Main Panels and Circuit Breakers

Behind the cover of the main panel, power lines connect to the two top lugs of the meter mount. The main breakers pull electricity from the two bottom lugs when the meter is in place to complete the circuit. The main breakers deliver electricity to the two buss bars, which, in turn, pass it along to the secondary circuit breakers. All circuits are connected to a ground (a conductor that is driven into the earth).

A circuit breaker is a switch that may be shut off manually or may be tripped automatically by a failure in the electrical system, usually an overload that could cause the wires to heat up or even catch fire.

The maximum amperage that a service panel may deliver at one time is marked on the main breaker. For most homes, a 100-amp main is sufficient to handle all of the electrical needs; many new home builders now install 150-amp or 200-amp services to insure plenty of capacity. Electrical service panels rated at 60 amps or lower are undersized for contemporary needs.

Every circuit breaker is rated for the type of wire and load required by its circuit. The most typical capacities for lighting and receptacle circuits are 20-amp and 15-amp. Standard circuit breakers for 120-amp circuits take one slot; breakers for 240-amp circuits take two. Some manufacturers make extra-thin circuit breakers that take only half the space of standard breakers.

Larger-capacity circuit breakers are used for electric ovens, electric water heaters, electric clothes dryers, air conditioners and similar appliances that draw a lot of power. Larger breakers may also connect secondary panels-called subpanels-that have their own set of circuit breakers leading to household circuits. Subpanels may be located in a completely different part of the house.

Outdoor, kitchen and bathroom receptacles should be protected by a special ground-fault circuit interrupter (GFCI) circuit breaker to guard against electrocution. Because it is highly sensitive to any short, this type of breaker may need resetting more frequently than standard breakers and should be tested periodically.

MORE ABOUT:
/ Electric meter / / Electrical service / / When lights go out / / Main panel & subpanels /
/ GFCI breakers / / Receptacles / / Switches / / 3-way switches /

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