Please read the disclaimer
before attempting any electrical work. If
you are uncertain then contact
a qualified electrician.
How to install a consumer
unit
Do not attempt to
remove, replace or interfere with any consumer
unit unless you are you are qualified to
Part P regulation standards.. It is an offence
to interfere with any of the electric boards
seals on the electricity meter. All wiring
and connections to the consumer unit must
be checked and tested by a qualified electrician.
Link
to part p competent person
A modern consumer unit complying distributes
electricity via MCB’s(miniature circuit
breakers) throughout the home, This is the
centre where all the wiring/cable goes back
to.
Firstly you should be aware there are
3 methods/boards available, there are single
load (rcd), split
load(rcd) and RCBO
(Click the images
to view products above)
All of the above comply with the 17th edition,
but different benefits differ between the
boards.
The single load RCD
consumer unit- if in the unfortunate
case there is a fault on a circuit then
you may be without any power at all (e.g.
a fault on the sockets could leave you without
your lights, cooker, smoke alarms and shower)
upstairs sockets
downstairs sockets
downstairs lights
upstairs lights
cooker
smoke alarms
kitchen sockets
shower
As they are very sensitive, it is not practical
to fit one RCD to protect the whole house
The split load RCD
consumer unit-if in the unfortunate
case there is a fault on a circuit then
you may be without any power on 1 side of
the board e.g. if you had :
| Left
hand side of consumer unit |
Right hand side
of consumer unit |
| upstairs sockets |
downstairs sockets |
| downstairs lights |
upstairs lights |
| cooker |
smoke alarms |
| kitchen |
sockets shower |
if there was a fault on your upstairs
lights you may be without all of the highlighted
circuits in red
“This is the most common consumer
unit my customers ask for as the cost is
very reasonable compared to the RCBO, its
more practical than the single load and
if you separate the circuits like above
you are always left with some power on every
floor ” Jamie Vernon - Online Electrical
Services Ltd
RCBO consumer unit-if
in the unfortunate case there is a fault
on a circuit then you would only be without
power on the 1 faulty circuit e.g if there
was a fault on the upstairs lights then
everything else in the home would remain
on:
upstairs sockets
downstairs sockets
downstairs lights
upstairs lights
cooker
smoke alarms
kitchen sockets
shower
Single load
consumer unit- The power
on the consumer unit coming in is taken
through a double pole switch to a RCD and
then to a separate live buss bar. Each,
MCB, is clipped onto a DIN bar and the "teeth"
of the buss bar are inserted into the bottom
of the MCB's. The cables to the house circuits
are connected to the top of the MCB's.
Split load
consumer unit -The power
on the consumer unit coming in is taken
through a double pole switch to both RCD’s
and then to 2 separate live buss bars. Each,
MCB, is clipped onto a DIN bar and the "teeth"
of the buss bar are inserted into the bottom
of the MCB's. The cables to the house circuits
are connected to the top of the MCB's.
RCBO consumer
unit- The power on the consumer
unit coming in is taken through a double
pole switch and then to a live buss bars.
Each, RCBO, is clipped onto a DIN bar and
the "teeth" of the buss bar are
inserted into the bottom of the RCBO. The
cables to the house circuits are connected
to the top of the RCBO. RCBO’s also
have an earth and neutral attached which
must be connected to the correct terminals.
A: Neutral terminal block
for RCD righrt side of the unit
B:
Neutral terminal block for RCD left side
of the unit
C: Earth terminal block
(takes both sides of unit)
D:
Main double pole isolating switch.
E: Generally 80 Amp RCD
with 30mA (milliamp) sensitivity.
F:
Generally 63Amp RCD with 30mA (milliamp)
sensitivity.
G: Neutral link cable from
main switch to top of RCD
H:
Neutral link cable from 80A RCD to neutral
terminal (right hand side)
I: Neutral link cable from
63A to neutral terminal block (left hand
side)
The
RCD is not just
a on - off switch but a very important sensitive
safety device. They cut off the power when
there’s a fault in a fraction of a
second, It also detects any imbalance between
Live and Neutral conductors which is essential
for Class 2 double insulated equipment.
RCDs can
be bought in different current ratings and
various sensitivities to current leakage,
you will need to check which ratings are
appropriate for your home.
Old main switch consumer units don’t
detect a neutral to earth fault (which means
the neutral conductor has contact with the
earth conductor) when the new 17th Edition
RCD consumer units are installed you may
find some circuits will not HOLD/power up,
this is because some where in the home this
has happened and in some cases can be quite
a pain to locate.
The use of RCDs
is necessary to meet the needs of the regulations.
To protect any socket which may be reasonably
expected to supply equipment outside the
house or special locations ( lawn mowers,
outside lights, bathroom etc). also to protect
every cable in the house that is buried
in the wall (excluding cables mechanically
protected and at a depth of more than 50mm)
RCDs have a
test button which creates an earth leak
with a resistor, most recommended that they
are tested quartaly. There should be a sticker
on the consumer unit explaining this. RCDs
can be manually switched and can also take
the place of the isolator switch/main switch
if they break live and neutral (double pole).
MCBs now conforming to the international
equivalent of our old imperial ratings (Renard
current rating).. the following fuses should
be replaced:
| OLD
FUSE SIZE |
NEW
MCB SIZE |
| 5 amp |
6 amp |
| 15 amp |
16 amp |
| 20 amp |
20 amp |
| 30 amp |
32 amp |
| 45 amp |
40 amp |
Picture above shows the live (J)
and neutral (K) coming
into the main double pole switch from the
meter. These cables are called the main
tails, and in this instance, the
size of the tails depends on the main fuse
size, for a 60A main fuse 16mm sq is substantial,
for a 100A main fuse 25mm sq is substantial.
in this case 25mm sq tails have been used.
This will vary and you should always check
with a qualified electrician.
The picture above shows the earth
cable from the meter (L). This screws into
the earth terminal block.
Picture of a cable entering board.
The picture above shows how a circuit cable
is introduced to the unit protected by the
right hand RCD (80A).
In this case it is a 1.00.mm lighting cable.
The live (M) is fixed into
the top of the MCB (P),
while the neutral (N) goes
to the Right hand side neutral terminal
block. The earth (o) is
in the number 1 terminal (which has been
left unsheathed for clarity only always
place earth sleeve over the earth ).
The picture above shows how a circuit cable
is introduced to the unit protected by the
left hand RCD (63A).
In this case it is a 1.00.mm lighting cable.
The live (S) is fixed into
the top of the MCB (T),
while the neutral (R) goes
to the left hand side neutral terminal block.
The earth (Q) is in the
number 6 terminal (the earth has been left
unsheathed for clarity only always place
earth sleeve over the earth ).
Each circuit cable is fed into the consumer
unit and connected to the appropriate amp/MCB
rating, in this case 6Amp for the lighting
circuit.
The above picture shows the MCB clipped
on to the DIN rail/bar. The live terminal
of the RCD and MCB are then connected tightly
to the buzz bar.
Always remember to stick all
warning lables on the consumer unit
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IMPORTANT:
This installation, or part of it,
is protected by a device which automatically
switches off the supply if an earth
fault develops.
Test quarterly by
pressing the button marked "T"
or "TEST". The device
should switch off the supply and
should then be switched on to restore
the supply.
If the device does
not switch off the supply when the
button is pressed, seek expert advice.
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 |
This
label should only be added if there
are new and old colours inside the
consumer unit.
CAUTION
This installation
has wiring colours to two version
of BS 7671.
Great care should
be taken before undertaking extension,
alteration or repair that all conductors
are correctly indentified.
|
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Always identify each individual
circuit.
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