Electrical Installations and Regulations

98 Pages·1974·10.442 MB·English

by  Michael Neidle (auth.)

ELECTRICAL INSTALLATIONS AND REGULATIONS
ELECTRICAL INSTALLATIONS
AND REGULATIONS
Michael Neidle
Associate Member of the Institute of Electrical Engineers
T.Eng.(C.E.I.), F.I.T.E., A.S.E.E. (Dipl.)
Southall College of Technology
© Michael Neidle 1974
All rights reserved. No part of this publication
may be reproduced or transmitted in any form
or by any means without permission
First published 1974 by
THE MACMILLAN PRESS LTD
London and Basingstoke
Associated companies in New York Dublin
Melbourne Johannesburg and Madras
SBN 333 15462 2
ISBN 978-1-349-02089-8 ISBN 978-1-349-02087-4 (eBook)
DOI 10.1007/978-1-349-02087-4
Typeset in Great Britain by
PREFACE LIMITED
Salisbury, Wilts
The paperback edition of this book is sold subject to the condition that it shall
not, by way of trade or otherwise, be lent, re-sold, hired out, or otherwise
circulated without the publisher's prior consent in any form of binding or
cover other than that in which it is published and without a similar condition
including this condition being imposed on the subsequent purchaser.
To Hetty, Stephen, Peter, Andrea and Daniel Marc
CONTENTS
Preface ix 4.3 Bending 27
4.4 Conduit care and earthing 27
1 INSTALLATION FUNDAMENTALS 4.5 Concealed and surface work 27
1.1 Basic functions 4.6 Prefabricated .conduit systems 28
1.2 Electricity Supply Regulations 1 4.7 Wiring operations 28
1.3 Electricity Factory Acts 2 4.8 Exercises 28
1.4 I.E.E. Wiring Regulations 2
1.5 Cable insulators 3 5 PVC-SHEATHED CABLES 29
1.6 Conductors 3 5.1 1· and 2-way switch control 29
1.7 Accessories 4 5.2 Intermediate and series-parallel switching 30
1.8 Soldering lugs to cables 5 5.3 Use of joint-boxes 30
1.9 Exercises 6 5.4 Voltage drop 31
5.5 Regulations 32
2 TRANSMISSION AND DISTRIBUTION 8 5.6 Installation layout 32
2.1 3-phase 4-wire distribution 8 5.7 Exercises 34
2.2 Intakes 9
2.3 Domestic intakes 10 6 MINERAL-INSULATED CABLES 35
2.4 Industrial intakes 11 6.1 Sealing 35
2.5 Diversity 12 6.2 High-temperature seals 36
2.6 The 30 A ring circuit· 13 6.3 Wiring methods 36
2.7 Radial circuits using fused plugs 14 6.,4 Fixings 37
2.8 Voltage drop 14 6.5 Corrosion hazards 37
2.9 Exercises 18 6.6 Voltage surges 37
6.7 Earth concentric wiring 38
3 STEEL CONDUIT SYSTEMS 20 6.8 Exercises 38
3.1 Types 20
3.2 Boxes and fittings 20 7 TRUNKING SYSTEMS 39
3.3 Bending 21 7.1 Cable trunking 39
3.4 Conduit care 22 7.2 Fittings 40
3.5 Concealed and surface work 23 7.3 Precautions 40
3.6 Wiring operations 1 23 7.4 Segregation 40
3.7 Wiring operations 2 24 7.5 Plastics trunking 41
3.8 Prefabricated conduit systems 25 7.6 Ducting 42
3.9 Exercises 25 7.7 Busbar trunking 43
7.8 Exercises 44
4 PVC CONDUITS 26
4.1 Types 26 8 PROTECTION 45
4.2 Boxes and fittings 26 8.1 Rewirable fuses 45
8.2 High breaking-capacity (HBC) fuses 46 10.3 Tungsten lamps 67
8.3 Circuit-breakers 48 10.4 Fluorescent lighting 69
8.4 Miniature circuit-breakers 48 10.5 Illuminance values 70
8.5 Close and coarse excess-current protection 49 10.6 Neon sign installations 71
8.6 Provision of protective devices 50 10.7 Light-source efficacy 72
8.7 Discrimination 51 10.8 Exercises 72
8.8 Earthing 51
8.9 Earth-leakage circuit-breakers 53 11 HEATING 74
8.10 Double insulation and shaver sockets 55 11. 1 Heat and temperature 74
8.11 Monitored earthing 55 11.2 Calculations 75
8.12 Safety on building sites 55 11.3 Heat transmission 75
8.13 Treatment for electric shock 56 11.4 Thermostats 76
8.14 Exercises 56 11.5 Space heating schemes 77
11.6 Water heating 79
11.7 Regulations 80
9 TESTING AND MACHINE INSTALLATION 58 11.8 Exercises 80
9.1 Testing 58
9.2 Verification of earthing 58 12 BELL AND ALARM SYSTEMS 82
9.3 Insulation resistance 60 12.1 Trembler bells 82
9.4 Certification 61 12.2 Indicator boards 83
9.5 Ring-circuit test 62 12.3 Signalling systems 84
9.6 Installation of machinery 62 12.4 Luminous call systems 85
9.7 Exercises 63 12.5 Fire alarms 85
12.6 Burglar alarms 86
12.7 Exercises 86
10 LIGHTING 65
Answers to Exercises 88
10.1 Basic considerations 65
10.2 Inverse square law 65 Index 89
PREFACE
Electrical Installations cover almost every aspect of our students in their present studies, it is also aimed to equip
national life-domestic, recreational, medical, commercial them for the changes that lie ahead in this developing field.
