A Complete Guide to Distribution Boards

A distribution board or distribution panel (DP) is an important part of an electricity supply system. Its job is to split an incoming electrical power feed into multiple secondary or subsidiary circuits.

Most of the time, each of these secondary circuits will be protected with a fuse or breaker. In the UK, distribution boards like this are often referred to as consumer units in domestic properties.

The terms consumer unit and distribution board are not completely interchangeable. However, for most practical uses, they tend to mean the same thing. Distribution boards might also be called panelboards, breaker panels, or simply electrical panels.

A distribution board or breaker panel separates incoming mains power into various sub-circuits. Usually, all the fuses, breakers and other circuit protection devices for these secondary circuits will be held within the same single enclosure. However, not all distribution boards are necessarily enclosed; some are only semi-enclosed, while others are kept open.

Most workplaces rely on an electricity distribution board to divide and route a single source of outside power to multiple smaller circuits around the building. In many of these settings, the boards will be enclosed for safety. This enclosure is often referred to as a fuse box.

Whether it is an outdoor distribution board, a commercial distribution board, or a dedicated lighting distribution board for large public venues, all these variants essentially do the same thing. They take an incoming electrical connection, split it several ways, and reroute it to multiple sub-circuits.

This enables more precise and granular control of the supply to different areas, including the ability to isolate and shut down parts of the circuit without completely killing incoming power.

It also provides additional safety features - typically fuses, breakers, and RCDs - that allow for safer use of mains power. As each branch circuit has an individual safety cut-off, the entire electrical system is better protected against overloads, short circuits, and other hazards.

Consumer unit distribution panels come in various common types.

• Main switch consumer units are considered among the safest and most robust protective devices for incoming mains power. All circuits are fully separated, and each is independently protected from earth leakage via RCBOs (residual current breaker with overcurrent protection)
• Dual RCD consumer units are a step down in terms of protective capacity but are still suitable for most standard uses. They consist of two circuit banks, each protected by one of a pair of RCD (residual current device) breakers. These offer robust protection against overheating and electrical fires, or accidentally touching a live wire
• High integrity consumer units are more common in larger buildings where high numbers of sub-circuits are branching off from the incoming mains supply. They combine dual RCD protection with additional RCBOs that can be added in a wide range of flexible configurations

In addition to consumer units, there are various other types of electrical panel boards and sub-distribution boards in widespread use.

Type A distribution boards and Type B distribution boards offer different configurations of busbars, and varying compatibility with certain overcurrent protective devices (OCPD). When selecting a DP for installation in commercial or industrial premises, the correct type to use will depend on compliance with various location-specific codes and standards. You will also need to consider factors such as general operating conditions and environmental factors, as well as any ongoing accessibility requirements.

A sub-distribution board or sub-board is usually a smaller breaker panel acting as a subsidiary to a larger DP. Again, this enables greater control and isolation of a subset of smaller circuits and breakers. A common example might be an RCD Incomer consumer unit, which does not itself have a main switch onboard. This will normally be located on the larger distribution panel that the sub-board is serving.

There are many high-quality distribution board manufacturers and consumer unit suppliers available today. Leading brands we work with to supply our extensive range of commercial and industrial electrical panels include ABB, Contactum, Eaton, ETA, Europa, HENSEL, Legrand, Merlin Gerin, Rose, Schneider Electric, Siemens, and Spelsberg.

All the above are known for building robust, reliable DPs and fuse boards to rigorous specifications and exacting safety standards.