Installing a 240-volt Receptacle

Intro

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.

Checklist

Time
About 3 hours to run cable (not including cutting and patching walls) and connect a breaker and receptacle

Tools
Voltage tester, drill, saw, hammer, nonconductive ladder, flashlight, fish tape, groove-joint pliers, screwdriver, strippers, long-nose pliers, lineman's pliers

Skills
Stripping and connecting wires, installing boxes, running cable

Prep
Lay a towel or drop cloth where you cut into walls; cut a pathway for cable.

Materials
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

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Step 1

Choose conduit or Greenfield large enough so the wires can slide easily. Remove a knockout slug from the service panel (make sure it's the right size) and clamp the conduit or Greenfield to the panel.

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Step 2

Run the conduit or Greenfield from the service panel to the receptacle location and attach a clamp. You may need to drill 1-inch holes. The receptacle may be mounted on the floor or in a wall box.

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Step 3

Shut off the main breaker. Fish wires from the receptacle location to the panel. Attach the white wire to the neutral bus bar and the ground wire to the grounding bar.

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Step 4

Connect the red and black wires to the breaker terminals. Snap the breaker into the service panel.

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Step 5

To connect a wire to this type of receptacle, strip the wire end, poke it into the terminal hole, and tighten the setscrew. Fasten the receptacle body to the floor or wall and install the cover.

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Air-Conditioner Receptacle: Step 1

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.

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Air-conditioner Receptacle: Step 2

At the service panel shut off the main breaker. Make room for a double-pole breaker. Connect the ground wire to the ground bus bar and the black and the marked white wires to the breaker. Snap in the breaker.

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Dryer Receptacle: Step 1

Install 10/3 NM cable or run four 10-gauge wires through conduit or Greenfield from the service panel to a receptacle box. Connect the wires to the terminals of the receptacle.

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Dryer Receptacle: Step 2

At the service panel shut off the main breaker. Connect the ground wire to the ground bus bar and the neutral wire to the neutral bus bar. Connect the black and red wires to a double-pole breaker and snap in the breaker.

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