What is a Distribution Board?

A distribution board is a panel or enclosure that houses the fuses, circuit breakers, and ground leakage protection units used to distribute electrical power to numerous individual circuits or consumer points. The board typically has a single incoming power source and includes a main circuit breaker and a residual current or earth leakage protection device. Older distribution boards may include a series of fuses which supply the individual circuits; newer installations typically feature mini circuit breakers. A distribution board may be used to distribute either single or three phase supplies depending on the installation specifics. Although distribution board equipment, layouts, and legislative requirements differ from country to country, the basic principles of “distributing” a single supply to various individual points while ensuring safety and control for each remains the same.

Distribution boards are common place in most industrial installations and commercial or residential buildings. Most consist of a panel or enclosure supplied with a single incoming electrical feed cable. The power is then split among several small circuit breakers or, in the case of older boards, fuses which in turn feed power to different consumption points or circuits. The core function of any distribution board is to allow individual circuits to draw power from correctly rated circuit breakers and for those circuits to be isolated without causing a disruption to the rest of the supply. Most importantly though, the distribution board offers protection to users and equipment from electrical shock or fire resulting from ground faults.

Most distribution boards feature a single incoming supply cable feeding multi- or single-phase power to the board. The live feed from this cable is generally first connected to a main breaker, fuse, or residual current detector (RCD). These components allow the whole board to be isolated for repairs in the case of a main breaker or fuse while the RCD protects against ground fault shock and fire hazards. In the case of a single phase supply, the live feed is taken from the main breaker or RCD and bridged across the top of a series of individual fuses or mini circuit breakers. Multiphase supplies typically have several circuit breakers for each phase and with each group bridged along their incoming terminals. The neutral and earth cores of the supply cable are then connected to separate busway bars.

Cables from the individual power outlets, light circuits, or machine points are then inserted into the distribution board on the opposite side of the supply cable. The live leads from each cable are connected to suitably rated circuit breakers and the neutral and ground leads to the appropriate busway bars. This creates a distribution environment where each circuit is fed by a suitable circuit breaker and may be isolated if the need arises without disrupting the rest of the supply.

The most important part of any distribution board is, however, the RCD. This is the component which stands between the circuit user and potentially fatal electric shocks and catastrophic fires. For this reason, these units should be correctly rated, regularly tested, and never bypassed. The cause of a tripped breaker or blown fuse should also always be investigated prior to a reset to avoid possible damage to equipment or appliances and electrical shock.