Modern Wiring Practice This page intentionally left blank Modern Wiring Practice Design and Installation Revised edition W E Steward and T A Stubbs With technical contributions by Trevor Marks and Steve Clarke AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Newnes is an imprint of Elsevier Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 200 Wheeler Road, Burlington, MA 01803 First published 1952 Twelfth edition published 1995 Reprinted 1996, 1997, 1998, 2000, 2002 (twice), 2003 Revised and updated 2005 Copyright © 1952, 1995 W E Steward and T A Stubbs All rights reserved Copyright © 1995 Trevor Marks Additional material Twelfth edition All rights reserved The right of W E Steward and T A Stubbs to be identified as the authors of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publisher Permissions may be sought directly from Elsevier’s Science and Technology Rights Department in Oxford, UK: phone: (ϩ44) (0) 1865 843830; fax: (ϩ44) (0) 1865 853333; e-mail: permissions@elsevier.co.uk You may also complete your request on-line via the Elsevier homepage (http://www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’ British Library Cataloguing in Publication Data Steward, W E Modern Wiring Practice – 12Rev.ed I Title II Stubbs, T A 621.31924 Library of Congress Cataloguing in Publication Data Steward, W E (William E.) Modern wiring practice: design and installation/W E Steward and T A Stubbs; with technical contributions by Trevor Marks and Steve Clarke.— 13th ed p cm includes index ISBN 7506 6662 (pbk.) Electric wiring, Interior I Stubbs, T A II Title TK3271.S8 1994 621.319’24—dc20 ISBN 7506 6662 For information on all Newnes publications visit our website at www.newnespress.com Typeset by Charon Tec Pvt Ltd, Chennai, India www.charontec.com Printed and bound in Great Britain by MPG Books Ltd, Bodmin, Cornwall 94-24608 CIP Contents Preface Acknowledgements Part DESIGN OF ELECTRICAL INSTALLATION SYSTEMS ix x Regulations governing electrical installations Planning of installation work The Electricity Safety, Quality and Continuity Regulations 2002 IEE Wiring Regulations – BS 7671 The Electricity at Work Regulations 1989 British Standards The Low Voltage Electrical Equipment (Safety) Regulations 1989 Health and Safety at Work Act 1974 (reprinted 1977) 3 12 16 Designing an electrical installation Assessment of general characteristics Electromagnetic compatibility Maintainability Systems of supply Protection for safety Protection against electric shock Protection against thermal effects Protection against overcurrent Protection against undervoltage Isolation and switching Circuit design Summary Design by computer 18 18 22 22 23 27 27 31 32 37 38 39 66 82 Tables from IEE Regulations for Electrical Installations 93 16 17 vi Contents Distribution of supplies in buildings Main switchgear Main switchgear for domestic installations Main switchgear for industrial installations Distribution boards Colour identification of cables and conductors Distribution circuits Protective multiple earthing (PME) Power factor 103 106 112 115 123 129 132 133 134 Design and arrangement of final circuits Final circuit feeding fixed equipment or A sockets Final circuit feeding 13 A sockets to BS 1363 Final circuit for socket outlets to BS 196 Final circuit for socket outlets to BS EN 60309 Final circuits feeding fluorescent and other types of discharge lighting Final circuits feeding motors Final circuits feeding cookers 137 138 141 147 148 Special types of installation Bath and shower rooms Swimming pools, paddling pools and hot air saunas Off-peak heating Underfloor and ramp heating Installations in hazardous areas Electrical installations for caravan parks and caravans Installations on construction sites Emergency supplies to premises Fire alarms Highway power supplies 161 161 163 163 164 166 167 169 171 177 177 Part PRACTICAL WORK 149 151 159 179 A survey of installation methods 181 Conduit systems The screwed steel conduit