Frequently, we hear the following terms used interchangeably: breaker and fuse.  They are similar in that are both electrical overload protection devices, but they work differently.

 

Breaker

78ef6701-2662-4ac1-a2e1-a0e58a25fc49_400Circuit breakers are reusable overcurrent protection devices. After tripping to shut off (“break”) the circuit, the breaker can be reset to protect the circuit again. A circuit breaker is a multiple-use device. It is usually permanently installed in equipment and it generally has two mechanisms for breaking the current: (1) a magnetic portion which opens with a large current, and (2) a thermal part that also opens under overcurrent

The thermal part has a lag so these typically react slower, but with very high currents the magnetic part will open quickly. The circuit breaker usually has a button or handle to reset it after it has cooled down.  Circuit breakers are usually more costly and larger than fuses.

 

 

Fuse

170px-Tektronixoscilloscope442backfuse-ccbysawikipediaThe fuse is also a reliable overcurrent protective device, primarily used as a circuit protection device for overcurrents, overloads and short-circuits. Its safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.  Because it melts and breaks, it is one-time use and it has to be replaced when it blows.

There are many different types of fuses for residential and commercial use, but the most common type is made up of a metal wire or filament that is enclosed in a glass or ceramic/metal casing. In a home, the fuse is typically plugged into a central fuse box where all the building’s wiring passes through. When the electricity is flowing normally, the fuse permits the power to pass across its filament, between circuits. If an overload occurs, the filament melts, stopping the flow of electricity.

Are there any electrical terms you’ve heard that you don’t understand?  Check out our reference page for common electrical terms defined.