and industrial. The Wiring Industry is one which is progressive The wider application should also prove of interest and benefit
and continually expanding; present annual turnover is about to all personnel engaged in, or interested in the many aspects
£400 million. Electric wiring has a scientific basis in addition to of the expanding industry.
obvious utilitarian aspects. Installations may in fact be defined The text contains Model Answers which are aimed at
as one of the practical branches of electrical engineering which is instilling a systematic and logical approach to dealing with
concerned with the utilisation and safe application of installation problems. Changing the words into a picture often
electricity. In addition there is a creative aspect; it is therefore presents students with difficulties; it is hoped that these can be
not surprising that many of the eighty thousand personnel overcome by careful study of the numerous diagrams pre·
engaged in the industry find it of absorbing interest. sented here.
The gaining of the Electrical Installation Work, City and Basic principles and the practical side of electrical installa
Guilds No. 235, Course B Certificate gives the technical tion work are too often learned as unrelated topics. Here,
requirements necessary to become an Approved Electrician wherever possible, theory and practice are linked in order to
with an appropriate increase in the rate of pay. The Course 8 produce a real mastery of the subject. The modern approach is
Award can also be one of the decisive steps leading to aimed at encouraging safety consciousness, by providing the
technician, electrician, supervisor, contracts manager and student with a thorough knowledge of the applications of the
higher posts. In this book, the experience obtained through I.E.E. Wiring Regulations.
many years work on actual installations and in teaching has Grateful acknowledgement is given to the following com·
been specifically directed towards easing the difficulties of panies and authorities: BICC Ltd; City and Guilds of London
candidates. Institute; Drake and Scull Ltd; Egatube Ltd; Gilflex Conduits
While the primary purpose of the book is to assist course 8 Ltd; Hartley Electromotive Ltd; Key Terrain Ltd.
1 INSTALLATION FUNDAMENTALS
1.1 BASIC FUNCTIONS
W1ring is an essential requirement for conveying, safely and
efficiently, electrical energy from the point of supply to the
current-using devices such as lamps, heaters and motors. As a
result of the almost unlimited variations in buildings, con
ELECTRICITI' ~ UPPL ACf • I to 1936
ditions of service and rating of electrical apparatus there are
many different kinds of wiring system. But whatever the type,
installations must conform to the safety rule: All apparatus
and conductors shall be sufficient in size and power for the ELECTRICITY SUPPLY R GULATIO S,
work they are called upon to do, and so constructed, installed,
1937
protected, worked and maintained, as to prevent danger as far
as is reasonably practicable.
For Securing the Safety of the Public and
This fundamental regulation is stated in each of the major
sets of regulations governing electrical installations: for Insuring a Prop r and Sufficient
The Electricity Supply Regulations (1937). Department of Supply of El rical Energy
Trade and Industry.
Electricity (Factories Act) Special Regulations ( 1908 and
1944). Department of Employment.
Regulations for the Electrical Equipment of Buildings.
Institution of Electrical Engineers.
There are also a number of mandatory regulations for
specialist installation requirements such as mines, cinemas and
overhead I ines Figure 1. 1 Electricity Supply Regulations state certain
general basic safety requirements
1.2 ELECTRICITY SUPPLY REGULATIONS
EXAMPLE 1. 1. A total current of 60 A flows in a 240 V
These are statutory requirements and therefore compulsory. In
installation. What must be the minimum value of insulation
the rna in they are concerned with the generation, transmission
resistance in order to conform with the Electricity Supply
and distribution of the National Grid supply (figure 1.1 ). The
Regulations?
