All circuit breakers have the same basic internal and external construction. They all must meet certain construction criteria before they can be sold in the U.S. market place.
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The Basic Construction of a Circuit Breaker
All circuit breakers are enclosed in a very high impact, yet brittle plastic. This plastic is made to withstand high temperatures and insulate high voltages in the 50,000 volt range and higher. The high voltage range is in case your circuit breaker box may take a direct lightening hit. Although the plastic can withstand a high impact hit, it is made to break on the corners so the internal workings does not sustain damage. The internal circuit breaker workings are that of a spring operation, that opens when a piece of conductive metal becomes too hot from over current and weakens to release a trip spring. This trip spring opens a switch. The switch cannot be reset until the conductive metal cools down.
Damage by Over Current
Circuit breakers are manufactured to open whenever an over current situation occurs. Whether it is from a direct, short to ground or a device failure of high amperage. Repetitive over current or constant tripping can severely weaken the conductive metal and finally break the small metal piece. The spring can also weaken and loose its capability to be reset. In this case, the entire breaker must be replaced.
Damage by Constant Use
Circuit breakers should never be used as the on/off switch in any circuit. Constant on/off use will cause the reset spring to become weak and may create a fault that is not recognizable by a tripped switch. Or worse yet, it may not allow the circuit breaker to trip at all and cause a complete and literal melt down of the wiring circuit.
Damage by Impact
Accidentally dropping a circuit breaker on a hard surface such as metal or concrete will pretty much destroy the internal device. Although it may appear to operate fine, there is a great possibility that the spring or conductive metal is damaged. You can never open up a circuit breaker and repair it; it is not worth the risk at any cost.
Damage by Lightening
Circuit breakers are constructed to wit stand a very high voltage, but sometimes a lightening strike may be too much for the internal circuit. A back flow of electricity can also damage the internal works if lightening hits an outdoor fixture and the electricity from the lightening bolt attempts to travel back to the circuit breaker box. This can be identified by either one or many circuit breakers that are tripped and cannot be reset.