Consumer's Power Supply Control Unit † this is conveniently
abbreviated to consumer unit. As described on the previous page,
it contains a supply isolator switch, live, neutral and earth bars,
plus a range of individual circuit over-load safety protection
devices. By historical reference this unit is sometimes referred to
as a fuse box, but modern variants are far more sophisticated.
Over-load protection is provided by miniature circuit breakers
attached to the live or phase bar. Additional protection is provided
by a split load residual current device (RCD) dedicated specifically
to any circuits that could be used as a supply to equipment
outdoors, e.g. power sockets on a ground floor ring final circuit.
RCD † a type of electro-magnetic switch or solenoid which
disconnects the electricity supply when a surge of current or earth
fault occurs. See Part 11 of the Building Services Handbook for
more detail.
Note that with an overhead supply, the MAIN SWITCH is combined
with a 100 mA RCD protecting all circuits.
Note:
Circuits (1) to fixtures, i.e. lights, cooker, immersion heater and
smoke alarms.
Circuits (2) to socket outlets that could supply portable equipment
outdoors.
Electrical Supply---Consumer Unit