Just about anyone can do basic home wiring. If you’re careful about connections and follow a few commonsense safety tips, wiring is among the most predictable, pleasant parts of construction. And you’re never long in doubt whether you’ve wired things correctly. If you goof, a fuse or a breaker trips harmlessly; if you do it right, bulbs shine and radios play.
Take a few minutes to review the essential wiring skills shown below. Even if you’re an old hand at home improvement, chances are you’ll find a useful tip you haven’t seen before. If you’re a beginner, these how-tos will set you on the right path in a hurry.
It’s essential to know how to shut off all electricity in 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 find the target circuit:
- 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 (tons of those on Amazon) into receptacles to see if the power’s on or off.
- 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.
- 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.
- 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.
When you need to make electrical repairs, use an inexpensive adjustable wire stripper (check at Amazon) like this. It adjusts to fit most common wire gauges and makes wire stripping simple and reliable.
Set the opening no smaller than the wire’s diameter so you won’t nick and weaken the wire. Typical house wiring is 12- or 14-gauge (which is thinner than 12-gauge). You’ll likely find these wire sizes–and many more–marked on the tool.
Stripping wire is a simple 1-2-3 operation:
- Set the wire stripper opening to the proper size, and place the wire in the jaws with about an inch of wire protruding.
- Squeeze and twist the stripper around the wire to cut through the insulation without cutting into the wire itself.
- Pull off the insulation.
Safety: Be careful not to nick a wire. Even if the wire doesn’t break, a cut reduces its diameter and thus its capacity to conduct electricity. This is dangerous and could lead to an electrical fire.
Never assume that the power to a fixture, receptacle or circuit is off.
Testing for 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 (here is Amazon’s best choice). 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 plate is 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.
Testing a receptacle
If you’re 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’ll know whether it’s safe to keep working–or whether it’s 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 (check on Amazon) 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.
Attaching a wire to a screw terminal is a skill you’ll use in lots of electrical projects. You’ll find screw terminals in most electrical devices: lights and light switches, plugs and receptacles, appliances, and the like. Here’s the right way to connect a wire to a terminal, safely and securely.
- Bend a stripped wire end into a 180-degree loop with long-nose pliers. (If you bend around the pliers’ nose, the outer curve creates a perfect “U” that fits right over the shank of a screw terminal.)
- Place the wire on the screw, wrapping the wire clockwise so that it stays in place as you tighten the screw; then crimp it in place with the pliers.
- Tighten the screw terminal, pulling the wire gently so that “U” stays in contact with the screw shank. Be sure that there’s no insulation under the terminal.
Tip: Don’t overtighten screw terminals or you’ll strip their threads. If you’re uncertain how much pressure to apply, hold the screwdriver at your fingertips, not in your hand, as you tighten screws. That way, it’s almost impossible to strip a screw thread.
Connecting wires in an electrical box is a common task worth mastering. The good news is that mastery takes only a couple of tries. Your finished connections will be professional, and, most importantly, safe.
- Strip each wire back about 3/4 inch.
- Hold the wires together with their tips even. You don’t need to twist the wires together before you install the twist-on wire connector; in fact, wire-connector manufacturers recommend against it.
- Slip a twist-on wire connector over the ends of the bare wires and turn it clockwise until it’s tight. There should be no bare wire showing outside the connector. (If the sheathed part of the wires twists slightly below the wire connector, no problem. The bare wire ends will be held securely by the connector.)
- Pull gently on the wires to be sure they’re all securely fastened.
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.
When it comes to stuffing wires and devices like switches and receptacles into electrical boxes, don’t just jam them in willy-nilly. It’s important to be gentle but firm and to fold the wires into the box neatly. Here’s how:
- Make sure the power’s off, and test it to be sure.
- Straighten the wires and clip them to approximately the same length. If you’ve merely replaced, say, a switch, just attach the wires and pull the switch out gently to straighten the wires.
- As you press the device back into the box, carefully fold the wires in a zig-zag fashion. You may need to help them fold by prodding them with the blunt end of a tool. Line up the mounting screws with the box threads.
- Tighten the mounting screws and attach the cover plate.
- Turn on the power and test your work.
Tip: If the outlet box is too deep in the wall, fur out the switch or receptacle by stacking No. 6 washers on the fixture mounting screws. Or extend the box itself with a good ring.