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How to Wire in a 30 Amp 220 Outlet

Jerry Walch

Wiring a 30-ampere, 220-volt receptacle is a straightforward project, assuming that the 3-conductor w/gr. cable and device box is already in place. The 1999 Revision of the National Electrical Code (NEC) requires all newly installed 30-ampere, 220-volt receptacles to be of the 3-pole, 4-wire type. A 3-wire, 3-pole receptacle can no longer be installed because the system neutral wire is no longer permitted to double as the equipment-grounding conductor.

An electric clothes dryer needs a high voltage outlet.
  1. Turn the branch circuit breaker off and secure it in the off position before beginning this project.

  2. Remove 3/4 inches of insulation from the ends of the wires.

  3. Insert the red and the black wires under the "X" and "Y" compression screws and tighten the screws securely down on them.

  4. Insert the white, neutral wire under the "Z" compression screw and tighten the screw securely down on it.

  5. Insert the green insulated or bare copper grounding wire under the "Grn" compression screw and tighten the screw securely down on it.

  6. Tug on all the wires to make sure they are secured tightly under their compression screws. Loose connections allow arcing faults to develop which can cause the insulation and any surrounding combustible material to catch fire. Loose connections, besides being a fire hazard, cause a high resistant connection to develop and that in turn causes a voltage drop to develop at the connection, robbing your appliance of needed voltage.

  7. Push the receptacle into the box being careful to not pinch any of the wires between the receptacle and the metal box. Installing a 30-ampere, 220-volt, 3-pole, 4-wire receptacle in a standard device box is a tight fit so it's easy to pinch and damage the insulation on the wires if care isn't used.

  8. Secure the receptacle in the box with the 6-32 screws that came with the receptacle. Make sure that the receptacle is straight and centered properly in the box before tightening the screws completely.

  9. Install the receptacle cover plate. Turn on the branch circuit breaker.