Electrical Installation Work

491 Pages·2011·6.46 MB·English

by  Brian Scaddan

Electrical Installation Work
To my wife
Electrical Installation Work
Seventh Edition
Brian Scaddan

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
The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK
30 Corporate Drive, Suite 400, Burlington, MA 01803, USA
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
Sixth edition 2008
Seventh edition 2011
Copyright © 2011 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 at http://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
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: 978-0-08-096981-7
For information on all Newnes publications
visit our website at www.elsevierdirect.com
Printed and bound in Italy
11 12 13 14 15 11 10 9 8 7 6 5 4 3 2 1
Contents

Preface .............................................................................................................................xi
Mapping to City and Guilds 2357 Certificate in Electrotechnical Technology ......................xiii
CHAPTER 1 Basic Information and Calculations ..........................................................1
Units ................................................................................................................................. 1
Multiples and Submultiples of Units .................................................................................. 3
Indices ...............................................................................................................................4
Self-Assessment Questions .................................................................................................6
Simple Algebra .................................................................................................................. 6
Formulae or Equations .......................................................................................................7
Manipulation or Transposition of Formulae......................................................................... 7
Self-Assessment Questions ...............................................................................................12
The Theorem of Pythagoras ............................................................................................. 12
Basic Trigonometry ..........................................................................................................13
S elf-Assessment Questions......................................................................................... 15
Areas and Volumes ..................................................................................................16
CHAPTER 2 Electricity ............................................................................................17
Molecules and Atoms ...................................................................................................... 17
Potential Difference ..........................................................................................................20
Electron Flow and Conventional Current Flow ...................................................................20
Conductors and Insulators ...............................................................................................20
Electrical Quantities .........................................................................................................21
Ohm’s Law .......................................................................................................................27
Electricity and the Human Body ...................................................................................... 29
Types and Sources of Supply ........................................................................................... 30

Voltage Bands .................................................................................................................30
Measuring Current and Voltage ........................................................................................30
Components of a Circuit .................................................................................................. 31
Self-Assessment Questions......................................................................................... 32
CHAPTER 3 Resistance, Current and Voltage, Power and Energy ..................................33
Resistance ......................................................................................................................33
Voltage Drop ...................................................................................................................36
Power: Symbol, P ; Unit, Watt (W) .................................................................................... 46
Electrical Energy: Symbol, W ; Unit, kWh ..........................................................................51
Self-Assessment Questions......................................................................................... 56
CHAPTER 4 Electromagnetism ................................................................................59
Magnetism ......................................................................................................................59
Electromagnetism ...........................................................................................................60
Application of Magnetic Effects ........................................................................................64
Drawing the Waveform of an Alternating Quantity ............................................................. 70
Addition of Waveforms ....................................................................................................70
Root-Mean-Square (r.m.s.) Value .....................................................................................71
Average Value .................................................................................................................73
Three-Phase a.c. Generator .............................................................................................73
Inductance: Symbol, L ; Unit, Henry (H) ........................................................................... 74
v
vi Contents
Induced e.m.f. Due to Change in Flux ............................................................................. 75
Self-Inductance ...............................................................................................................75
Mutual Inductance: Symbol, M ; Unit, Henry (H) ..............................................................76
Time Constant: Symbol, T ................................................................................................77
Graphical Derivation of Current Growth Curve ..................................................................78
Energy Stored in a Magnetic Field ...................................................................................80
Inductance in a.c. Circuits ...............................................................................................80
Resistance and Inductance in Series ( R–L Circuits) ......................................................... 82
Impedance: Symbol, Z ; Unit, Ohm ( Ω ) ............................................................................ 83
Resistance and Inductance in Parallel .............................................................................85
Power in a.c. Circuits ......................................................................................................86
Transformers ....................................................................................................................89
Self-Assessment Questions ...............................................................................................93
CHAPTER 5 Capacitors and Capacitance ..................................................................95
Capacitors .......................................................................................................................95
Capacitance: Symbol, C ; Unit, Farad (F) ..........................................................................96
Dimensions of Capacitors ................................................................................................96
Capacitors in Series .........................................................................................................97
Capacitors in Parallel .......................................................................................................98
Capacitors in d.c. Circuits ................................................................................................ 99
Capacitance in a.c. Circuits ........................................................................................... 100
Capacitive Reactance: Symbol, X ; Unit, Ohm ( Ω ) ......................................................... 101
c
Resistance and Capacitance in Series ...........................................................................102
Resistance and Capacitance in Parallel .........................................................................103
Working Voltage ............................................................................................................103
Applications of Capacitors .............................................................................................104
Self-Assessment Questions ............................................................................................104
CHAPTER 6 Resistance, Inductance and Capacitance in Installation Work ................... 105
PF Improvement ........................................................................................................... 111
Self-Assessment Questions ............................................................................................120

