Charting Electrical Circuits

Whether you're working with fuses or circuit breakers, it's important to know what switches, receptacles, or equipment are on the circuits they control. In addition, you need to know the basics about how fuses and circuit breakers work. There are many different types of fuses and circuit breakers, each with its own function. The entire purpose of having fuses and circuit breakers is to protect the wiring, not the appliance. Keep this in mind as you chart the circuits, verifying that no fuse or circuit breaker has more amperage than the wire it is protecting. The maximum amount of current a wire can carry, measured in amps, is called load capacity.

While you are working at your fuse box or breaker panel, keep a lookout for any obvious problems. For example, if you unscrew a fuse from a fuse box, examine both the fuse and the shell into which it screws. If you prefer, you may pull and then replace the main for each fuse removal/replacement. Check the fuse or the screw shell for any damage from arcing or burning.

Charting your circuits
Once you are certain that there is no serious damage to your fuse box or breaker panel, you may begin to chart your circuits. A plug-in radio will come in handy, as will an assistant if you can find one. If necessary, you can do the work alone; it will just take a bit longer.

Using a black or blue felt-tip pen, make a scaled floor plan of each room in your home (Fig. 1). Use a separate sheet of graph paper for each space, noting the location of each receptacle, switch, fixture and direct-connect appliance.

Turn off the power
Trip off all of the circuit breakers in your breaker panel or, if you have a fuse box, pull the main and unscrew all of the fuses. In a fuse box there may be two fuses that appear as a main; one is for a large appliance such as a stove or water heater. Read the breaker carefully and test if necessary to be sure the electric is off. Do this during daylight, or use a high-beam flashlight with a spare on hand to avoid working in the dark.

Switch on a circuit
Select a starting point, such as your kitchen; then plug in your radio. Turn the volume up high enough so that you will be able to hear it when you are at the main panel. Switch on the power to only one circuit at a time. If you don't hear the radio, switch that circuit off again, and turn on a different one. Continue this process until you can hear the radio. It may reduce trips if the radio is plugged into the surrounding outlets in the area, while the circuit is still on. Once you can hear it, record the appropriate circuit number on your sketch plan (Fig. 3). Use this method to check every receptacle. For switches and fixtures, you may need an assistant to help you verify whether or not they are on a given circuit. You might also want to write the circuit number on the back of the faceplate.