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Electrics
G e o f f r ey B u r d e tt
Revised by
W. Turner
Heinemann Newnes
Heinemann Newnes
An imprint of Heinemann Professional Publishing Ltd
Halley Court, Jordan Hill, Oxford 0X2 8EJ
OXFORD LONDON MELBOURNE AUCKLAND SINGAPORE
IBADAN NAIROBI GABORONE KINGSTON
First published by Butterworth & Co (Publishers) Ltd 1977
Reprinted 1978, 1980, 1981, 1983 (with revisions)
Second edition first published by Heinemann Professional Publishing Ltd 1987
Reprinted 1987, 1990
© Heinemann Professional Publishing Ltd 1987
ISBN 0 434 90199 7
Printed and bound in Great Britain by
Butler & Tanner Ltd, Frome and London
Preface
A home will not look after itself, and
the occupant must be prepared to do battle
with damp, rust and corrosion, fading,
peeling, woodworm, leaks, blown fuses-
and much more besides.
Of course you can call in a man, but
with so much of the work labour-intensive—
the areas where costs are now so very
high-you will have to delve deep in your
pocket to keep up with the bills. From
this stems the great incentive to tackle the
work yourself; if you can reduce costs to
materials only, this will have two immediate
effects. First, you will have money to do
more and, secondly, you may have money
available with which to buy better quality
materials and add the frills.
The term do-it-yourself encompasses a
very wide field of activity, and there is
much to learn. It is not always easy, but
once new skills have been mastered d-i-y
becomes rewarding and satisfying. The
books in this series, which as well as home
electrics covers subjects ranging from
decorating and plumbing to heating, are
designed to help you acquire the necessary
skills. All you need to add is practice!
They are written by people with very
considerable practical experience in the
d-i-y field, and all have been involved in
feature-writing for DIY magazine over the
years. The authors have also been respon
sible for dealing with hundreds of readers
queries—which has given them an invaluable
insight into the problems encountered in
and about the house.
I'm sure you will find their advice in
valuable. May I wish you success in all you
undertake.
Tony Wilkins,
Consultant Editor, Do-it-Yourself Magazine
Acknowledgements
The author and publishers would like to
thank the following firms for their help in
supplying information and illustrations
relating to their products.
AMF-Venner Ltd.
Belling & Co Ltd.
BSR (Housewares) Ltd.
BICC Ltd.
E. Chidlow & Co Ltd.
Concord Lighting International Ltd.
J. A. Crabtree & Co Ltd.
Creda Electric Ltd.
Crownette Water Heaters Ltd.
Duraplug.
Egatube Ltd.
Electrical Association for Women.
Electricity Council.
Fotherby Willis Electronics Ltd.
Home Automation Ltd.
Humex Ltd.
Lewdon Metal Products Ltd.
Maclamp Co Ltd.
M.E.M. Ltd.
Μ Κ Electric Ltd.
Osram-GEC Ltd.
Ottermill Switchgear Ltd.
Philips Electrical Ltd.
Rock Electrical Accessories Ltd.
Santσn Ltd.
George H. Scholes & Co Ltd.
Superswitch Electrical Appliances Ltd.
Thermair Electrical Appliances Ltd.
Introduction
Home electrical work whether it is meriding
a fuse, fitting a plug, adding a light or socket
outlet or even completely rewiring a house
is within the capabilities of the keen mecha
nically minded d.i.y man (or woman).
Electricity, because it flows along wires
instead of through pipes, cannot be seen or
heard nor produces any smell, is often
regarded with great mystery. This is really a
fallacy since the actual wiring, fixing acces
sories and other associated work is very
much a practical and down to earth exercise
requiring no physics degree nor a college
diploma. Most of the work is non-electrical
and consists of lifting floorboards, drilling
holes and fixing cables and boxes.
Since an electrician is paid the same rate
for the job, whether he is lifting floorboards
or connecting up a consumer unit, you can
save a lot of money by doing the work
yourself, your only outlay being materials.
Prices charged by contractors vary con
siderably but you can take it that in
general the cost of materials represents only
a fraction of the total.
Safety is an important aspect. Before you
start any electrical work on the house, switch
off at the mains. If repairing an appliance,
pull out the plug. Follow the instructions
given in this book implicitly, using the
correct materials and the correct sizes and
types of cables and you are unlikely to go
wrong.
Chapter 1
fuse and a neutral link; the meter, and,
when required, a time switch for off-peak
Your loads. This apparatus is connected together
by cables and is sealed to prevent unauthor
ised persons tampering with the supply.
electrical
The householder is not concerned with
the board's apparatus unless the service fuse
installation blows and the board has to be called in to
replace it. The consumer can however be
held responsible for any damage to the
board's equipment.
All apparatus on the house side of the
The home electrical installation is in two meter is the responsibility of the consumer.
parts. One part belongs to the electricity This consists of one or more consumer
board. The other part which is termed 'the units or, in older houses which may not
consumer's installation' belongs to the house have been rewired, a number of main switch
owner. and fuse units and fuseboards. See page 4.
The components of the electricity board's
installation consist of the incoming cable
known as 'the service cable' which runs in
from the street (usually underground but Mains layout and equipment showing how the consumer
unit is connected to the mains via the electricity meter;
often overhead in rural areas), the service
the earthing connections are also shown
Circuits
o 0
Consumer unit
G OG
OFF
G G
Red cable Meter
Fuses
ON
Service fuse -
Earttiing lead* 6 or lOmm^ green-yellow
PVC insulated cable
Eorttiing clonnp
Underground service cable
* Provided by consumer. Sizes agreed with boord.
