Electric water heaters, dryers, ranges, and other large appliances use 240 volts. Each appliance needs a separate double-pole breaker. Various 240-volt receptacles are made for specific amperages and appliances. Buy the right one for your application. Some older receptacles use only three wires; codes now call for four wires -- black and red hot wires, a white neutral wire, and a ground wire. Use 12-gauge wire for a 20-amp circuit, 10-gauge for 30 amps, 8-gauge for 40 amps, and 6-gauge for 50 amps. Check local codes for requirements. Work with extreme caution: 240 volts can cause serious bodily harm.
About 3 hours to run cable (not including cutting and patching walls) and connect a breaker and receptacle
Voltage tester, drill, saw, hammer, nonconductive ladder, flashlight, fish tape, groove-joint pliers, screwdriver, strippers, long-nose pliers, lineman's pliers
Stripping and connecting wires, installing boxes, running cable
Lay a towel or drop cloth where you cut into walls; cut a pathway for cable.
240-volt (or 120/240-volt) receptacle, wire of correct size, Greenfield, conduit or NM cable (if allowed), wire nuts, clamps, double-pole circuit breaker
A large-capacity window air-conditioner calls for a 20-amp, 240-volt receptacle. Route 12/2 cable from the service panel to a receptacle box. Mark the white wire black. Connect the white and black wires to the receptacle terminals. Connect the ground wire.