Things You'll Need
Voltage line tester
Wiring a 220/240-volt outlet will allow you to run many of today's heavy appliances or garage tools. The 220 volt, or as it's called today, 240-volt outlet, will carry twice as much current as a typical 110-volt outlet used in the home. Working with electricity can be dangerous and extreme care should be taken when working with or around electrical lines. Knowing how to wire a 240V electrical outlet is critical to completing the project correctly and safely. Be sure to contact a licensed electrician before beginning any work.
Turn off the power to the outlet to be changed at the main circuit panel. Use the voltage line tester, following the manufacturer guidelines for that model, to ensure no power is reaching the outlet.
Using the screwdriver, remove the cover plate screw and cover plate over the outlet.
Using the screwdriver, remove the screws that are holding the outlet inside the electrical box. Once loose, pull the outlet out about 3 to 5 inches, or as much extra wire will come out of the box. This will allow easier access to the outlet.
Using the screwdriver, unscrew the screws that are holding the wires to the back of the outlet just enough to loosen them and remove the wires. Discard the outlet.
If needed, cut any bad ends off the wires and strip about 1 inch of insulation away with the wire cutters/strippers.
To connect the wiring to the outlet, follow the proper method, based on if you have three wires or four wires.
Four wires (preferred method): Using the screwdriver, connect the ground/bare wire to the screw on the bottom of the plug which is usually also green. Connect the white (neutral) wire to the center or silver screw. Connect the remaining wires black and red which will both be "hot" wires to each of the top two screws on the outlet (brass or gold colored).
Three wires: Using the screwdriver, connect the green/bare wire to the green screw on the bottom of the outlet. Connect the white and red/black wires to the top two screws on the outlet.
Tighten each screw to a snug fit.
Using the screwdriver and the screws, mount the outlet back in the electrical box. Also, mount the cover plate back over the outlet.
Turn the power back on at the breaker in the main circuit panel. Using the electrical line tester, and following the manufacturer guidelines for that model, test the outlet to make sure that power is reaching the outlet.
Never attempt to work on any outlets or electrical lines without making sure the power is turned off. Electricity can be fatal, and extreme caution should always be used.
Be sure to follow all electrical building codes relevant to your area.