system Installation of screwed conduit Protection of conduits Termination of conduit at switch positions Termination of conduit at other than switch positions 203 203 207 225 225 226 Contents Removal of burrs from ends of conduit Conduit installed in damp conditions Continuity of the conduit system Flexible conduit Surface conduits feeding luminaires and clocks Drawing cables into conduits Looping in Some practical hints Conduit screwing machines Conduit cutting Checking conduit for obstructions Bending conduit Drilling and cutting The concealed screwed conduit system The light gauge unscrewed conduit system Insulated conduit system vii 227 227 228 228 229 230 233 233 234 234 234 235 236 237 242 244 Trunking systems Metallic trunking Non-metallic trunking Cable ducts Underfloor trunking systems 251 251 256 260 261 10 Busbar and grid catenary systems Busbar system Grid catenary system 267 267 270 11 Power cable systems Armoured, insulated and sheathed cables Cable tray, cable basket and cable ladder 273 273 275 12 All-insulated wiring systems Surface wiring Concealed wiring 284 285 288 13 Installation of mineral insulated cables 293 14 Luminaires, switches, socket outlets and accessories Ceiling roses Luminaires Flexible cords Lampholders Socket outlets and plugs Switches 306 306 307 308 309 310 312 viii Contents 15 Earthing 316 16 Inspection and testing Inspection Testing Continuity tests Insulation resistance Polarity Earth electrode resistance Earth fault loop impedance Testing residual current circuit breakers Completion Certificates and Inspection Report Forms Notice of re-inspection and testing 323 323 324 325 326 328 329 330 331 Index 331 332 335 Preface This book surveys the broad spectrum of electrical design and installation work, and this edition has been revised to incorporate the latest amendments to BS 7671 (The IEE Wiring Regulations) issued in 2004 The book is intended to supplement the various regulations and items of legislation It is not a replacement for them The book is divided into two sections: (1) design of electrical installation systems and (2) practical work The design section attempts to explain in simple terms the various regulations and requirements and goes on to deal with such matters as main switchgear, distribution, final circuits and special types of installations The practical sections, dealing with the most important wiring systems, is based on the author’s experience, and includes many on-site illustrations and diagrams The author hopes that readers will gain much useful information from the book Any comments on the new edition will be most welcome T.A Stubbs Inspection and testing 333 Fig 16.10 A digital residual current device tester Devices with ratings from to 500 mA may be tested (Edgcumbe Instruments Ltd) 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 published by the Institution of Electrical Engineers Date of last inspection Recommended date of next inspection Fig 16.11 tion notice Wording specified by the IEE Regulations for the periodic inspec- testing, and completing the inspection certificate needs to take account of these issues In the absence of other local or national regulations, a maximum period of five years would be applied, with shorter periods where appropriate This page intentionally left blank Index Access, 15–16, 23 Accessories, 306–15 Agricultural premises, 176–7 Agricultural (Stationary Machinery) Regulations 1959, Air circuit breaker, 121 Alarms, fire, 176, 177, 251 All-insulated wiring systems, 284–92 concealed wiring, 288–92 surface wiring, 285–7 Alterations to installations, 8–9 Aluminium conductors, 134, 196 Ambient temperature, 49–50, 189–90 correction factor, 50 low-temperature areas, 192–4 Animals, 176–7 Armoured cables, 273–5, 320 current ratings, 274 for PME supplies, 134 grouping, 274 Assessment of general characteristics, 10, 18–19 Atmosphere, explosive, 167, 190 Automatic disconnection, 29, 63–5 Avoidance of pipework, 223–5, 