Electrical panels & circuit breakers
The municipal electrical supply enters the home or business as two (or three, if there is heavy equipment use) lines of 110 volt ac and one neutral line in a protected box called the electrical panel. The power supply enters the box and is connected to bars to which circuit breakers are attached. If the breaker is attached to one phase, it delivers 110 volts to anything that is attached to it. If the breaker is designed to be connected across both phases, it delivers 220 volts. Neutral lines returning to the panel are connected to the neutral bar, which is connected to a ground.
A circuit breaker is an electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Each breaker is designed to carry a specific load and to break the circuit when the load exceeds that value. Depending on the requirements of the appliances, or total of appliances on the same breaker, typical circuit breakers are 15, 20, 25, 30, and 50 amps. The wiring attached to the breaker leading to the appliances is sized in accordance with the amperage of the breaker.
When the electrical current exceeds the rating on the breaker, it opens the circuit, thereby disconnecting power to the appliance in question. Resetting the breaker is accomplished in one of several ways, depending on the breaker type.
For example, in one type of breaker, it is not obvious that it is off. This breaker is reset by pushing the switch fully off and then on again. One kind of breaker has a window with a red flag when the breaker is off, which sometimes requires waiting up to 30 seconds before the breaker can be reset. One type is off when the tab pops off and must be pushed back in to reset.
When a breaker will not reset, it may be that the breaker is faulty or that the circuit is demanding too much current (overloaded). An overloaded circuit can be the result of too many appliances on one circuit or one that is drawing too much current, a short circuit in the wiring, a faulty appliance, or an unintentional ground.
To troubleshoot, check the appliances on the circuit and ensure that the total amperage does not exceed the rating of the breaker. If it does, remove the extra appliances or wire them to a circuit that can handle them.
If that’s not the issue, disconnect each appliance from the circuit one at a time, resetting the breaker each time. Be sure to tape off disconnected wires and ensure that no bare wires are touching each other. The breaker will stay on when the faulty appliance has been removed.
If the breaker continues to trip, the issue may be in the wiring from the breaker to the appliance.
Visually inspect the wiring for frays or for wires touching each other. If this is not found, turn off the power main and ensure that the breaker in question is still off. Unscrew the wire lug screw at the base of the breaker and pull the load wires from the breaker. Turn the power main back on and reset the breaker. If it continues to trip under a no-load condition, the breaker itself is faulty and must be replaced.
If the breaker does not trip under this no-load condition, then the wiring must need to be replaced. Because a visual inspection didn’t reveal the problem, at this point it is probably best to call an electrician.
Don’t try to repair a faulty breaker. If a replacement breaker cannot be found, check the panel for extras. Often spare breakers are available for replacement. Always replace a breaker with one of the same amperage. It’s OK to use a lower amp breaker on wires designed for higher amps, but only if you know the appliance uses less amperage than the rating of the smaller breaker.
To replace a breaker, turn off the power main. Disconnect the load wires. Place a flat-headed screwdriver on the front top edge of the breaker and pry it out. Find a replacement breaker and replace it in the panel, connect the load wires, and turn on the main service breaker.