How to Install a 240-Volt Receptacle

Learn how to install this common voltage receptacle found in many home appliances.

washer and dryer in narrow room
Photo: Cathy Kramer
Project Overview
  • Working Time: 3 hours
  • Total Time: 3 hours
  • Skill Level: Advanced

Products you use in your home every day—electric water heaters, dryers, ranges, and other large appliances—often use 240 volts. Knowing how to install a volt receptacle is a skill that is sure to come in handy over the life of your appliances. We'll show you how to do it safely and efficiently, and provide pointers along the way. Before you begin, keep the following in mind:

  • There are various 240-volt receptacles, each made for specific amperages and appliances, so be sure to buy the right one for your application.
  • Each appliance needs a separate double-pole breaker.
  • 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.

What You'll Need

Equipment / Tools

  • Voltage tester
  • Drill
  • Saw
  • Hammer
  • Nonconductive ladder
  • Flashlight
  • Groove-joint pliers
  • Screwdriver
  • Strippers
  • Long-nose pliers
  • Lineman's pliers
  • Drop cloth
  • Clamps


  • Fish tape
  • 240-volt receptacle
  • Wire of correct size
  • Greenfield
  • Conduit or NM cable
  • Wire nuts
  • Clamps
  • Double-pole circuit breaker


  1. Clamp Greenfield

    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.

  2. Run to Receptacle

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

  3. Shut Off Power and Attach

    Before installing a 240-volt receptacle, shut off the main breaker. You can check that the power is off by using a voltage tester and testing both plugs. Once you've confirmed the power is off, 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.

  4. Connect to Breaker

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

  5. Strip Wire and Tighten

    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.

  6. Route and Ground Wire

    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.

  7. Connect Breaker

    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.

  8. Connect Wires

    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.

  9. Connect Breaker

    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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