A 220-volt circuit supplies twice the voltage of a standard one. The holes of the receptacle, as well as the prongs on the plugs of appliances you use in these circuits, are configured differently so that you can identify them. The receptacle for a 15-amp 220-volt circuit looks almost the same as that for a standard 110-volt grounded circuit, except that the flat prongs are horizontal instead of vertical. You need two hot wires to power it, so if the circuit is already installed, make the white wire hot and connect it to a separate circuit breaker.
Things You'll Need
15-amp, 220-volt receptacle
Red electrical tape
15-amp double gang circuit breaker
Turn off the power to the circuit by shutting the breaker off in the panel.
Disconnect the old 110-volt receptacle, if there is one. Remove the outlet cover, unscrew the receptacle from the electrical box and disconnect the wires by loosening the screws with a screwdriver. If the wires are inserted into holes behind the screws, snip them with wire cutters. Strip ½-inch off the ends of the black and white wires with a wire stripper.
Prepare the circuit wires if an outlet is not already connected to the circuit, by removing sheathing from the cable with a utility knife and stripping ½-inch of insulation from the black and white wires.
Connect the black and white wires to the two brass terminals on the outlet. Wrap red tape around the white wire to signify that it is now a hot wire. Connect the ground wire to the ground terminal. Push the wires into the electrical box, screw the outlet to the box and screw on the cover plate.
Turn off the main breaker in the panel and pry off the circuit breaker that was controlling the circuit. Remove the black wire by unscrewing the lug and pulling it out. Remove the white wire from the lug to which it is connected on the neutral bus of the panel and wrap red tape around it. Be careful while working in the panel. Use insulated tools and don't touch the brass or copper bus bars. They are hot and can deliver a fatal shock.
Connect the black and white (now red) wires to separate terminals on a double-gang 15-amp circuit breaker. Turn the switches off and snap the breaker onto the panel anywhere two adjacent slots are available. Identify the new circuit on the cover of the panel and flip the switches back on.
Because the breaker for the circuit is rated for 15 amps, you may use 14-gauge wire. It is a good idea, however, to use 12-gauge wire, which is thicker and less prone to overheating.
It is dangerous to work inside an electrical panel unless the power to it has been shut off. Turning off the main breaker does not do this. If you do not feel confident enough to make connections in the panel, do not hesitate to call an electrician.