290 Bare conductors, 132 Barrier, fire, 191–2 Basket, cable, 275 Bathrooms, 161–3, 308, 310, 318 earthing, 321, 322 Bending: cable tray, 276 conduit, 235–6, 249 mineral insulated cables, 294, 295 Bends: conduit, 213, 216, 219 PVC cables, 287–8 trunking, 252–3 Boards, distribution, See Distribution boards Boiler houses: cables, 189–90, 191 installation design, example, 69–82 Bonding: equipotential, 9, 29, 63, 318, 321 MI cables, 296 Box: inspection, 213–14 tap-off, 267, 269 Breakers, See Circuit breakers Breaking capacity, 35 British Standards, 5, 16 BS 7671, 5, 6–12, 16 Building sites, 169–71 Building Standards (Scotland) Regulations 1990, Bunching of cables, 9, 194–5 Burrs, removal of from conduit, 227 Bus section switches, 118, 119 Busbar: chambers, 120, 123 expansion joints, 268–9 isolation, 269 overhead system, 267, 268 rising mains, 269–70 system, 267–9 trunking, 259, 268–9 336 Index Cab-tyre system (CTS), 284 Cable, 273–83 aluminium, 196 armoured, 134, 273–5, 320 basket, 275 bunching of, 194–5 catenary system, 270–2 colours, 129–33, 308 connections, 198 connectors, 200 corrosive liquid exposure, 190 crimping, 200–203 current-carrying capacities, 95, 97 discharge, 283 distribution circuits, 133 drawing into conduit, 230–3, 249–50 ducts, 191, 260 emergency supplies, 175–6, 251 explosive atmosphere exposure, 190 factors, 101 flexible, See Flexible cords four core, 43–4 glossary, 183 grouping, 48–54 heat resisting, 188–9, 191 identification, 129–33, 183, 192 in conduits, 205 in trunking, 101, 252–3, 254–5 insulated, 273–5 insulation testing, 326–8 joints, 198–9 ladder, 275 lift shafts, 159 location, 187 looping in, 233 low-temperature areas, 192–4 LSF, 188, 274–5 mineral insulation (MI), 132, 186–8 multicore, 42–4, 134, 291–2, 320 operating temperatures, 190 paper-insulated, 282–3 parallel connection, 42–4 PILC, 273, 274, 282 PVC covered, 188, 252–3, 273, 284–92 PVC/SWA/PVC, 183, 185, 188, 273–4 reduced neutral, 43–4 reels, 230 resistance, 102 runs, 186–90 segregation, 197–202, 251 selection of, 186–90 service, 103–4 sheathed, 273–5, 284–92 single-core, 194, 195 size of, 45–6, 48 spiking, 283 spurs, 144–6 stripping, 291, 298–301 switch, 130–2 thermal insulation effect, 50–1 trays, 275–82 XLPE, 188, 273, 274 See also Conductors; Wiring Cable management systems, 181 Capacitors, power factor improvement, 136 Caravan parks, 167–8 Caravans, 167 installations, 168–9, 287 Catenary system, 270–2 PVC sheathed cable suspension, 291 Ceiling: conduit, 241 roses, 306–7 Certificate of Completion, 331–2 Chamber, busbar, 120, 123 Characteristics: general, assessment of, 10, 18–19 of supply, 20 Charts, circuit, 129 Circuit: Band I, 197 Band II, 197 charts, 129 cooker, 159 design, 39–40, 44–5 computer-aided, 82–92 Index worked example, 69–82 discharge lighting, 149–51 distribution, 133 final, See Final circuit labelling, 129 monitoring, 173 motor, 58, 132–3 number of circuits, 40–2 polyphase, 150 resistance, 65–6 ring, 58, 325 socket-outlet, 52 subdivision, 40–2 See also Current Circuit breakers, 10, 34–5, 106–7, 108 air, 121 domestic installations, 112–15 in neutral conductors, 120–1 miniature, 37, 113, 124–6 moulded case (MCCB), 112, 115 residual current, 29–31, 113–15 testing, 331 See also Fuses Circuit protective conductor (cpc), 9, 316–18 Clamps, 200 Class equipment, protection by, 28–9 Clips: all-insulated wiring, 291–2 conduit, 216, 222–3 girder, 222–3 Clocks, conduits, 229 Coal and Other Mines (Electricity) Order 1956, 12 Colour identification, 129–33 flexible cords, 308 Commercial installations: final circuits, 146–7 switchgear, 116–19 trunking, 251–66 Compatibility: electromagnetic (EMC), 22 of equipment, 20–2 Competence, 16 Completion Certificate, 331–2 337 Computer design, 82–92 Concealed screwed conduit system, 237 Concealed wiring, 288–92 Concrete ducts, 260 Conductors: aluminium, 196 bare, 132 circuit protective (cpc), 9, 316–18 colour identification, 129–33 current-carrying capacities, 95, 97 earthed neutral, 