Home Electricity: How Circuit Breakers Protect

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Circuit breakers that trip and shut the electricity off to an outlet are doing the job they were designed for. If so, you’re probably making a trip to the circuit breaker panel,locating the tripped circuit breaker and resetting it. Dealing with a tripped circuit breaker is the the last thing you want to happen when it’s dark and cold outside. Like their predecessors, the fuse, circuit breakers are designed to automatically turn off the electricity to an overloaded circuit.

Circuit breaker panels are located near the point of where the electrical service lines enter into your home or office building. Inside the panels are two or more stacks of circuit breakers, each one protecting an electrical circuit, or “load” from electrical surges or overloads. Because electrical current demand, or load, varies according to the intended use of an particular circuit, circuit breakers will vary in porportion and current rating.

Circuit breaker panels can also include Ground Fault Interrupter circuit breakers that protect circuits in
the kitchen and bathroom. Ground Fault Interrupt Circuit are now required for electrical circuits that service kitchen and bathroom circuits where a sudden electrical short circuit has a greater possibility of happening. While they are now required in all newly constructed homes, it’s a good idea to check with the municipal building code officer for up-to-date practical knowledge.

In the event of an electrical short circuit or overload, a circuit breaker “breaks” the circuit by quickly cutting off the electricity to the circuit. Inside the circuit breaker are a bi-metal strip, a set of contacts through which the electrical current flows, and a spring. The bi-metal strip will hold the contacts together as long as the flow of electrical current remains within safe levels. As long as the current flow remains at or below the breaker’s rated current level, the strip won’t bend and the contacts remain together. If the current flow is sufficient to cause the bi-metal strip to heat up and bend, the breaker trips and the contacts are pulled apart by the force of the spring thereby stopping the flow of electricity.

Once the electricity has stopped flowing, the bi-metal strip cools down and returns to its original shape. Resetting the circuit breaker now reestablishes the circuit through the contacts. Circuit breaker panels should be tagged to show which breaker is protecting a particular circuit. A tripped breaker can also be identified by the location of the toggle or a red indicator appearing in a small window on the breaker.

Together, these two devices are the best protection against dangerous electrical shock. GFIs can be periodically tested for proper functioning using a test and reset switch located on its face.

Circuit breakers have saved countless numbers of lives and prevented fires in as many homes and buildings. They should never be bypassed. Generally speaking, they will last for decades, with only an occasional failure. If, however, a circuit breaker should fail, you can replace it yourself following sound electrical safety precautions.

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