Most appliances that run on 220-volt power draw 30 amps or more of current, but some, such as small air conditioners, certain power tools and some kitchen appliances, draw only 20 amps. If you need to install a 20-amp, 220-volt outlet, which is equivalent to a 230-, 240- or 250-volt outlet, you need to be familiar with 220-volt wiring. It differs from 110-volt wiring by requiring an extra hot wire that must be connected to a separate circuit breaker coupled to the breaker controlling the other hot wire.
While the wiring procedure for a 220-volt outlet is straightforward, consider hiring an electrician to install the breakers for the circuit. Working in the breaker panel is dangerous, and you can get a fatal shock if your tool slips or you touch something you shouldn't. The job of installing the breaker includes connecting the circuit wires.
What Does a 20-Amp, 220-Volt Outlet Look Like?
A 220-volt, 20-amp outlet looks like a 110-volt one but with one key difference. It has three slots, including a semicircular one for the ground pin, but the two other slots aren't vertical – they're horizontal. On the side of the outlet, you'll see two connection screws. They are both brass, which means they are for hot wires. A 220-volt circuit doesn't need a neutral wire. A neutral is usually provided on outlets with larger current ratings to power auxiliary 110-volt devices, such as clocks and timers, but a 20-amp plug doesn't need this functionality.
Choosing Cable for a 20-Amp, 220-Volt Outlet
You need 12-gauge cable for a 20-amp circuit no matter whether the circuit is 110 or 220 volts. You won't be using a neutral wire, so the cable should have only two hot wires, which are red and black, and a bare ground wire. You might not be able to find cable that meets these specifications, so you have two options. One is to purchase 12 AWG, three-conductor cable and simply don't use the white wire. The other is to use conventional 12-gauge, two-conductor cable with ground and mark the white wire on both ends with red paint to indicate that it's a hot wire.
Run the cable between the outlet box and the panel. This can be an easy job or a more challenging one depending on the length of the run and the number of floors between the panel and the outlet. In most cases, it's best to run the cable laterally through the basement or crawl space and feed it vertically through the wall to the outlet. All 220-volt wiring is to a dedicated circuit breaker, which means you can't tie into another circuit.
Wiring a 220 Plug
At the panel, the two hot wires should be connected to a double-pole, 20-amp circuit breaker, and the neutral wire should be connected to the neutral bus. After you (or an electrician you hire) finish this, make sure to keep the breaker off until you finish hooking up the outlet. There's no problem wiring the outlet first and hooking up the breaker afterward if that's what you prefer.
Connect the hot wires to the two brass terminal screws on the plug. The wires are interchangeable, so you can attach either one to either screw. To make a secure connection, strip 1/2 inch from the end of each wire and bend the wire clockwise before hooking it onto the screw. That way, the screw will draw the wire toward the terminal when you tighten the screw. If you bend the wire the other way, tightening the screw will force the wire off the terminal.
Once both hot wires are connected, attach the ground wire to the green ground screw, and then push the wires into the box and screw the outlet to the box. Finish off by installing a cover plate.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.