Wiring a Dryer Receptacle

It's been said that the first electric dryer was invented one rainy day when a homemaker strung a clothesline in front of the TV set during a presidential debate. So, having exhausted our supply of dryer jokes, let's get on with wiring them safely, which is easy enough if you follow a few simple rules and do the work in the proper sequence.

What a Dryer Needs in Life
To wire a dryer properly, you must understand that it needs not 120 volts, not 240 volts, but both 120 and 240 volts. To transfer this voltage from service panel to dryer receptacle, you need a cable that has two hot wires (red and black), one neutral wire (white), and a grounding wire (green or bare copper). The dryer receives 240 volts of current through the red and black wires; the electric heating element needs both wires to heat up. The dryer then selects one of these two wires it makes no difference which and uses it along with the neutral wire to obtain the 120 volts it needs to power the timer, buzzer and so forth. The ground wire connects to the appliance frame so that, in case of a hot-wire-to-appliance-frame short circuit, there's a current path back to the service panel to trip a breaker or a plug or cartridge fuse.A typical dryer uses about 4,500 watts of energy. This translates to about 20 amps. Heavy-duty dryers can pull slightly more; light-duty, slightly less.

Picking the Wire Gauge
The higher the current flowing through a wire, the larger the wire gauge (diameter) must be. Since a dryer pulls about 20 amps of current, you'll need a wire gauge capable of handling at least that amount of current, if not more. Most household utility circuits have 12-2 cable W/G (12-gauge wire, two conductors hot and neutral with ground). But since the maximum load a 12-gauge wire can carry is 20 amps (and even less under certain conditions) your dryer circuit should be wired with 10-gauge. Ten-gauge wire can carry a maximum of 30 amps. Specifically, ask for 10-3 NM-B cable W/G (10-gauge wire, three conductors, with ground).

Picking a Dryer Receptacle
The dryer receptacle must match the electrical requirements of the dryer. Simply put, the receptacle must be listed for 120/240 volts, have internal slots for three conductors plus ground, and be rated for at least the amount of current flowing through it. Typically, a receptacle that meets these requirements has two big slots side by side to accept the red and black wires, one L-shaped slot that wires into the neutral, and a ground slot. Its maximum current rating is 30 amps. But you don't have to remember all these specs just ask for a new-style dryer receptacle, the one with four slots. The old-style had the neutral and ground together and so had only three slots on the receptacle face: hot, hot, and a combined neutral/ground. That configuration is no longer up to code.

Safety Code requires that dryers must be on their own dedicated circuit. Always completely finish wiring a dryer receptacle before you wire its cable into a circuit breaker. Never wire the breaker first and think you're safe in wiring the receptacle because you have the breaker turned off someone may inadvertently turn the breaker on while you're handling the wires.

Wiring the Receptacle
A few words about running 10-3 cable: It's so stiff that routine tasks like fishing cable become major undertakings. But here are four quick tips to speed the task.

• When you drill holes to run cable through framing, use a chalk line to line up holes, and drill as perpendicular to the studs or joists as possible. A right-angle drill will help you do that; use a 1-inch bit.
• To reduce friction, soap the holes liberally. Bar soap or dishwashing liquid are fine.
• Easier yet, you may want to chisel out corners instead of drilling holes and not have to pull cable at all. But you'll need to protect the cable by placing nail plates over the slots you cut.

So, with a new four-slotted dryer receptacle in hand and 10-3 W/G cable coming into the space right behind the dryer, you're ready to wire the receptacle. First attach the receptacle to the floor or wall. Pick a place to mount the receptacle that won't interfere with the dryer's sliding into its final location and that will allow you to unplug it easily. Even the pros sometimes forget this latter point, which makes a contortionist out of anyone who later has to unplug that dryer.

Once you've fixed a location for the receptacle, take the cover off the receptacle and screw its metal base onto the floor or wall. (It's best if you find a stud and screw into that.) The manufacturer has provided two screws just for this purpose and you should throw them into your miscellaneous screw jar. Instead of the pan-head, slotted screws the manufacturer gives you, shoot in two hex-head screws using your cordless drill. That's what the pros do, anyhow and it's much faster and far less tedious than hand-screwing the receptacle base.

Once that the receptacle is secure, you're ready to feed in the cable and attach its wires to the terminals in the receptacle. Now it's time to wire the dryer.

Step by Step
1. Strip about 6 inches of sheathing off the cable and feed it through the receptacle clamp. Gently tighten down the clamp, making sure that the section of cable gripped by the clamp is still sheathed.

2. Bend the individual wires so that they align to their slots. Typically, printing on the receptacle base tells you which colored wire goes where. It makes no difference which colored hot wire goes to which slot, however there is no polarity.

3. Once you've aligned individual wires to their respective terminal slots, cut them to length. The receptacle cover leaves little room to fold wires, and 10-3 is quite stiff, so keep wire as short as is feasible. Then strip about 1/2 inch of insulation off the end of each wire.

4. Push each bare wire end down into its slot. To do this, you may first have to loosen the screw-tightening mechanism in the slot and swivel it up and out of the way. Once the wires are in, swivel the mechanism back into place and tighten the screws down onto the bare wire ends.

5. Put the cover back onto the receptacle, tighten the long attachment screw that holds the cover to the base and you're done. Go forth and dry.

TOOLS AND MATERIALS
Wire stripper
Dryer receptacle
Cordless drill/driver
10-3 NM-B cable with ground