MCB (Miniature Circuit Breaker)

A resettable switch in the consumer unit that automatically disconnects a circuit when the current exceeds the safe rating (overload) or when a short circuit occurs, replacing older rewireable fuses. MCBs are rated in amps (e.g. 6A for lighting, 32A for a ring circuit) and must be the correct rating for the cable they protect. A tripped MCB that immediately trips again after resetting indicates a fault requiring investigation by a qualified electrician.