CHAPTER 7 Three-Phase Circuits ............................................................................121
Star and Delta Connections ...........................................................................................121
Current and Voltage Distribution ....................................................................................122
Measurement of Power in Three-Phase Systems .............................................................126
Self-Assessment Questions ............................................................................................128
CHAPTER 8 Motors and Generators ........................................................................129
Direct-Current Motors ....................................................................................................129
The a.c. Motors .............................................................................................................140
Starters ......................................................................................................................... 149
Installing a Motor ..........................................................................................................153
Fault Location and Repairs to a.c. Machines .................................................................. 157
Power Factor of a.c. Motors ...........................................................................................157
Motor Ratings ...............................................................................................................162
Self-Assessment Questions ............................................................................................166
CHAPTER 9 Cells and Batteries ....................................................................................167
General Background .....................................................................................................167
The Primary Cell ...........................................................................................................167
The Secondary Cell ....................................................................................................... 167
Cell and Battery Circuits ................................................................................................174
Self-Assessment Questions ............................................................................................177
Contents vii
CHAPTER 10 Illumination and ELV Lighting ..............................................................179
Light Sources ................................................................................................................179
Lamp Types ...................................................................................................................180
Calculation of Lighting Requirements ............................................................................. 190
Self-Assessment Questions ............................................................................................200
CHAPTER 11 Electricity, the Environment and the Community ....................................201
Environmental Effects of the Generation of Electricity .....................................................201
New Developments .......................................................................................................205
The Purpose and Function of the National Grid .............................................................207
Generation, Transmission and Distribution Systems .......................................................208
The Aesthetic Effects of the Siting of Generation and Transmission Plant ........................209
CHAPTER 12 Health and Safety ..............................................................................211
Safety Regulations ..........................................................................................................211
The Health and Safety at Work Act 1974 ....................................................................... 213
Electricity at Work Regulations 1989 ..............................................................................215
Personal Protective Equipment Regulations (PPE) 1992 ................................................ 217
Construction (Design and Management) Regulations .....................................................217
Control of Substances Hazardous to Health Regulations ................................................218
Chemicals (Hazardous Information and Packaging for Supply) Regulations (CHIP) 2009....218
Working at Height Regulations 2005 ...............................................................................220
Control of Asbestos Regulations 2002 .............................................................................220
The Building Regulations ..............................................................................................220
General Safety ............................................................................................................... 221
The Mechanics of Lifting and Handling .......................................................................... 223
Work, Load and Effort .....................................................................................................226
Access Equipment ........................................................................................................228
The Joining of Materials .................................................................................................233
Fire Safety .....................................................................................................................233
Electrical Safety .............................................................................................................235
First Aid ........................................................................................................................237
Electric Shock ................................................................................................................237