120–2 earthing, 9, 316 equipotential bonding, 318, 321 supplemental conductor, 318 identification, 129–33 lightly loaded, 54–6 neutral, earthed, 120–2 PEN, 9, 132 protective, 9, 79, 316–20 size determination, 318–20 See also Protection resistance, 65–6, 102 size of, 45–6 thermal insulation effect, 50–1 See also Cable Conduit, 133, 203 bending, 235–6, 249 bends, 213, 216, 219 burrs, removal of, 227 cables in, 205, 230–3 ceiling points, 241 clips, 216, 222–3 concealed screwed system, 237 continuity of, 228 cutting, 234, 236–7 damp conditions, 227–8 dimensions, 204 drawing cables into, 230–3, 249–50 factors, 100–1 fittings, 213–16 fixing methods, 216–23 flexible, 228–9 identification, 192 338 Index Conduit (contd.) inspection, 213–14 installation, 207–8 insulated, 244–50 light gauge unscrewed, 242–4 looping in, 233 non-metallic, 244–50 obstructions, 234–5 plastic, 244–50 protection, 225 PVC, 244–6 runs, choice of, 208 saddles, 215–22 screwed copper, 207 screwed steel, 203–5 screwing machines, 234 siting, 223–5 size selection, 205–7 solid floors, 237–40 sunk, 242 supports, spacing of, 206 surface, 229 termination of, 225–6 at other than switch positions, 226 at switch positions, 225 wall outlets, 240–1 wooden floors, 237, 238 Connections, 14, 198 Connectors, 200–1 Construction sites, 169–71 Contact: direct, 10 indirect, 10 protection against, 63–5, 80–2 Continuity: of conduit system, 228 tests, 325–6 Control circuits, motor, 152 Cookers, 19 control units, 160 final circuits, 159–60 Copper conduit, 207 Cords, flexible, 308–9 definition, 309 extension, 308 for fused plugs, 146 for lighting, 140–1 Correction factors: ambient temperature, 50 derating, 47–51 grouping, 48–9, 53–6, 99 multiple, 51–3 Corrosive liquids, 190 Crimping, 200–202 Current: ambient temperature and, 49–50, 189–90 current-carrying capacities, 95, 97 demand assumptions, 139 designed circuit current, 44–5 excess production, 14 maximum demand, 19–20, 109, 136 nominal current of protective device, 45 overcurrent protection, 32, 106–8 short circuit, 59–60, 76–9 wattless, 135–6 Current ratings: armoured cables, 274 MI cables, 304 Cutting, conduit, 234, 236–7 Damp conditions, conduits, 227–8 Deburring conduits, 227 Defence regulation, 16 Definitions, IEE Regulations, 9–10 Department of Trade and Industry, Derating factor, 47–51 multiple factors, 51–3 Design, 18 by computer, 82–92 of circuit, 39–40 record sheet, 68 worked example, 69–82 Device: protective, See Protection residual current, 10, 29–31, 113–15 Direct contact, 10 Disabled people, sockets for, 312 Index Discharge lighting, See Electric discharge lighting Discharging cables, 283 Disconnection, automatic, 29, 63–5 Distance saddles, 219–21 Distribution, of supplies, 103–36 Distribution boards, 123–9, 138, 148 feeding, 128–9 marking, 129 positioning, 125 sunk conduits, 242 types of, 123–5 warning of maximum voltage, 127–8 Distribution circuits, 133 Diversity, 19–20, 44 allowances for, 110–11 calculation, 109 Domestic installation: intake position, 103 lighting, 139–40 standard sockets, 141–7 switchgear, 112–15 Drawing in cables, 230–3, 249–50 Drills, 236 Ducts: cable, 191, 260 concrete, 260 Earth electrode resistance test, 329 Earth fault loop impedance, 320 Earth fault protection, 61–3 Earthed equipotential bonding and automatic disconnection (eebad), 29, 64–5 Earthed neutral conductors, 120–2 Earthing, 14, 20, 316–22 conductor, 9, 316 functional, protective multiple earthing (PME), 25, 26, 133–4 Edison screw lampholders, 310 Elderly people, sockets for, 312 Electric discharge lighting, final circuits, 149–51, 152 circuit switches, 150 high-voltage circuits, 151 339 low voltage circuits, 149–51 polyphase circuits, 150 Electric fences, 177 Electric shock, 27 protection against, 27–8, 127–8, 161 severity, 63–4 Electrical installation, See Installation Electrical Installation Industry Liaison Committee, 145 Electrical testing guide, 17, 324–5 Electricity at Work Regulations 1989, 4, 12–16, 23 Electricity (Factories Act) Special Regulations 1944, 12 Electricity Regulations 1908, 12 Electricity Safety, Quality and Continuity Regulations 2002, 4, 5–6 Electricity supplier, 20, 103, 108 Electromagnetic compatibility (EMC), 22 Emergency lighting, 171–3, 198 systems, 173–4 Emergency supplies, 171–7 agricultural and horticultural premises, 176–7 standby supplies, 174–5 wiring system, 175–6, 251 Emergency switching, 39 motor circuits, 157 End preparation, MI cables, 297–8 Energy ‘let-through’, 35 Environment, 19 hazardous, 13 Equipment: Class 2, protection by, 28–9 compatibility, 20–2 erection, 11 outdoor, 142 selection, 11 Equipotential bonding, 9, 29, 63, 318, 321 supplemental conductor, 318 Erection of equipment, 11 340 Index Escape routes, emergency lighting, 171–3 Example circuit design, 69–82 Excess current production, 14 Expansion joints, 268–9 Explosive atmospheres, 167, 190 See also Flammable materials Exposed conductive part, 10 Extension: flexible cords, 308 trunking, 252 Extra-low voltage, 184, 197 Extraneous conductive part, 10 Factors: ambient temperature correction, 50 cable, 101 conduit, 100–1 derating, 47–51 fusing, 153 grouping, 48–9, 53–6, 99 multiple, 51–3 power, 135 improving, 136 Farm installations, 176–7 Final circuit, 137–60 cookers, 159–60 definition, 137 distribution board connection methods, 138 electric discharge lighting, 149–51, 152 feeding 13 A sockets, 141–7 for non-domestic premises, 146–7 fixed equipment or A sockets, 138–41 for socket outlets to BS 196, 147–8 for socket outlets to BS EN 60309, 148–9 motors, 151–9 regulations, 137–8, 140 See also Circuit Final testing, See Testing Fire: alarms, 176, 177, 251 barriers, 191–2 risks, 19 Fittings, conduit, 213–16 Fixing: conduit, 216–23 MI cables, 293–5 Flammable materials, 32, 166–7 explosive atmospheres, 167, 190 Flexible conduit, 228–9 Flexible cords, 308–9 colours, 308 definition, 309 extension, 308 for fused plugs, 146 for lighting, 140–1 Floors: all-insulated wiring, 290–1 conduit, 237–40 ducts, 260 traps, 237 trunking systems, 261–6 wooden, 237, 238 Fluorescent lighting, 155 circuit switches, 150 final circuits, 149–51 trunking, 255 Four core cables, 43–4 Functional: earthing, switching, 39 testing, 324–5 Fundamental safety requirements, Fuselinks, 147 for 13 A plugs, 146 Fuses: domestic installations, 112 flexible cords and, 140–1 high breaking capacity (HBC), 36–7, 107–8, 148, 153 in neutral conductors, 120–2 motor circuits, 152, 153 rating, 106 rewirable, 35–6, 107 semi-enclosed, 35–6, 53–4, 94 single-pole fusing, 124 Fusing factor, 153 Index Gas pipes, 223–5, 320 General characteristics, assessment, 10, 18–19 Girder clips, 222–3 Glass houses, 177 Glossary of cable terms, 183 Good workmanship, 184 Grid catenary system, 270–2 Grouping factor, 48–9, 99 relaxation, 53–6 Guard rails, 28, 119 Guide, electrical testing, 17, 324–5 Hand rail, 28, 119 Hazardous areas, 166–7 HBC fuses, See High breaking capacity (HBC) fuses Health and Safety at Work Act 1974, 4, 17 Health and Safety Commission, Heat, protection against, 31–2 Heating: off-peak, 163–4 ramp, 166 underfloor, 164–6 High breaking capacity (HBC) fuses, 36–7, 107–8, 148, 153 Highway power supplies, 17 Homes, old people, 312 Horticultural premises, 176–7 Hot air saunas, 163 Identification: cables, 129–33, 183, 192 MI cables, 305 conduits, 192 IEE Wiring Regulations BS 7671, 5, 6–12, 16, 18 tables, 93–102 Impedance, earth fault loop, 320 Indirect contact, 10 protection against, 63–5, 80–2 Induction motors, power factor, 135 Inductive loads, MI cables, 305 Industrial factory units, 44–5 341 Industrial installation: final circuits, 141, 146–7, 148–9, 156 stop buttons, 157, 158 switchgear, 115–22 trunking, 251–66 Inspection, 12, 323–4 box, 213–14 re-inspection notice, 332–3 Report Form, 331–2 Installation: agricultural, 176–7 alterations, 8–9 caravans and caravan parks, 167–9, 287 construction sites, 169–71 foundations of good installation work, 184 hazardous areas, 166–7 horticultural