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Wiring Switches and Outlets

Wire switches and outlets correctly and safely by following the techniques recommended by our two Master Electricians. They show how to avoid the most common wiring mistakes. With these wiring techniques you'll finish faster and guarantee trouble-free electrical performance.

By the DIY experts of The Family Handyman Magazine

Overview: Top ten tips for wiring new switches and outlets

Whether you're replacing an existing switch or outlet or wiring a new one, here are 10 great tips to help you make sure your installation is safe and long lasting. These tips go beyond the basics, so if you're unsure how to begin wiring a switch or an outlet, check out these articles on electrical wiring.

Before you begin any electrical work, always switch off the circuit breaker in the main panel, and then double-check that you've turned off the correct breaker by testing all the wires in the box with a non-contact voltage detector.

Tip 1: Use 4 key tools for safe and fast wiring of outlets and switches

Here are four must-have tools if you plan to wire many switches and outlets:

Voltage tester. You can pick one up for a few bucks and use it to test for hot wires or to find a neutral. Just touch the probes between a hot and a neutral, or between two hot wires. The tester will light up if the wires are “hot.” The tester shown also tests for 240 volts.

Combination sheath and wire stripper. This Klein K1412 (about $23 at home centers and hardware stores) is our favorite. In addition to slots for stripping insulation from 14- and 12-gauge wire, it has slots to strip the sheathing from 14- and 12-gauge nonmetallic cable.

Voltage “sniffer.” The beauty of this tool is that you don't have to touch bare wires to see if they're hot. Just hold it near any wire or cable to see if it's energized. We recommend using a noncontact voltage tester like this to double-check that all wires in a box are “dead” after turning off the circuit breaker. Prices range from about $10 to $22.

GFCI receptacle tester. Just plug it into any GFCI outlet and the lights will indicate whether the outlet is properly wired. Plug it into a GFCI receptacle and press the test button to see if the GFCI is working correctly ($8 to $10).

Tip 2: Tighten loose outlets and switches

In a perfect world, switch and outlet boxes would be flush to the wall surface, but it's not unusual to find them slightly recessed. Switches and outlets mounted to recessed boxes can get wobbly if you rely on device “ears” for support.

To prevent this, slip a coiled-wire shim over the device's mounting screw. The photo above shows how to make a coil from a scrap of insulated wire. Hold the coil against the box to gauge where to cut it to span the gap between the box and the surface of the wall. Slip the coil over the screw and tighten the screw. Your shimmed outlet will be solid and secure.

Tip 3: Use pigtails on outlets

Outlets have pairs of screws on each side that you can use to connect downstream outlets, but it's best not to use them. There are two reasons for this. First, connecting the wires leading to downstream outlets with wire connectors creates a more secure connection. And second, it's easier to press the outlet back into the box if fewer of its screws are connected to wires. Instead, use wire connectors to connect the neutral, hot and ground wires along with 6-in.-long “pigtails.” Then connect the pigtails to the outlet.

Tip 4: Smart switches may need a neutral wire

Switch makers have built all kinds of cool features into modern “smart switches.” You can buy switches with occupancy sensors, timers and programmable dimmers. But the catch is that, unlike an ordinary switch, some of these new switches require a neutral to operate correctly. This is a problem if your old switch is wired as a “switch loop,” such that only a hot and a switched hot are available in the box.

Before you shop for a new switch, remove your old one from the box—after making sure the power is off, of course—and look for a neutral white wire. Any wires connected to the existing switch are not neutral wires. If a white wire is connected to the switch, it should be marked as a hot wire with either a piece of black tape or black marker as shown at right. If there's no neutral in the box, shop for a smart switch that doesn't require a neutral. One of the photos shows a programmable timer switch that requires a neutral.

Tip 5: Choose the right outlet

In an attempt to reduce the risk of electrocution and fires, the National Electrical Code requires specific types of outlets in certain locations. Tamper-resistant outlets are required everywhere, weather-resistant in certain outdoor locations, and GFCIs in areas where dampness or water could contribute to a dangerous shock (kitchens, bathrooms, garages, outdoors). Arc-fault interrupters stop arcing that can cause fires and are required in most living areas. Before you install a new outlet, check the code or consult with someone who's familiar with code requirements to see which type of outlet you should use.

Tip 6: Fold wires neatly

It's surprising how easily an outlet or switch goes into the box if you fold the wires correctly. The trick is to make an “accordion” out of the wires so you can push the device in without crunching the wires. Another advantage of neat folds like this is that they reduce strain on the wires and keep you from accidentally creating a loose connection as you press the device into the box.

Tip 7: Make a tight connection

Most outlets and switches have a strip gauge on the back. Use it to determine the correct length of bare wire to leave exposed when you strip the insulation. If there is no strip gauge, expose 3/4 in. of bare wire. Bend a loop in the wire. Most wire strippers have a hole that you can stick the wire through to bend the loop. Otherwise, use the nose of the stripper or needle-nose pliers. Slip the loop over the terminal screw, making sure it's going around in a clockwise direction. Then pinch the open end of the loop with your stripper or pliers so that it encircles the screw. Finally, snug up the screw. Don't use the “stab-in” holes on the back of the device or stack two wires under the screw.

Tip 8: Match the breakaway tab to the original outlet

There are a few different reasons that an outlet breakaway tab may be removed. If one-half of a duplex outlet is controlled by a wall switch, then the hot tab, and possibly the neutral tab, will be broken off. Or if the top and bottom outlets of a duplex receptacle are powered by two different circuits, the hot tab and possibly the neutral tab will be removed. In any case, when you replace an old outlet, check to see whether the tabs are removed, and if so, break off the tabs on your new outlet to match. Grab the tab with the end of a pliers or your stripping tool and wiggle it up and down to break it off.

Tip 9: Extend short wires

Wires that don't extend much beyond the box are a violation of National Electrical Code requirements. And besides, short wires make it very difficult to hook up your new switch or outlet. Luckily, the fix is simple. Just splice 6-in. pigtails to the short wires. You can connect the pigtails with regular wire connectors, or use in-line splice connectors like the ones shown. In either case, check the label on the wire connector package to see how much bare wire to expose when you strip the insulation.

Tip 10: Don't scrimp on switches and outlets

Better-quality switches and outlets may cost a dollar or two more, but they're worth it. For starters, the components are better. They feel more substantial and will last longer. And an added benefit is that many include a “back-wire” feature, not to be confused with cheap “stab-in” connections, which we don't recommend using. The back-wire feature still relies on the terminal screw to clamp the wire, but you don't have to bend the wire around the screw. Just strip it, push it in and tighten the screw.

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Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

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