A 220-volt breaker differs from a 120-volt breaker in several ways. The most obvious difference is the size. The 220-volt breaker is twice as thick as a 120-volt breaker. This is because it is basically two 120-volt breakers bonded into one unit. Instead of having one wire attached to the breaker, the 220-volt breaker has two wires attached to it. This large breaker is also made to attach to both power buses in the breaker box at the same time. It draws 120 volts from each side of the box.
Things You'll Need
Turn off the main breaker to make it safe to work inside the breaker panel. Use a screwdriver to remove the screws that hold the breaker panel cover in place and remove the cover. Strip one inch of insulation with wire strippers from the ends of the black, red, white and green wires coming from the 220-volt circuit.
Pull 18 inches of each wire into the box. Attach the white and green wires to the panel by putting them under one of the screws along the long metal neutral bus. With a screwdriver, tighten the screw until the wires cannot be pulled loose from the bus.
Loosen the two screws on the 220-volt breaker. Insert the black wire under one screw. The red wire goes under the other screw. It does not matter which screw receives which wire. Tighten the screws to hold the wires firmly to the breaker.
Clip the breaker onto the power buses. It should make contact with both buses to provide 220 volts of power. Replace the cover onto the breaker panel and use the screws that you removed earlier to attach it. Turn on the main breaker to feed power to the panel and the new circuit breaker.
Never work inside a breaker panel with the main breaker turned on.