Why Circuit Breakers Trip

by Damien Andrews

Circuit breakers are the next generation of fuses. The biggest advantage to a circuit breaker over a fuse is that it can be reset and reused indefinitely. A fuse must be replaced once it’s been blown. Bearing that difference in mind, a tripped breaker is the same as a blown fuse

Contrary to popular belief, circuit breakers are actually simple devices that can only be tripped by one thing: excessive heat. Again, we see the identical principal as that of the old fuses. Fuses are still widely in use, but their applications are generally more automotive and industrial in nature. Your vehicle almost surely has fuses.

If you look at a new fuse and a blown fuse, you can actually see what has happened to make the fuse blow. The wire or metal piece that carries the electricity has been broken, actually melted, thus interrupting the circuit and stopping the flow of electricity downstream. The new fuse will have an intact wire or piece of metal. This is very easy to see in automotive fuses and in the old screw-in types.

Another way to know that it is heat that has tripped your breaker is during the resetting process. When a breaker is tripped it goes to a ‘neutral’ position: not completely off or on. To reset it, you must turn it completely off and then back on. BUT you cannot do this immediately after the breaker is tripped. This is because the breaker is still too hot. You must wait for it to cool down before resetting it. Many people don’t realize this and think they have a faulty breaker and either replace it, or call an electrician. Just wait a few minutes and it should reset just fine.

Circuit breakers have internal mechanisms which react to heat, and ‘break’ the continuity of the circuit when too much heat passes through the circuit. Circuit breakers are rated for allowing different amounts of electricity to pass through them. The rating is in amperes. The most commonly used amperages are 20 and 30.

Sometimes, for 220/240 volt applications, two circuit breakers are linked together to make a 40 or 60 amp breaker. Even larger, when required. Your household “mains” could easily be 100 amp breakers, for example.

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