CHAPTER 13 The Electrical Contracting Industry ......................................................239
Sample Specification ......................................................................................................243
Cost of Materials and Systems ........................................................................................248
CHAPTER 14 Installation Materials and Tools ............................................................253
Cables ...........................................................................................................................253
Jointing and Terminations ............................................................................................. 257
Plastics .........................................................................................................................263
Cable Management Systems ......................................................................................... 264
Fixing and Tools .............................................................................................................276
Comparison of Systems .................................................................................................281
Self-Assessment Questions ............................................................................................283
CHAPTER 15 Installation Circuits and Systems ..........................................................285
Lighting Circuits ............................................................................................................ 285
Lighting Layouts ............................................................................................................286
Power Circuits ............................................................................................................... 288
Space Heating Systems ..................................................................................................291
Radiant or Direct Heating ..............................................................................................291
Thermostats ...................................................................................................................293
Installation Systems .......................................................................................................295
Industrial Installations ...................................................................................................296
viii Contents
Multi-Storey Commercial or Domestic Installations ..........................................................296
Off-Peak Supplies .........................................................................................................301
Alarm and Emergency Systems .....................................................................................303
Call Systems .................................................................................................................307
Emergency Lighting Systems ..........................................................................................307
Central Heating Systems ...............................................................................................309
Extra-Low-Voltage Lighting .............................................................................................310
Choice of System ..........................................................................................................313
Special Locations ...........................................................................................................313
CHAPTER 16 Earthing and Bonding .........................................................................329
Earth: What It Is, and Why and How We Connect To It ...................................................329
Earth Electrode Resistance ............................................................................................332
Earthing Systems .......................................................................................................... 334
Earth Fault Loop Impedence .........................................................................................338
Residual Current Devices ..............................................................................................341
Requirements for RCD Protection ...................................................................................343
Self-Assessment Questions ............................................................................................347
CHAPTER 17 Protection .........................................................................................349
Protection .....................................................................................................................349
Control ..........................................................................................................................368
CHAPTER 18 Circuit and Design .............................................................................373
Design Procedure .........................................................................................................373
Design Current ..............................................................................................................373
Nominal Setting of Protection ........................................................................................374
Correction Factors ......................................................................................................... 374
Current-Carrying Capacity .............................................................................................376
Choice of Cable Size ......................................................................................................378
Voltage Drop .................................................................................................................378
Shock Risk .....................................................................................................................379
Thermal Constraints ... ....................................................................................................380
Selection of cpc Using Table 54.7 ..................................................................................380
Installation Reference Methods ......................................................................................384
Installation Methods .......................................................................................................386
CHAPTER 19 Testing ..............................................................................................393
Measurement of Electrical Quantities ..............................................................................393
Measurement of Current ...............................................................................................395
Measurement of Voltage ................................................................................................398
Instruments in General .................................................................................................. 399
Selection of Test Instruments ..........................................................................................400
Approved Test Lamps and Indicators .............................................................................401
Accidental RCD Operation ............................................................................................. 401
Calibration, Zeroing and Care of Instruments .................................................................402
Initial Inspection .............................................................................................................403
Testing Continuity of Protective Conductors.....................................................................405
Testing Continuity of Ring Final Circuit Conductors ........................................................408
Testing Insulation Resistance ........................................................................................411
Special Tests .................................................................................................................413
Testing Polarity ..............................................................................................................414
Testing Earth Electrode Resistance ................................................................................415
Testing Earth Fault Loop Impedance ..............................................................................417
Contents ix
External Loop Impedance Z ..........................................................................................419
e
Prospective Fault Current ...............................................................................................421
Periodic Inspection .......................................................................................................422
Certification ...................................................................................................................424
Inspection and Testing ..................................................................................................425
Fault Finding .................................................................................................................429
CHAPTER 20 Basic Electronics Technology ..............................................................431
Electronics Components ................................................................................................431
Semi-Conductors ..........................................................................................................434
Rectification ..................................................................................................................435
Electronics Diagrams .....................................................................................................441
Electronics Assembly ....................................................................................................443
Self-Assessment Questions .............................................................................................444
Answers to Self-Assessment Questions ..........................................................................445
Appendix .......................................................................................................................451
Index ............................................................................................................................471