Circuit breaker

How it is used

Often just called a breaker. A breaker 'trips', and you reset it or switch it back on. Types include the MCB (miniature circuit breaker), the MCCB (moulded case circuit breaker) and the ACB (air circuit breaker) used in large panels.

Example sentences

1. The circuit breaker trips every time we start the welding machine.

2. Switch off the circuit breaker for the lighting before you replace the fitting.

Common collocations

• the breaker tripped
• reset a circuit breaker
• miniature circuit breaker
• breaker rating
• switch off the breaker

Related terms

• fuseA safety device with a thin metal link that melts and breaks the circuit when the current is too high. Once it has blown, it has to be replaced.
• overloadA condition in which a circuit, cable or machine carries more current or power than it is rated for over a period of time. Unlike a short circuit, it builds up heat gradually.
• short circuitAn unwanted low-resistance connection between two points that should be kept apart, such as live and neutral. It causes a very large current that can damage equipment or start a fire.
• RCDShort for residual current device: a protective device that switches off a circuit when it detects current leaking to earth, for example through damaged insulation or a person. 30 mA devices are common for protecting people.
• distribution boardAn enclosure that divides an incoming supply into separate circuits, each protected by its own breaker or fuse. In North America it is usually called a panelboard or breaker panel.

More terms: Wiring, Protection and Safety

• ground
• wire
• insulation
• neutral
• electric shock
• lockout/tagout
• arc flash