— — — — Lighting circuit
Sub circuit
^•"g circuit
Cor^sumer
unit
Meter
Mams
supply
Earthing^
As will be mentioned in later sections an
Circuit fuse
.installation and most of the appliances have
to be connected to earth. Earthing is the
responsibility of the consumer and not the |- Main switch
electricity board. and fuse unit
Nevertheless, the electricity board, where
possible, provides earthing facilities by
means of an earthing terminal situated near
the meter and connected by the board to
its system. This earthing is usually the metal
sheath or armour of the service cable.
Where the electricity board is unable to
provide earthing facilities the consumer
must do so. Almost invariably this will
necessitate fitting an earth leakage circuit
breaker to be used in conjunction with
some form of earth electrode, such as an
earth rod driven into the ground outside
the house.
Three separate main switch and fuse units connected to
the mains via a terminal distribution box, and used instead Main leads to mains
of a single consumer unit; are shown on the right
Two consumer units are shown below. One is for general
use, the other for off-peak loads connected to a dual-
rate meter
Normal
Off-peoK circuits circuits
Dual-rote meter
I 1
I 1 Fuses 1^ Fuses
Time Off-peak Unrestricted
switch consumer unit supply consumer unit
9 I ^1
Mains leads
Earthing^ to a water pipe
power supply to the faulty circuit. It can
Many installations are earthed to the mains be regarded as a main switch having an
water pipe but water authorities are now automatic switching off device. (See also
using plastic pipes which means the water Miniature Circuit Breakers).
pipe may no longer be satisfactory as. the There are two principal types of ELCB;
sole means of earthing. If in doubt, it is one current operated and one voltage
essential to check with the electricity board operated. The current-operated ELCB has
whether it is advisable to use the existing been renamed Yesidual-current device' and
water pipe earthing arrangement. In the the voltage-operated ELCB has been re
great majority of cases the board will
named 'fault-voltage operated protective
provide an earthing terminal and the instal
device'.
lation should be earthed to this: if not, an
Both types have been used in the past
ELCB may be required as indicated earlier.
but the Regulations do not now permit the
Crossbonding^ of services use of the voltage-operated type; the current
operated (residual current) type should
therefore be used for new work. It is not
In any case the mains water and the mains
essential to replace any existing voltage-
gas services must be crossbonded to earth.
operated types but if work is being done on
This is also the responsibility of the con
the installation it is desirable to replace
sumer when installing new wiring or
them by the current-operated type.
rewiring an existing installation.
To crossbond, an earthing clamp is
Residual-current device (RCD)
secured to the mains water pipe on the
house side of the house stop cock and to a
The residual-current circuit breaker operates
clamp secured to the main gas pipe on the
on the principle of detecting out-of-balance
house side of the gas meter. The two clamps
currents caused by earth leakage. Under
are connected to the installation earthing
normal conditions the current returning by
system by 6 or 10 mm^ green-yellow PVC
the neutral pole is equal to the current flow
insulated cable.
in the phase pole. When current leaks to
Earthing conductors earth, the amount returning through the
neutral is reduced, so upsetting the balance
The ECC (earth continuity conductor) of a
in the ELCB. As a result the trip coil is
circuit has been renamed CPC (circuit
energised and trips the circuit breaker.
protective conductor).
The previous green colour of the An RCD protecting the whole installation
insulation of all earth conductors and of is either fitted as a separate unit between
PVC sleeving enclosing bared ends of earth the consumer unit and the meter or in the
conductors (CPCs) has now been changed consumer unit in place of the conventional
to green-yellow striped. mainswitch.
For the protection of a single circuit
How an ELCB operates supplying socket outlets and providing
personal protection from electrocution, an
An ELCB is a form of switch (actually RCD operating at 10 or 30 mA is normally
a circuit breaker) having a tripping coil used, the 30 mA type being the more
which, when energised by an earth-fault common.
current flowing through the system, trips, Socket outlets which may be used to
opens the circuit breaker, and cuts off the supply portable appliances outdoors via
Circuit cables-
Circuit protection
conductor
Test V I "rest
<O0 Nb utton ^^UF 0>O Nb utton
--Current operated - -Voltage operated
OFF ELCB OFF ELCB
Earthing lead| Earthing lead I
I
/
To boards meter / To board's meter
Clamp"= / Clamiqf:
-Earth rod in soil * 1200 mm Earth rod in soil *
u
* Required only when eorthing terminal is not provided by board.
The connections at the mains for a current-operated earth
/ea/<age circuit breaicer (residual-current device) and a
voltage-operated earth leakage circuit breaker
flexible cables must be protected by a lation are the lighting and the power circuits.
residual-current device operating at not Lighting circuits are confined principally
more than 30 mA. See page 45. to supplying the lighting but are sometimes
used for supplying electric clock points,
Fault voltage operated protective device electric shaver sockets and fans.
In a two-storey house it is usual to have
Since this type of circuit breaker is not
two lighting circuits, one for each floor.
now permitted by the Regulations it is not
In a bungalow the two circuits are, or
described further in this book.
should be, fairly evenly divided between
the lighting points. In major rooms in a
Lig^hting^ circuits bungalow, the circuits could to advantage
overlap so that the lighting in such rooms
The principal circuits of the home instal is supplied from more than one circuit.
