Introduction
Unlike old-fashioned fuses, circuit breakers can be reset without replacement. But it is still important to check for trouble in the circuits they control.
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Anatomy of a circuit breaker
Think of a circuit breaker as a heat-sensing switch. As the illustrations at right show, when the toggle is on, current flows through a set of contacts attached to a spring and lever. The contacts are held together by tension in the bimetal strip through which the current flows.
If there is a short or an overload in the circuit, the bimetal strip heats up and bends. As it bends, it releases a lever that opens the spring-loaded contact. The contact remains open until the toggle is manually reset by the homeowner.
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Identifying a tripped breaker
A tripped breaker will identify itself in any of the four ways shown at right. To find out whether the problem has corrected itself, reset the breaker. If the problem persists, the breaker will shut itself off again. Usually the problem is an overload, and you only need to unplug or turn off one of the circuit's big energy users. If the circuit breaker keeps tripping even though it isn't overloaded, suspect a short. A defective plug, cord, or socket may be the problem.
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Checking connections in boxes
Short circuits can occur in electrical boxes. Here, a wire has pulled loose from the switch and has shorted out against the box.
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Inspecting wiring
Frayed or nicked insulation will expose wire and could cause a short. Wrap damaged insulation with layers of electrical tape.
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Identifying overheated fixtures
High-wattage bulbs can melt insulation. Never use bulbs with higher wattage ratings than those for which the fixture is rated.
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