1. Simplified exploded view
Electrical Work
free
electron
atom
free electron
nucleus
free electrons flowing
in all directions
copper wire
(i.e. conductor)
positive
electrons
Simplified exploded view
of a copper atom
negative
free electrons flowing in the same direction (an electrical current)
bulb
Battery and
bulb circuit
power source
break the circuit and the
current will cease to flow
switch
fuse
battery
cable 0.5 ohm
resistance
Equivalent circuit diagram with meter installed
Basic electrical theory
From Plumbing (3rd edition), R.D. Treloar, page 273 Copyright Blackwell Publishing Ltd, all rights reserved:

2. Production of direct current
Electrical Work 4V 4V 4V
12V 4V 4V 4V
12V
Electrical circuits in series
12V
12V
12V
12V
direct
current
(electron flow in
one direction) R
Electrical circuits in parallel
ammeter
dilute
sulphuric acid
alternating
current
(electron flow
back and forth) R
copper
cathode
(positive)
zinc anode
(negative)
soft iron
core
brown
black
black
grey
grey
Production of direct current
(principle of a battery)
brown
phase
grey
magnet
earth
brown
black
earth
Electrical current
Single phase supply
(230, ~ 50 Hz)
Three phase supply
(400 V)
From Plumbing (3rd edition), R.D. Treloar, page 275 Copyright Blackwell Publishing Ltd, all rights reserved:

3. Single and three phase connections from generator to consumer
Electrical Work
400 kV
super grid (to other power stations)
power generating
station
132 kV
national grid
station
transformer
grid substation
grid
substation
33 kV
heavy industry
33 kV
sub- station
6–25 kV
33 kV
substation
substation
substation
(3 phases and 1 common)
either on poles,
above or below
ground
light industry
11 kV
local substation
local substation
new
old
400 kV
water heater
lighting circuit
cooker
brown
black
red
yellow
downstairs
ring circuit (RCD
protected)
grey
blue
neutral
conductor
blue
black
main double
pole switch
(400 V between
any 2 phases)
industrial or
commercial customer
400 V
400 V
230 V
230 V
230 V
230 V
230 V
circuit
protective
conductor
domestic customers
meter
Single and three phase connections
from generator to consumer
circuit
breakers
or fuses
RCD
main fuse to
equipotential
bonding
Consumer unit
(fuse box)
Domestic connection
showing a TN-C-S system
concentric cable
Electrical supply
From Plumbing (3rd edition), R.D. Treloar, page 277 Copyright Blackwell Publishing Ltd, all rights reserved:

4. Electrical Work Electrical safety Approved test lamp tripping latch
bi-metallic
strip
current flow
magnetic
trip coi
minimal amount of
probe exposed
MCB, cartridge and
re-wirable fuse holders
Fused
test
lead
Approved
test lamp
proving unit to check
operation of test equipment
Typical test meter and proving unit
Locked off electrical circuits
Electrical safety
From Plumbing (3rd edition), R.D. Treloar, page 279 Copyright Blackwell Publishing Ltd, all rights reserved:

5. Electrical Work Earth continuity Equipotential bonding conductors
consumer
unit
exposed
structural
steelwork
10 mm2 cable
meter
600 mm
max
gas
meter
main
earth bar
electrical
supply
water
supply
oil supply
Equipotential bonding conductors
Temporary bonding wire
metal bath
and basin taps
exposed metal pipework
Typical earth clip to BS 951
radiator
metallic
waste pipe
Supplementary cross bonding
Earth continuity
From Plumbing (3rd edition), R.D. Treloar, page 281 Copyright Blackwell Publishing Ltd, all rights reserved:

6. Electrical Work Domestic house wiring 1 Ring final circuit
2.5 mm2 twin and
earth PVC cable
13 amp
socket
outlet
junction
box E N P N
spur outlet P E
Ring final circuit
neutral
conductor
1.5 mm2 twin and
earth PVC cable
to next light
circuit protective
conductor
to simplify the
illustration the
earth has been
omitted from
the lighting circuit
note the
lighting circuit
does not return
to the consumer
unit N P E
circuit
breakers
or fuses
RCD
main double
pole switch
1st floor
landing
switch
ceiling
rose
bulb
as switch is
operated the
contacts are
made
2-way switching
downstairs
hall switch
Lighting circuit
From Plumbing (3rd edition), R.D. Treloar, page 283 Copyright Blackwell Publishing Ltd, all rights reserved:
Domestic house wiring 1

