Many household appliances use 220-volt switches. These switches, commonly found connected to a pool's pump motor and some air conditioning units, connect to four hot wires. Two wires feed the switch and two wires connect to the appliance. The circuits combine two 110-volt wires, called legs, into one circuit, while a 110-volt circuit only uses one 110-volt wire and a neutral wire. A 220-volt switch breaks both legs. If someone wires a 110-volt switch into one leg of a 220-volt circuit, the switch would turn the appliance off but the entire circuit would remain hot and dangerous.
Disconnect the electricity to the 220-volt switch at the circuit breaker box. Find the circuit breaker labeled for the appliance that the switch will connect to and turn that circuit breaker to the "Off" position. When in doubt, turn the "Main" circuit breaker, found near the electric meter, to the "Off" position.
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Cut the wire that feeds the 220-volt appliance in the switch's location with wire cutters. The wire's plastic sheathing will cover two insulated wires, usually colored white and black, and a bare, copper ground wire.
Remove 11/2 inches of both cut ends of the wire's plastic sheathing with a razor knife.
Strip 1/2 inch from each insulated wire with wire strippers.
Wrap both bare copper ground wires around the switch's green ground screw and tighten the ground screw with a flat-head screwdriver. Sometimes the ground screw connects to one end of the switch, and both wires will not reach it. If so, then cut a 4-inch jumper wire, a short piece of wire used for connecting wires, with wire cutters and after stripping both ends, connect one end of the jumper wire to the short ground wire with a wire nut. Connect the other end of the jumper wire to the switch's ground screw.
Push one set of insulated wires into the switch's wire terminals on one side of the switch and tighten the terminal screws with a flat-head screwdriver. The switch will have four wire terminals, two on each side. Each side of the switch will have a gold-colored screw and a silver colored screw. Connect the black wire to the gold screw and the white wire to the silver screw.
Push the second set of wires into the switch's second set of wire terminals and tighten the terminal screws with a flat-head screwdriver. Connect the black wire to the second gold screw and the white wire to the second silver screw.