premises, 176–7 methods, 181–202 planning, 3–5 plastic conduit, 246–50 plastic trunking, 258–60 screwed conduit, 207–8 socket outlets, 310–12 special types or locations, 11, 161–77 See also Design; Domestic installation; Industrial installation Insulated: cables, 273–5 mineral-insulated (MI), 293–305 paper-insulated, 282–3 conduit system, 244–50 installation, 246–50 lampholders, 309 wiring systems, 284–92 Insulation, 13–14 MI cables, testing, 305 protection by, 28 tests, 326–8 thermal, 50–1 Intake position, 103, 104 Integrity, 14 342 Index Intended use of buildings, 19 Isolation, 14, 38–9 busbars, 269 motors, 152–3 Joints: all-insulated wiring, 284 between cables, 198–202 soldered, 198–200 Kitchens, 51, 308 installation design, example, 69–82 Label, warning, 127–8, 130 Labelling, 129 Ladder, cable, 275 Lampholders, 309–10 overcurrent protection, 138 Lamps: pilot, 160 protection against thermal effects, 32 See also Lighting; Luminaires Laundries, 322 ‘Let-through’ energy, 35 Liaison Committee, electrical industry, 145 Lifts, 158–9 Light gauge unscrewed conduit system, 242–4 Lighting: at work, 17 bath and shower rooms, 161 construction sites, 169–70 domestic, 139–40 electric discharge, final circuits, 149–51, 152 emergency, 171–4, 182 flexible cords, 140–1 industrial, 141 lift cages, 159 trunking system, 255–6, 262, 271 See also Lamps; Luminaires Lightly loaded conductors, 54–6 Live conductor, size of, 45 Live part, Live working, 15 Livestock, 176–7 Location: non-conducting, protection by, 31 special locations, 11 three-dimensional views, 87–9 Loop impedance, earth fault, 320 Looping in, 233 Low voltage, 184 circuits, 149–51 extra-low voltage, 184, 197 wiring, 184 Low Voltage Equipment (Safety) Regulations 1989, 4, 16–17 Low-temperature areas, 192–4 LSF cables, 188, 274–5 Lumen calculation, 85, 87 Luminaires, 307 conduits, 229 flexible cords, 140 petrol pump equipment, 166 protection against thermal effects, 32 See also Lamps; Lighting Mains, rising, 269–70 Maintainability, 22–3 Maintenance, preventative, 13 Marking, distribution boards, 129 Maximum current demand, 19–20, 109, 136 Metering, 103 Milking parlours, 177 Mineral insulated (MI) cables, 132, 186–8, 293–305 bending, 294, 295 bonding, 296 current ratings, 304 fixing, 293–5 identification, 305 inductive loads, 305 insulation test, 305 measurement, 305 protection against mechanical damage, 296 sealing, 301–3 cable end preparation, 297–8 Index regulations, 296–7 sheath stripping, 298–301 Mines, 16 Miniature circuit breakers, 37, 113, 124–6 Miscellaneous Mines (Electricity) Order 1956, 12 Monitoring circuit, 173 Motor vehicle ramp heating, 166 Motors: circuits, 58, 132–3 final circuits, 151–9 emergency switching, 157 isolators, 152–3 lifts, 158–9 protective device rating, 154 slip ring, 154–7 starters, 153–4 three-phase motors, reversing, 157–8 Moulded case circuit breaker (MCCB), 112, 115 Multibeam system, 281–2 Multicore cables, 291–2, 320 for PME supplies, 134 in parallel, 42–4 Multiple correction factors, 51–3 Multiple saddles, 221–2 Neon signs, 151 Neutral conductors, earthed, 120–2 Non-conduction locations, protection by, 31 Non-metallic: conduits, 244–50 trunking, 256–60, 264–6 Non-statutory regulations, See also Regulations Notice: of re-inspection and testing, 332–3 warning, 127–8, 130 Obstacles, protection by, 28 Obstructions, conduit, 234–5 Off-peak heating, 163–4 Old people, sockets for, 312 343 Open-type switchboard, 119 Operating temperatures, 190 Outdoor equipment, 142 Outlets, socket, See Sockets Overcurrent, 10 protection against, 32, 106–8, 138, 154 Overhead busbar system, 267, 268 Overheating, 11 Overload protection, 32–3, 46–8 ‘Package’ substation, 116, 122 Paddling pools, 163 Paint spraying, 166 Paper-insulated cables, 282–3 Parallel connection of cables, 42–4 PELV (protective extra-low voltage), 10, 28 PEN conductor, 9, 132 Petrol filling stations, 17, 26, 134, 167 Petrol pumps, 166–7 PILC cables, 273, 274, 282 Pilot lights, 160 Pin