All household members should know where the main power switch is located, in case of an emergency such as a fire or basement flooding. Even though it is not required, the most logical place for that main switch is at the main panel. Sometimes, however, the main switch is located in a separate box, even at a separate location.
Some older homes have fused pull-outs; others have a lever that you pull to shut off the main power. In the latter case, you also have to pull that lever to change a fuse, which protects you as well. Still others have a circuit breaker switch or button. Whatever the set-up of your power panel, you will be able to operate the main switch without being exposed to live electricity.
Keep in mind how dangerous it is to work at the breaker box if the main switch is not turned off. The amount of electricity being brought into the house can easily kill. If you are unfamiliar with your box, or if you don't know where the main switch is located, have a professional explain how to work with your particular box.
Circuit breakers are protective devices that control the power going to a particular route of wiring. In case of an overload or a short on that circuit, the breaker trips and automatically shuts off power to that circuit.
Ground fault circuit breakers offer protection against more than just overloads. Many areas require these for outdoor wiring, or for rooms with outlets exposed to moisture, such as bathrooms and kitchens. Ground fault circuit breakers are also recommended for workshops and areas where power tools are in use.
Placing new breakers into the circuit box is an easy enough matter, providing you have room in the box to accept new breakers. If not, you will have to have an electrician install a new, larger circuit box or a secondary box.
Begin by turning off the power at the main circuit breaker switch. Remember, the box is still hot above the main breaker, so don't touch the wires above this disconnect. Again, be absolutely certain that this switch does indeed cut off the power into the circuit breaker box. Bring the neutral and grounding wires into the box and attach them to the "neutral bus bar." Do this by sticking the stripped ends of the wires into any hole in the neutral bus bar and attaching them by tightening down the screw heads.
Note: Some boxes will have two bus bars, one for the ground wire, one for the neutral. Others will have only one bus bar for both neutral and ground.
Hook up the circuit breaker switch to the black hot wire by tightening. Typical breaker box anatomy. Screw in the breaker over the wire, as previously described. Now it is a simple matter of snapping the breaker back into position in the box and turning the main switch back on. Then turn on the circuit switch that will feed electricity to this new circuit.
Use a voltage tester to check if electricity is present at the outlets. One prong is inserted into the hot side of the outlet and one into the neutral or ground side. If the wiring is right, the bulb will light up. (This device can also be used to test a faulty receptacle prior to replacement.) Be sure to touch only the insulated wire. Never touch any metal parts.