Merseyrentacom
supply a range of Consumer Units for flats and houses. Please use our
contact page for enquiries and to obtain price lists.
Information
Miniature Circuit Breakers (MCBs)
An MCB is a modern replacement for a fuse, the purpose of which is to
protect the wiring of its circuit from excessive current due to an overload
or short-circuit. If the rated current is exceeded, the MCB will trip,
and merely needs to be switched back on again to re-connect. It is thus
more convenient than a fuse, and more obvious that it has tripped. Common
values are 6A for lighting circuits, 16A for single sockets and immersion
heaters, 32A for ring mains, 7kW electric showers and electric cookers,
and 40A for 8kW showers and larger electric cookers.
Residual
Current Devices (RCDs)
RCDs are primarily designed to protect against accidental electrocution,
by detecting current flowing to earth. Because under normal circumstances
there should be very little earth current, they can be made very sensitive:
30 milliamps is common.
This sensitivity also gives it the ability to detect other faults such
as partial live/earth breakdown, which generates heat and can cause
fires. However, it cannot protect against the less common live-neutral
shock, and it does not protect against overloads so must always be used
in conjunction with MCBs or fuses. A device called a Residual Current
Breaker with Over-current protection (an RCBO) performs the functions
of earth leakage and over current protection, and is basically an RCD
and an MCB combined. Some RCDs/RCBOs have extra features, such as detection
of live/neutral reversal or earth disconnection (for which they need
an earth sense wire). A disadvantage of some RCBOs is that you cannot
tell if they were tripped by over current, or an earth fault. This can
make fault finding harder.
