Regulations: Design and Verification of Electrical Installations, ISBN 978-0-7506-8721-8 17th Edition IEE Wiring Regulations: Explained and Illustrated, ISBN 978-0-7506-8720-1 17th Edition IEE Wiring Regulations: Inspection, Testing and Certification, ISBN 978-0-7506-8719-5 Electric Wiring: Domestic, ISBN 978-0-7506-8735-5 PAT: Portable Appliance Testing, ISBN 978-0-7506-8736-2 Electrical Installation Work, ISBN 978-0-7506-8733-1 Wiring Systems and Fault Finding for Installation Electricians Fourth edition Brian Scaddan IEng, MIET 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 published 1991 Second edition 1998 Third edition 2003 Fourth edition 2008 Copyright © 2008, Brian Scaddan. Published by Elsevier Ltd. All rights reserved The right of Brian Scaddan 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 ((cid:2) 44) (0) 1865 843830; fax ((cid:2) 44) (0) 1865 853333; email: [email protected]. Alternatively you can submit your request online by visiting the Elsevier website athttp://elsevier.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 British Library Cataloguing in Publication Data Scaddan, Brian Wiring systems and fault finding for installation electricians. – 8th ed. 1. Electric wiring – Inspection 2. Electric wiring – Testing I. Title 621.3’1924 Library of Congress Control Number: 2008927643 ISBN: 978-0-7506-8734-8 For information on all Newnes publications visit our website atwww.elsevierdirect.com Typeset by Charon Tec Ltd., A Macmillan Company. (www.macmillansolutions.com) Printed and bound in Slovenia 08 09 10 11 11 10 9 8 7 6 5 4 3 2 1 Wiring Systems and Fault Finding for Installation Electricians v Contents PREFACE ............................................................................................. ix CHAPTER 1 Diagrams ..........................................................................1 BS EN 60617 Symbols ..........................................................................1 Diagrams .............................................................................................. 5 Circuit Convention .................................................................................9 Constructing and Interpreting Circuit Diagrams ....................................10 Heating and Ventilation System ...........................................................13 Relay Logic .........................................................................................15 Programmable Logic Controllers ..........................................................17 Drawing Exercises ...............................................................................22 C HAPTER 2 Wiring Systems ................................................................23 Radial Systems ................................................................................... 23 Ring Circuits .......................................................................................26 Distribution Systems ............................................................................26 Emergency Lighting Systems ............................................................... 32 Security and Fire Alarm Systems ......................................................... 36 Call Systems ....................................................................................... 40 Motor Starter Circuits .......................................................................... 42 Central Heating Systems .....................................................................46 Extra Low-Voltage Lighting ...................................................................49 Domestic Telephone Systems .............................................................. 51 CHAPTER 3 Testing and Test Instruments ...........................................53 Measurement of Electrical Quantities ...................................................53 Selection of Test Instruments ............................................................... 54 Approved Test Lamps and Voltage Indicators .......................................55 Accidental RCD Operation ...................................................................55 Calibration, Zeroing and Care of Instruments .......................................56 v vi PAT: Portable Appliance Testing Contents Continuity of Protective Conductors .....................................................57 Continuity of Ring Final Circuit Conductors ..........................................61 Insulation Resistance ..........................................................................66 Polarity ...............................................................................................69 Earth Fault Loop Impedance ...............................................................70 Earth Electrode Resistance ..................................................................74 Functional Testing ...............................................................................79 Prospective Fault Current .................................................................... 81 CHAPTER 4 Fault Finding ...................................................................85 Signs and Symptoms ........................................................................... 85 Ring and Radial Socket Outlet Circuits .................................................87 Radial Circuits Feeding Fixed Equipment .............................................88 Cable Fault Location ............................................................................89 Emergency Lighting .............................................................................91 Security and Fire Alarm Systems .........................................................92 Call Systems .......................................................................................92 Central Heating Systems .....................................................................93 Motor Starter Circuits ..........................................................................94 Conclusion and a Cautionary Tale ........................................................98 A PPENDIX 1 Shock Risk and Safe Isolation ......................................101 Electric Shock ................................................................................... 101 Safe Isolation of Supplies ................................................................... 107 A PPENDIX 2 Basic Electrical Theory ................................................109 Electrical Quantities and Units .......................................................... 109 Power, Current and Voltage ............................................................... 113 A PPENDIX 3 Solutions .....................................................................115 Quiz Controller (Chapter 1) ................................................................ 115 INDEX............................................................................................... 119 To my son, Stephen This page intentionally left blank Preface The aim of this book is to help the reader to approach the drawing and interpretation of electrical diagrams with confidence, to under- stand the principles of testing and to apply this knowledge to fault finding in electrical circuits. The abundant colour diagrams with associated comments and expla- nations lead from the basic symbols and simple circuit and wiring diagrams, through more complex circuitry, to specific types of wiring systems and, finally, to the methodical approach to fault finding. The new edition has been brought fully in line with the 17th Edition IEE Wiring Regulations. Brian Scaddan, April 2008 Acknowledgements I would like to thank Paul Clifford for his thorough technical proof-reading. ix