Distribution board

Consumer units

In the United KingdomBS 7671 defines a Consumer unit as ” A particular type of distribution board comprising a type tested coordinated assembly for the control and distribution of electrical energy, principally in domestic premises…”[5] These installations usually have single-phase supplies at 230 V (nominal standard) and historically they were known as fuse boxes as older consumer units used fuses until the advent of mini-circuit breakers (MCBs). A normal new domestic CU used as a main panel might have from 6 to 24 ways for devices (some of which might occupy two ways), and will be split into two or more sections (e.g. a non-RCD section for alarms etc., an RCD-protected section for socket outlets, and an RCD-protected section for lighting and other built-in appliances). Secondary CUs used for outbuildings usually have 1 to 4 ways plus an RCD.

Recent (pre-17th edition wiring regulations) CUs would not normally have RCD protected sections for anything other than socket outlets, though some older CUs featured RCD Incomers. Before 1990, RCDs (and split busbars) were not standard in CUs.