Electrical installation work

435 Pages·2005·5.3 MB·English

by  Brian Scaddan IEng

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Electrical Installation Work
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To my wife
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Electrical Installation Work
Fifth Edition
BRIAN SCADDAN
AMSTERDAM •BOSTON •HEIDELBERG •LONDON
NEW YORK •OXFORD •PARIS •SAN DIEGO
SAN FRANCISCO •SINGAPORE •SYDNEY •TOKYO
Newnes is an imprint of Elsevier
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Newnes
An imprint of Elsevier
Linacre House,Jordan Hill,Oxford OX2 8DP
30 Corporate Drive,Burlington,MA 01803
First published 1992
Reprinted 1993
Second edition 1996
Reprinted 1996,1997
Third edition 1998
Reprinted 1999 (twice),2000,2001
Fourth edition 2002
Reprinted 2003,2004
Fifth edition 2005
Copyright ©1992,1996,1998,2002,2005,Brian Scaddan. 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.
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British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloguing in Publication Data
A catalogue record for this book is available from the Library of Congress
ISBN 0 7506 6619 6
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Contents
Preface xi
Mapping to City and Guilds 2330 Certificate in xii
Electrotechnical Technology
1 Basic information and calculations 1
Units 1
Indices 4
Simple algebra 6
Formulae or equations 7
Manipulation or transposition of formulae 8
The theorem of Pythagoras 12
Basic trigonometry 13
Areas and volumes 15
2 Electricity 16
Molecules and atoms 16
Potential difference 19
Electron flow and conventional current flow 19
Conductors and insulators 19
Electrical quantities 19
Ohm’s law 27
Electricity and the human body 28
Types and sources of supply 29
Voltage bands 29
Measuring current and voltage 30
Components of a circuit 31
Self-assessment questions 31
3 Resistance,current and voltage,power and energy 33
Resistance 33
Voltage drop 35
Power 45
Electrical energy 51
Tariffs 52
Measuring power and energy 52
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vi Contents
Water heating 53
Efficiency 54
Self-assessment questions 55
4 Electromagnetism 58
Magnetism 58
Electromagnetism 59
Application of magnetic effects 63
Drawing the waveform of an alternating quantity 68
Addition of waveforms 69
Root-mean-square (r.m.s.) value 70
Average value 71
Three-phase a.c. generator 71
Inductance 72
Induced e.m.f. due to change in flux 73
Self-inductance 74
Mutual inductance 74
Time constant 76
Graphical derivation of current growth curve 76
Energy stored in a magnetic field 78
Inductance in a.c. circuits 78
Resistance and inductance in series (R–Lcircuits) 81
Impedance 81
Resistance and inductance in parallel 83
Power in a.c. circuits 84
Transformers 87
Self-assessment questions 92
5 Capacitors and capacitance 94
Capacitors 94
Capacitance 95
Dimensions of capacitors 95
Capacitors in series 96
Capacitors in parallel 97
Capacitors in d.c. circuits 98
Capacitance in a.c. circuits 99
Capacitive reactance 99
Resistance and capacitance in series 100
Resistance and capacitance in parallel 101
Working voltage 101
Applications of capacitors 101
Self-assessment questions 101
6 Resistance,inductance and capacitance in installation work 103
Power factor improvement 108
Self-assessment questions 117
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Contents vii
7 Three-phase circuits 118
Star and delta connections 118
The neutral conductor 118
Current and voltage distribution 119
Measurement of power in three-phase systems 123
Self-assessment questions 124
8 Motors and generators 126
Direct-current motors 126
Alternating-current motors 136
Starters 145
Installing a motor 149
Fault location and repairs to a.c. machines 152
Power factor of a.c. motors 156
Motor ratings 158
Self-assessment questions 161
9 Cells and batteries 162
General background 162
The primary cell 162
The secondary cell 163
Cell and battery circuits 168
Self-assessment questions 171
10 Illumination and ELV lighting 172
Light sources 172
Calculation of lighting requirements 182
Self-assessment questions 192
11 Electricity,the environment and the community 194
Environmental effects of the generation of electricity 194
New developments 198
The purpose and function of the National Grid 198
Generation,transmission and distribution systems 199
The aesthetic effects of the siting of generation and 200
transmission plant
12 Health and safety 202
The Health and Safety at Work Act 1974 203
Electricity at Work Regulations 1989 205
Personal Protective Equipment Regulations (PPE) 207
Construction (Design and Management) Regulations (CDM) 207
Control of Substances Hazardous to Health Regulations (COSHH) 207
The Building Regulations 208
General safety 208
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viii Contents
The mechanics of lifting and handling 210
Work,load and effort 213
Access equipment 215
The joining of materials 219
Fire safety 220
Electrical safety 221
First aid 223
13 The electrical contracting industry 225
Sample specification 229
Cost of materials and systems 234
14 Installation materials and tools 239
Cables 239
Jointing and terminations 243
Plastics 248
Conduit 249
Trunking 255
Traywork 260
Fixing and tools 260
Comparison of systems 265
Self-assessment questions 266
15 Installation circuits and systems 268
Lighting circuits 268
Lighting layouts 270
Power circuits 271
Space heating systems 274
Thermostats 276
Installation systems 278
Industrial installations 278
Multi-storey commercial or domestic installations 282
Off-peak supplies 284
Alarm and emergency systems 286
Call systems 290
Emergency lighting systems 291
Central heating systems 292
Extra-low-voltage lighting 294
Choice of system 295
16 Earthing and bonding 304
Earth:what it is,and why and how we connect to it 304
Earth electrode resistance 307
Earthing systems 309
Earth fault loop impedence 312
Residual current devices 315
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Contents ix
Supplementary bonding 316
Points to note 318
Self-assessment questions 319
17 Protection 320
Protection 320
Control 335
Points to note (IEE Reglations) 339
18 Circuit and design 341
Design procedure 341
Design current 341
Nominal setting of protection 342
Correction factors 342
Current-carrying capacity 345
Choice of cable size 346
Voltage drop 346
Shock risk 347
Thermal constraints 347
Example of circuit design 351
Design problem 357
19 Testing 358
Measurement of electrical quantities 358
Measurement of current 360
Measurement of voltage 362
Instruments in general 363
Selection of test instruments 365
Approved test lamps and indicators 366
Accidental RCD operation 367
Calibration,zeroing and care of instruments 367
Initial inspection 368
Testing continuity of protective conductors 370
Testing continuity of ring final circuit conductors 372
Testing insulation resistance 375
Special tests 377
Testing polarity 378
Testing earth fault loop impedance 379
External loop impedance Z 381
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Prospective fault current 381
Testing earth electrode resistance 382
Functional testing 384
Periodic inspection 386
Certification 388
Inspection and testing 390
Fault finding 394