7. Termination of cable to a plug
Electrical Work
21 amp double pole
switch with neon
light indicator
neon light
cpc (earth)
21 amp heat
proof flex
2.5 mm2 twin and
earth PVC cable
neutral
phase
thermostat
circuit breaker
or fuse
consumer
unit
3 kW
heater
element
Typical radial circuit to
an immersion heater
dhw storage
cylinder
thermostat
earth (green and yellow
or just green)
heat proof flex
live via the fuse
(brown or red)
earth
cable clamp
heater element
terminals
fuse
neutral
(blue or black)
Note: the second
colour listed represents
the old flexible cable
colours
Immersion heater connection
cable
Termination of cable to a plug
Domestic house wiring 2
From Plumbing (3rd edition), R.D. Treloar, page 285 Copyright Blackwell Publishing Ltd, all rights reserved:

8. Electrical Work Installation practices Terminating cables at
cpc must be the last
conductor to be
disconnected should
the supply cable be
pulled from the
appliance
conduit
floor board
cable not
subject to
undue
stress
slotted joist
conductors
securely
terminated
Terminating cables at
fixed appliances
50 mm
min
ceiling board
steel
conduit
protection of
cables in walls
50 mm
min
hole in centre line
of joist to prevent
weakening
Support of cables under floors
Installation practices
From Plumbing (3rd edition), R.D. Treloar, page 287 Copyright Blackwell Publishing Ltd, all rights reserved:

9. Electrical Work Electrical components 1 Bi-metallic strip Differential
power N
temperature
adjusting
screw
supply L
contacts
contacts
bi-metallic
strip
Invar rod
brass
brass tube
immersion
heater
element etc.
(reduced in size)
terminals
Invar steel
Bi-metallic strip
temperature setting control
Differential
expansion
terminals
step down
transformer
contacts
switch L
capillary tube
sleeve or pocket
into appliance N
Filament ignition
hammer
filament
spring
crystals
Thermostats
earth
bellows
pilot
sensor filled with a volatile fluid
Liquid expansion
electrode
spark
lead
step up
transformer L
Piezoelectric
ignition
pilot
flame N
Spark
generator
Spark ignition
Ignition devices
Electric thermostats
From Plumbing (3rd edition), R.D. Treloar, page 289 Copyright Blackwell Publishing Ltd, all rights reserved:
Electrical components 1

10. Electrical Work Electrical components 2 Transformer Relay Solenoid
soft iron
core
secondary
windings
primary
windings
terminals
high voltage
current
a.c.~
input
output
Transformer
electro-magnetic
force back and forth
armature
coil of wire
(solenoid)
low voltage
current
contacts
iron armature
yoke
valve
iron core
a.c.
Relay
Solenoid
Should a low voltage pass through the coil
the armature is drawn into the relay
making the high voltage contacts
d.c. in
out
d.c.
insulating
material
single diode rectifier
Rectifier
a.c.
bridge
rectifier
capacitor fitted
to c.h. pump
capacitor fitted
to c.h. pump
metal foil
plates
Printed circuit board (PCB) Capacitor
Contains many electrical components, such as
a transformer, relay and capacitor
Capacitor
Electrical components 2
From Plumbing (3rd edition), R.D. Treloar, page 291 Copyright Blackwell Publishing Ltd, all rights reserved:

11. Electrical Work
From Plumbing (3rd edition), R.D. Treloar, page 292 Copyright Blackwell Publishing Ltd, all rights reserved:

12. Central heating wiring systems
Electrical Work
domestic
circulator
3-port
mid-position
motorised
valve
cylinder
thermostat
room
thermostat
boiler
programmer
junction
box
electrical supply
Central heating wiring systems
From Plumbing (3rd edition), R.D. Treloar, page 293 Copyright Blackwell Publishing Ltd, all rights reserved:

13. Electrical Work Testing for insulation resistance Multi-test meter
earth
terminal
phase or
neutral
terminal
Testing for
insulation resistance
known earth
(e.g. screw of
plug outlet)
known earth
(e.g. screw of
plug outlet)
insulation
resistance
tester
exposed
metal
Multi-test meter
Able to undertake a whole
range of electrical tests, from
insulation resistance to earth
loop impedance
digital
multi-meter
Testing for
earth continuity
Inspection and testing of electrical work
From Plumbing (3rd edition), R.D. Treloar, page 295 Copyright Blackwell Publishing Ltd, all rights reserved: