Changing over a 110 volt outlet to a 220 volt is sometimes needed for an appliance in the home or shop. When working with 110 volt wiring, there are always three wires: black, white, bare. The typical 220 volt outlet would have four wires, one extra wire (red) to carry the additional 110 volts.
You can use three wires safely, but you must ensure that the 220 outlet installed is the only outlet on the circuit. When working with electricity, the utmost care must be taken and you should always consult a licensed electrician before beginning any work.
Turn the main power switch off at the circuit panel. The circuit panel is typically located in the garage or utility room.
Locate and disconnect the wiring from the 110v breaker that is running to the outlet you will be changing over to 220. Disconnect the wiring using the screwdriver to loosen the screws and pull the wiring out.
Locate an open position on the breaker panel to insert and install the 220v 20 amp breaker. Line up the U shaped clamps on the bottom of the breaker and push them down onto the pins on the breaker box until they are locked into place.
Connect the wiring from step 2 (that was connected to the old 110v breaker) using the screwdriver and the following connections: connect the black (hot) wire to one screw on the breaker, connect the white wire to the remaining screw on the breaker, connect the green or bare wire to the ground bus located at the bottom of the electrical panel box.
Remove the coverplate and 110v outlet using the screwdriver to remove the screws holding them in place. Disconnect the wiring from the outlet and discard the cover and outlet.
Attach the black (hot) wire to one brass screw on the outlet and the white (hot) wire to the remaining brass screw. Connect the bare (ground) wire to the green screw on the outlet.
Push the wiring back into the outlet box and using the screwdriver and included screws, mount the outlet to the electrical box and the coverplate over the outlet.
Turn the main power back on at the circuit panel.
You can also install a 220v three-prong outlet with a typical ground, one vertical slot and one horizontal slot. This will ensure that no one is able to accidentally plug in a standard 110v plug into the 220v outlet.
Be sure to wrap red electrical tape around the white wire as a reminder that the wire will now be hot with 110v, and not be confused as a typical neutral wire. Ensure that all wiring meets the building codes for your local area.