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Consumer unit
From Wikipedia, the free encyclopedia
A consumer unit is a box of fuses or breakers, usually arranged in a single row. This is unlike a distribution board which has multiple rows of fuses or breakers and usually serves two or more locations, which may be split phase, two phase, two phases taken from three phase), or three phases.
A consumer unit fitted with just fuses is often referred to as a "fuse box".
The box pictured top-right is a "Wylex standard" fitted with rewirable fuses. These boxes can also be fitted with cartridge fuses or miniature circuit breakers (MCBs). This type of consumer unit was very popular in Britain until 2001 when wiring regulations mandated residual current device (RCD) protection for sockets that could "reasonably be expected to" supply outdoor equipment (BS7671:2001, ISBN 0-86341-373-0). There were a number of similar designs from other manufacturers but the wylex ones are by far the most commonly encountered and the only ones for which fuseholders/breakers are still commonly available.
Modern consumer units (picture bottom right) usually use DIN-rail mount breakers. Unforuntately while the rail itself and the shape of the front opening are standardized the busbar arrangements are not. Therefore mixing of brands should generally be avoided and where unavoidable care should be taken to ensure that the breaker chosen is a good fit for the busbars. Generally a "split load" arrangement is used with some circuits protected by the RCD and others not.