Learn Them All in Minutes: Six Essential Wiring Skills

It's essential to know how to shut off all electricity to your home. By turning off individual circuits at the main service panel, you can work safely on any receptacles, lights and appliances in your home. Cutting the power is always useful when there's a gas leak or other emergency.

First, find the main service panel. It's probably located on an exterior wall near the point at which power lines enter your house. Look for wires running from a telephone pole to the weatherhead near the eaves. You'll probably see a 2- or 3-inch conduit running down from it into the panel. Panels are also found in attached garages and, especially in older homes, in basements.

Next, open the panel door. In a newer home or one that's had its service upgraded, you'll see circuit breakers, which look rather like large light switches. (If yours is an older home, you may see cartridge or screw-in fuses.) Most newer panels have two large breakers at the top and a column or two of smaller breakers for individual circuits.

Now to shut off a circuit. If you're lucky, you'll find a chart inside the panel door that identifies the area each breaker controls. Most of us, alas, will have to find the target circuit by trial and error.

Here's how to turn off circuits in your wiring

1. Have a helper test circuits in the room where you'll be working, while you stay at the entrance panel. Your helper can flip light switches or plug a voltage tester into receptacles to see if the power's on or off.

2. Switch off breakers or unscrew fuses in the main panel until the tester's light (or the fixture controlled by the switch) goes out. As you identify each room or circuit, label the breaker (or fuse) that controls it.

3. To be safe, completely remove the fuse from the panel, or tape the breaker in the OFF position while you're working on the circuit.

4. To turn the power back on, simply flip the breaker from OFF to ON (or replace the fuse).

Safety: The lights in a given room may be on a different circuit than the receptacles, especially in an older home or any home where wiring changes have been made over time. Don't assume that, having found the breaker for one device in a room, you've found them all. Always test a device before you work on it, and be sure the power is off.

Never assume that the power to a fixture, receptacle, or circuit is off.

Testing for a live current.

Always test an electrical device before you begin working on it. The easiest, least expensive way to do so is with a voltage tester, shown here. If you don't have one, buy one. It can save your life. To use a voltage tester, simply plug its leads into a receptacle, or, if the cover plats off, touch them to the screw terminals of the device. (Be careful not to touch the bare-metal leads themselves, however, or you may get shocked.) If current is present, the tester will light. Also touch one tester lead to the grounding wire or grounding screw, and the other lead to each socket, wire, or terminal in turn.

If you are working in an open electrical box, such as the ceiling box shown here, touch the voltage tester leads - carefully - to all possible wire pairs you find within, and to the box itself. When you're done, you will know whether it is safe to keep working--or whether it is time to go back to the main service panel, find the circuit that's still on, and shut it off.

Testing for continuity

The continuity tester has a battery in it, so it can apply a low-voltage current to devices and circuits even when the main power is off. This tool lights up when continuity - a complete circuit, in other words - is detected. Use it to identify which wire is sending current where and to find breaks in circuits. The best models sound a tone and/or vibrate, allowing you to keep your eyes on the probe tips as you work.

Tip: Keep a variety of sizes of twist-on wire connectors on hand. The two most commonly used sizes are color-coded yellow and red. Note: All electrical connections must be housed in an approved work box, and all electrical cables must be anchored to an electrical box, and nailed to framing within 6 inches of the box.

Safety: It's unsafe to extend a circuit by splicing a thicker-diameter wire onto a thinner one. Someone unfamiliar with the extension may assume that the entire circuit is of the heavier wire and overload it.

Old House: The knob and tube wiring typical of an old house often has many soldered splices wrapped with electrical tape. These splices are common in attics and basements, and they're usually safe if left undisturbed. If your local code permits you to tie into a knob-and-tube circuit, however, you must make the connection in a junction box.