Electrician Job Question:
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What does a fuse or breaker do? What are the differences?

Answer:

Fuses and circuit breakers are designed to interrupt the power
to a circuit when the current flow exceeds safe levels. For
example, if your toaster shorts out, a fuse or breaker should
"trip", protecting the wiring in the walls from melting. As
such, fuses and breakers are primarily intended to protect the
wiring -- UL or CSA approval supposedly indicates that the
equipment itself won't cause a fire.

Fuses contain a narrow strip of metal which is designed to melt
(safely) when the current exceeds the rated value, thereby
interrupting the power to the circuit. Fuses trip relatively
fast. Which can sometimes be a problem with motors which have
large startup current surges. For motor circuits, you can use
a "time-delay" fuse (one brand is "fusetron") which will avoid
tripping on momentary overloads. A fusetron looks like a
spring-loaded fuse. A fuse can only trip once, then it must be
replaced.

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