Located inside your home is a circuit breaker box or panel that contains
circuit breakers. Some homes have more than one panel. There may be a
main panel plus one or more sub-panels in other locations.
There will usually be a large main breaker at the top of the panel with a
high rating. The breakers for your branch circuits are physically
smaller and have a lower amp rating. Be advised that shutting off the
main breaker will also shutdown the branch circuits, but there is
still high voltage in the breaker panel. The main wire leads into the
panel are still active, and shutting off the main breaker will not
stop current flow to these main leads.
A circuit breaker provides protection for each of your circuits by
stopping the flow of current if an overload occurs. When the load on a
circuit becomes too great, the breaker on that circuit trips and
ceases the flow of current.
The basic circuit breaker consists of a simple switch, connected to either
a bimetallic strip or an electromagnet. In the electromagnetic design,
high current loads will energize the magnet and cause the breaker to
trip. A bimetallic strip design works on the same principle, except
that a high current load will cause the strip to heat and bend. This
trips the breaker.
Another type of circuit breaker is the ground fault circuit interrupter, or
GFCI. These are designed to protect people from electrical shock, as
well as prevent damage to the wiring. Operation is complex, but
basically, a GFCI constantly monitors current flow in the neutral and
hot wires of a circuit. Normally, current flow in both sides will be
equal. If the hot wire connects to ground - somebody accidentally
touches the hot wire, for example - the current level surges in the
hot wire, but not in the neutral wire. The GFCI breaks the circuit as
soon as this happens. Since it doesn’t have to wait for current to
climb to unsafe levels, the GFCI reacts much more quickly than a
conventional breaker.
A breaker that keeps tripping means there is an overload on the
attached circuit. There may be too many devices operating at the same
time, or maybe a short circuit (also called a ground fault). In any
case, proceed with extreme caution. Never, under any circumstance,
replace a breaker with one of higher rating. This is a guaranteed way
to cause overheating of the attached wire. And be careful if you
suspect a short circuit in a device. This can easily injure or kill
you.