I use an electric lawn mower, and when I’m cutting the grass in the front yard, I plug the mower into an outlet in my living room.
Once, when I let the grass get a little too high (OK, it was a lot too high), the lawn mower bogged down and tripped a circuit breaker. It was the first time I realized that the outlet by the front door, all the outlets on the west wall of the basement and half the outlets in two of three upstairs bedrooms are all on the same circuit.
I’m not sure who designed that wiring scheme, but the important thing is that I now know where to unplug things when I cut the grass to avoid overloading the circuit.
Knowing which outlets, appliances and light fixtures are controlled by which circuit breakers is important enough that you should take the time to carefully map the circuits in your home.
Mapping helps you manage the distribution of power usage through your house so you can do things like splitting up where you plug your Christmas lights. It also gives you confidence when you need to shut off the power to particular circuits to do things like replacing switches or cutting power to a malfunctioning appliance.
Of course, even when I’m sure that I’ve cut power to the right circuit, I never work on electrical connections without checking with a circuit tester first to be doubly sure the power is off. Like most people, I’m scared to death of getting shocked.
A circuit is a wire loop with electricity continuously flowing through the loop like a circular river. One wire, called the hot wire, carries electricity through the circuit to your lights and appliances, and a second wire, called the neutral wire, carries the electricity back to the service panel, which is the box with the fuses or circuit breakers.
Each fuse in your fuse box and each circuit breaker switch is marked with a number indicating the number of amps allowed on the circuit it controls.
If you know how many amps each of your electrical devices uses, how many amps each of your circuits can carry and which outlets and switches go with which circuits, you can spread things around so you never blow a fuse again.
Circuit mapping goes quickest if you have two people working together–one at the service panel and one moving from room to room checking to see if power is flowing.
Start with floor plan sketches, one for each level of your house. The sketches don’t have to be to scale; they just need to show each outlet and switch and each built-in light fixture and appliance.
Jeff Gutridge, residential manager for Larkin Electric Co. in Dayton, said the easiest way to do a map is to leave the main power switch at the service panel in the “on” position. If you have circuit breakers, turn each of the individual circuit breakers to the off position while leaving the main power switch on. The process is the same with fuses, only you remove fuses to cut power and screw them in to turn the power on.
After cutting power to all the individual circuits, the partner at the service panel then assigns a number or a color to a single circuit and flips the switch or inserts the fuse to power that circuit. The other partner then checks each outlet and switch to see if it is powered.
You can check power at outlets with a circuit tester or simply by plugging in a small lamp. Flip switches off and on to see if the lights they control turn on. Every time the roving partner finds a live outlet or switch, he labels the location of the outlet on the floor plan sketch with the number or color of the circuit of which it is a part.
Once all the switches and outlets for the first circuit are marked on the floor plan, the partner at the service panel removes the first fuse he had put in or turns off the first individual circuit breaker. He then puts in a second fuse or flips on a second circuit breaker, and the roving partner repeats the process of looking for live outlets and switches.
Don’t forget the heavy-duty circuits that control things like washers and dryers. You can tell if those circuits are live by seeing if the washer comes on or the burner on the electric range heats up.
Once you’ve completed marking the floor plan sketches, make at least two copies of them. One set of copies should be stored near the service panel or taped to the inside of the door if they fit there.
Keep another set of copies where you keep your best flashlight and other emergency supplies. Another set should be kept neatly in an envelope where you store your warranties, owner’s manuals and other important household documents.
