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Guide
to your fuse box (consumer unit)
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A consumer unit or fuse box is a particular
type of distribution board comprising a co-ordinated assembly
for the control and distribution of electrical energy,
principally in domestic premises. A consumer unit incorporates
a manual means of isolation on the incoming circuit(s)
- a main switch, and an assembly of one or more fuses,
circuit-breakers or residual current devices. |
A = Main switch
B = Circuit breakers
C = Residual current device
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| Circuit breakers, fuses and RCDs are protective devices
that will interrupt the flow of electrical current if the
circuit concerned develops a fault.
Instead of a modern unit like the one shown above with
circuit breakers and RCDs, some older houses have fuse
boxes with rewireable fuses. |
Fuses
Rewireable fuses have a piece of special fuse wire
running between two screws. The fuse wire generates
heat when a fault current flows through it and it
melts when the heat exceeds the acceptable level.
The melted fuse breaks the circuit and stops the
electricity supply. |
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Circuit Breakers
A circuit-breaker is an
automatic switch fitted to each circuit in the
consumer unit which switches off in the event of a
short circuit, an overload or a fault to earth on
the circuit. It is not usually required to operate
very often.
A circuit-breaker is much the same size as a fuse
holder, but give more precise protection than
cartridge fuses. When they 'blow' or 'trip', they
are simply reset instead of needing replacement or
rewiring.
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RCDs
A residual current device is a mechanical
switching device or association of devices intended
to cause the opening of the contacts when the
residual current attains a given value under
specific conditions, such as under earth fault
conditions. |
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Main Switch
The main switch allows you to turn off the
electricity supply to the electrical installation.
Note that some electrical installations may have
more than one main switch. For example, if your
house is heated by electric storage heaters, you
will probably have a separate main switch and
consumer unit arranged to supply them. |
It is important to know where the consumer unit is located
and that it is accessible. It is also important that you
know where the main switch(es) are in order to turn it
(them) off in the event of an emergency.
If your electrical installation includes one or more residual
current devices (RCDs), it is important that they are
checked regularly. You can do this by following the instruction
label, which should be located near the RCD. The label
will read as follows:
Who is Responsible
official stuff.
Fun Stuff
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