racks, 252 Pipework, avoidance of, 223–5, 290 Planning, installation work, 3–5 Plastic conduits, 244–50 installation, 246–50 Plastic trunking, 256–60 underfloor, 264–6 Plugs, 141–2, 310–12 flexible cords, 146 for socket outlets to BS 196, 147 fuselinks for 13 A plugs, 146 See also Sockets PME system, See Protective multiple earthing (PME) Polarity tests, 328–9 Polyphase circuits, 150 Pools, 163 Power factor, 135 improving, 136 Power posts, 186 Preventative maintenance, 13 Protected-type switchboard, 119–20 344 Index Protection: by earthed equipotential bonding and automatic disconnection (eebad), 29, 63–5 by insulation, 28 by isolation and switching, 38–9 by non-conducting locations, 31 by obstacles or placing out of reach, 28 by SELV, 28 by use of Class equipment, 28–9 conduits, 225 earth fault, 61–3 electric shock, 27–8, 127–8, 161 for safety, 11, 27 indirect contact, 63–5, 80–2 MI cables, 296 nominal current of protective device, 45 overload, 32–3, 46–8, 106–8, 138, 154 short circuit, 34–5, 59–63, 107, 154 thermal effects, 31–2 undervoltage, 37–8 Protective conductor, 9, 316–20 size determination, 318–20 Protective device: characteristics, 86 domestic installations, 112–15 industrial installations, 115–22 motor circuits, 154 See also Circuit breakers; Distribution boards; Fuses Protective multiple earthing (PME), 25, 26, 133–4 cables, 134 prohibition in petrol filling stations, 167 Pumps, petrol, 166–7 Purpose and use of buildings, 19 PVC conduits, 244–6 PVC covered cables, 188, 273, 284–92 bends, 287–8 concealed wiring, 288–92 in trunking, 252–3 stripping, 291 surface wiring, 285–8 suspension from catenary wires, 291 wiring to socket outlets, 291 PVC/SWA/PVC cables, 185–8, 273–4 Quarries, 16 Quarries (Electricity) Order 1956, 12 Ramp heating, 166 Record sheet, 68 Reduced neutral cable, 43–4 Reels, cable, 230 Regulation, defence, 16 Regulations: Agricultural (Stationary Machinery) 1959, Building Standards (Scotland) 1990, Electricity at Work 1989, 4, 12–16, 23 Electricity Safety, Quality and Continuity 2002, 4, 5–6 Electromagnetic Compatibility (EMC), 22 final circuit, 137–8, 140 Health and Safety at Work Act 1974, 4, 17 IEE Wiring Regulations BS 7671, 5, 6–12, 16, 18 Low Voltage Equipment (Safety) 1989, 4, 16–17 non-statutory, sealing of MI cables, 296–7 statutory, trunking systems, 253–5, 256–7 Reinspection notice, 332–3 Relaxation, of grouping factors, 53–6 Removal of burrs, conduit, 227 Requirements for Electrical Installations, IEE Wiring Regulations BS 7671, 5, 6–12, 16, 18 Residual current circuit breaker, 10, 29–31, 113–15 Index testing, 331 Resistance, 65–6 cable, 102 earth electrode, testing, 329 insulation, testing, 326–8 Reversing motors, 157–8 Rewirable fuses, 35–6, 107 Ring circuits, 58 continuity tests, 325 Rising mains, 269–70 Roses, ceiling, 306–7 Rotor circuits, 154–7 Runs: cable, 186–90 conduit, 208, 240–1 Saddles, 215–22 all-insulated wiring, 291–2 distance, 219–21 multiple, 221–2 spacer bar, 216–19 Safety: fundamental requirements, Health and Safety at Work Act 1974, 4, 17 protection, 11, 27 Saunas, 163 Screwed copper conduit system, 207 Screwed steel conduit system, 203–5 types of, 204–5 See also Conduit Screwing machine, conduit, 234 Sealing, MI cables, 301–3 cable end preparation, 297–8 regulations, 296–7 stripping the sheath, 298–301 Secretary of State, Secretary of state for Scotland, Segregation of cables, 197–202, 251 Selection of: cables, 186–90 conduit, 205–7 equipment, 11 switchgear, 108–11 345 SELV (separated extra-low voltage), 10 protection by, 28 Semi-enclosed fuses, 35–6, 53–4, 94 Service cables, 103–4 Shaver unit, 162 Sheathed cables, 273–5, 284–92 stripping, 291, 298–301 See also Mineral insulated (MI) cables; PVC covered cables Short circuit: current, 59–60, 76–9 protection, 34–5, 59–63, 154 Shower rooms, 161–3, 321 Single-core cables, 194, 195 Single-pole fusing, 124 Size of: cable, 45–6, 48 conduit, 205–7 protective conductor, 318–20 Skirting trunking, 253, 254 Slip ring motors, 154–7 Sockets, 310–12 A, 138–41 13 A, 141–7, 310 in trunking, 253, 254, 262–3 installation, 310–12 outlet circuits, 52 PVC cable wiring to, 291 to BS 196, 147–8 to BS EN 60309, 148–9, 310 Soldered joints, 198–9 Solid floors, conduit, 237–40 Spacer bar saddles, 216–19 Special installations or locations, 11 Spiking, cable, 283 Spurs: fused, 144–6 non-fused, 144 Standby supplies, 174–5 Starters, motors, 153–4 Statutory regulations, See also Regulations Steel: conduit system, 203–5 floor trunking, 261–3 Stop buttons, 157, 158 346 Index Storage heaters, 163–4 Strength and capability of installation, 13 Stripping: MI cables, 298–301 PVC sheathed cables, 291 Stroboscopic effect, 150–1 Subdivision of circuits, 40–2 Submains, 133 Substations, 104, 116 packages, 116, 122 Sunk conduit, 242 wiring, 242 Supplier of electricity, 20, 103, 108 Supply systems, 23–6, 104–5 characteristics, 20 distribution of, 103–36 emergency, 171–7, 251 highway, 177 intake position, 103, 104 standby, 174–5 Surface wiring, 285–7 Survey of installation methods, 181–202 Suspended PVC cables, 291 Swimming pools, 163 Switchboard, 105, 117–20 open-type, 119 protected-type, 119–20 Switches, 38–9, 312–15 bath and shower rooms, 161–2, 163 bus-section, 118, 119 control, 38 cookers, 160 emergency, 39, 157 fluorescent lighting, 150 functional, 39 motor circuits, 15 wires, 130–2 Switchgear, 105, 106–22 domestic installations, 112–15 industrial installations, 115–22 selection of, 108–11 Switching, See Switches System: of supply, 23–6 Tap-off units, 267, 269 Temperature: ambient, 49–50, 189–90 low-temperature areas, 192–4 resistance and, 65–6 thermal effects, protection against, 31–2 Testing, 12, 324–5 continuity tests, 325–6 earth electrode resistance, 329 earth fault loop impedance, 330 electrical testing guide, 17, 324–5 insulation resistance, 326–8 MI cable insulation, 305 notice of, 332–3 polarity, 328–9 residual current circuit breakers, 331 Thermal effects, protection against, 31–2 Thermal insulation, 50–1 Three-phase motors, 157 reversing, 157–8 Tools, 184 Tough rubber sheath (TRS), 284 Transformer, 116–18 Traps, 237 Trays, cable, 275–82 Trunking, 251–66 bends, 252–3 busbar system, 259, 267–9 cables in, 101, 252–3, 254–5 extensions, 252 lighting, 255–6, 262, 271 metallic, 251–6 mini, 261 non-metallic, 256–60 installation, 258–60 regulations, 253–5, 256–7 skirting, 253, 254 underfloor, 261–6 plastic, 264–6 steel, 261–3 vertical, 251, 252 Underfloor: heating, 164–6 Index trunking systems, 261–6 plastic, 264–6 steel, 261–3 Undervoltage, protection against, 37–8 Use of buildings, 19 Vertical: rising mains, 269–70 trunking, 251, 252 Voltage: drop, 56–8, 75–6, 96, 98 exceeding 230V a.c., 127–8 extra-low, 184, 197 See also Low voltage Wall outlets, conduit runs, 240–1 Warming, underfloor, 164–6 Warning label: supplies exceeding 230V a.c., 128 wiring colours, 130 Water heating, off-peak, 163 Water pipes, 223–5, 320 Wattless current, 135–6 347 Wiring: colour identification, 129–33 concealed, 288–92 emergency supplies, 175–6, 251 IEE Regulations BS 7671, 5, 6–12, 16, 18 tables, 93–102 low voltage, 184 sunk conduits, 242 surface, 285–7 switch wires, 130–2 systems, 181–2 all-insulated, 284–92 choice of, 182–3 See also Cable Wooden floors, conduit, 237, 238 Worked example, 69–82 Working: dead, 15 live, 15 Workmanship, 184 XLPE cables, 188, 273, 274 ... characteristics: (1 ) (2 ) (3 ) (4 ) Maximum demand Arrangements of live conductors and type of earthing Nature of supply Installation circuit arrangements Regulations governing electrical installations... divided into four parts which cover (1 ) system design and construction, (2 ) system maintenance to ensure safety, (3 ) all work activities on or near the system and (4 ) provision of protective equipment... two sections: (1 ) design of electrical installation systems and (2 ) practical work The design section attempts to explain in simple terms the various regulations and requirements and goes on to