Guide to installations Distribution Boards
Distribution board (DB)
Within a building, the electrical supply is distributed from the distribution board (DB). The main supply cable comes into the DB and is then distributed to the breakers and, from there, to all the circuits such as the geyser, lights and plugs.
The DB usually houses all the contact breakers, earth leakage unit and may also house items such as a doorbell transformer and timers. In a house, the main distribution board is usually where the main electrical cable enters, however there may be smaller boards with contact breakers and possibly earth leakage units at other points, including swimming pool pumps, gate motors and outbuildings. Various types of distribution boards are available, such as surface-mounted, flush-mounted or floor-standing; with closing doors or clear plastic covers or doors. These are available in diﬀerent sizes, which are determined by the number of circuits rewired within the board, referred to by some manufacturers as ‘modules’ and others as ‘ways’, for example 6-way,9-way, 12-way, 19-way, 24-way, 36-way, etc, or module.
The interior of the distribution board is pre-fitted with a clip tray or DIN rail for mounting the miniature circuit breakers (MCBs) and other devices. The two diﬀerent types of MCBs, referred to as ‘mini rail’ or ‘DIN’, are only interchangeable if special adaptor brackets are used. While mini rail MCBs can be slightly narrower than DIN MCBs (thus giving an advantage of fitting more into the same space available), the number of accessories on the market for this type of distribution board is limited as many manufacturers are now using the DIN format for their equipment. With the DIN format, the normal ranges of earth leakage units, disconnecting switches as well as MCBs are available.
In addition to this, various types of meters, time switches, pilot lights, surge arresters, etc, are manufactured and this now makes the DIN type distribution board very versatile. Distribution boards can be purchased as an empty enclosure to enable the contractor to equip it, as a ready-wired standard unit, or as a specially manufactured item to a client’s requirements. Also available are distribution boards for specific applications such as swimming pools, ready boards for low-cost housing, irrigation systems, etc. Each distribution board must be controlled by a switch disconnector (mains or main switch).