Distribution board
Central panel dividing power into protected subsidiary circuits.
A distribution board (also known as a panelboard, circuit breaker panel or box, electric panel, fuse box or DB box) is a component of an electricity supply system that divides an electrical power feed into subsidiary circuits while providing a protective fuse or circuit breaker for each circuit in a common enclosure. Normally, a main switch, and in recent boards, one or more residual-current devices (RCDs) or residual current breakers with overcurrent protection (RCBOs) are also incorporated. In the United Kingdom, a distribution board designed for domestic installations is known as a consumer unit.
- field
- Electrical engineering
- known_for
- Dividing electrical power feed into subsidiary circuits with overcurrent protection
- common_enclosure_material
- Sheet metal (North America) or bakelite/wood (older UK fuse boxes)
Lore & Background
North American distribution boards are generally housed in sheet metal enclosures, with circuit breakers positioned in two columns operable from the front. Some panelboards have a door covering breaker handles, but all are constructed with a dead front preventing contact with live parts. Busbars carry current from incoming line conductors to breakers, which are secured with either a bolt-on or plug-in connection. Panelboards are more common in commercial and industrial applications and employ bolt-on breakers; residential and light commercial panels are generally referred to as load centers and use plug-in breakers. In Canadian service entrance panelboards, the main switch or circuit breaker is located in a service box separated from the rest of the panelboard, so that when the main switch is off no live parts are exposed when servicing branch circuits.
Reader's Guide
Distribution boards are essential for safely distributing electrical power in buildings. In North America, they are typically sheet metal enclosures with two columns of breakers and a dead front. Residential panels (load centers) use plug-in breakers, while commercial panels use bolt-on breakers. In the UK, domestic distribution boards are called consumer units, which have evolved from basic fuse boxes with rewirable fuses to modern units with MCBs, RCDs, and RCBOs on DIN rail mountings. Modern UK boards often have live parts enclosed to IP2X even when the cover is removed. The numbering system for breaker positions in U.S.-style boards is universal across manufacturers. Larger commercial and industrial installations use three-phase supplies with subsidiary distribution boards. The design and safety features of distribution boards continue to evolve, with recent UK consumer units split into multiple sections for different types of circuits (e.g., non-RCD for alarms, RCD-protected for sockets and lighting).
Did You Know?
- In North American residential panels, the neutral conductors are secured to a neutral bus using screw terminals, and branch circuit bonding conductors are secured to a terminal block attached directly to the panelboard e
- In the UK, a normal new domestic consumer unit might have from 6 to 24 ways for devices and is split into two or more sections, such as a non-RCD section for alarms and RCD-protected sections for socket outlets and light
- In Canadian service entrance panelboards, the main switch or circuit breaker is located in a service box separated from the rest of the panelboard, so that when the main switch is off no live parts are exposed when servi
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