Regulations (No. 22-35) which deal with consumers' premises
are of vital importance. They stipulate that Electricity Boards
have the power to withhold supply if any installation does not Maximum permitted 1
conform to certain essential requirements. leakage current=--- part of the total current
10 000
( 1) The insulation resistance must be such that the leakage
60
current in any installation does not exceed one ten-thousandth
= - - = 0.006 A or 6 rnA
part of the maximum current. 10 000
1
2 Electrical Installations and Regulations
By Ohm's law 1.4 I.E.E. WIRING REGULATIONS
minimum insulation V
resistance= - =2-4-0 This is ohen referred to as the electrician's bible; the first
I 0.006 edition was issued in 1882. The title-page (figure 1.3) shows
= 40 ooo·n that it was first published by the Society of Telegraph
Engineers and Electricians and entitled, Rules and Regulations
= 40 kD. for the Prevention of Fire Risks arising from Electric Lighting.
(2) All single-pole switches must be inserted in the live Ml
conductor. Referring to figure 1.2, since the neutral and earth
conductors are at the same potential, the lamp would be alive
to earth -with the switch in the off position - if the switch
were connected to the neutral instead of the live side.
Switch-sockets must also be connected in this manner. RULES ~D REGULATIONS
l'OR THE PREV~T!O~ OP FffiE RISKS ARISL'iG FRO~
ELECTRIC LIO~G,
........... '117 u. c-il .. ~ wi.cla lht 'Bepon ol u. c
Le-------¥ .uu.appomc.d bJ u.e., OD ll&Jll, 1S8S, to CiOIImdcr the Rbjeet.
E•-.--.--.---- ~.--~
KEMBERS OF THE COIDUTTEE.
Prof..or W. 0. Adami, F.R.S., Profes.or D. E. Bqhes, P .R.S.,
N••---/ ~------~ . Yic:e-P~ ·~Ptviklll.
Sir Chariel T. Brisht. W. B. Preece, P .R.S.. Put
nght wrong
T. ~ Cramptoa. ~
Figure 1.2 All single-pole switches must be connected in the 1L E. Cro!DptoD. .A.Jexu.w Siemeu~.
live conductor (Regulation 27(i) Electricity Supply Regula· w. Croota, ~ .R..S. C. E. Spapoletti, J.iu-~
tions) 'Wart~~~ De II. Roe, D.C.L .. P.R.S. James N. Shoolbred.
~ G. C. FOiter. F.~ Aq:"~ctal Stroh.
Patt4~ Sir William TboiUOII, F .R.S,. PGIIt
Ei..rud Gra•es. Prwidal.
An important point to note is that installations complying J. E. H. Oonlon. LleaL.Colooel C. E. 'W' ebber,lLE.,
with the Regulations for the Equipment of Buildings (I.E.E. Dr. 1. BopkiotoD, F.R.S. Prnidt. . t.
Wiring Regulations) are accepted as complying with the
These rules and regulations are dnwu up not only Cor the
Electricity Supply Regulations.
pid.s.nee and inatruction of those who h~•e electric lighi.llg
apparatll! i.nst&lled on their premi!es, but for the rednctioll t.o a.
1.3 ELECTRICITY FACTORY ACTS minimum of those risk.s of fire whlch are inherent tO e'l'ery srstem
ol artificial illumination.
These also are compulsory and apply to all premises that come
The chief dangers of every new o.pplicalion of electricity ar.3e
under the jurisdiction of the Factory Acts. While many of the mainly from ignor~U~ce o.ud inerperience on the'part of those wto
consumer requirements of the Electricity Supply Regulations 1Upply IJld fit up the r&:~pi.site pl:ml.
are common to the Electricity Factory Acts, the latter place The difficulties that beset the electricnl engineer a:e c:h:i!~J
special emphasis on motor control and the design and location iJ:I~mal n:ld invisible, :lnd they can only ~ effecttU)iy ;u :ccd
of switchboards. Regulation 12 may be taken as typical: aga.in~ by "testing,'' or probing w .th elcctnc cur:e::t-3. T~.ey
Every electrical motor shall be controlled by an efficient depend chiefly on leakage, undue resistance in the cc::c-...c• r. ::-::.!
t.d joints, which lead to "'aste of eocrg-y aoJ tbe yrcxluc::-:. of
switch or switches for starting and stopping, so placed as to be
heat. Tbeae defect.& can only be detected by mcn,ur:::;, by r~·~ ... ::-s
easily worked by the person in charge of the motor.
of rpeeial appuat~, the C'UTTents tb:~t ::.n.: ci~l .:.:r c;rl: ;,r,i;- o~ ~or
In every place in which machines are being driven by any
electric motor, there shall be means at hand for either
switching off the motor or stopping the machines if necessary Figure 1.3 Title·page of 1st Edition of the I. E. E. Wiring
to prevent danger. Regulations