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How Receptacles are Wired

Most receptacles have two outlets (duplex receptacles) and are rated at 15 or 20 amps, 120 volts. One or both outlets may be electrically live at all times, or one or both may be controlled by a wall switch. The receptacle may be installed in the middle or at the end of a circuit. The wiring arrangement is different in each case.

Receptacles have three different-colored terminal screws:

  • Brass screws are hot.
  • White or silver screws are neutral.
  • Green screws are for grounding.

Receptacles may be grounding or non-grounding types. Always replace a receptacle with a grounding type unless there's no grounding wire in the box or the box isn't grounded, then you can use a non-grounding receptacle. To install a grounding receptacle to an undgrounded box, you must ground the receptacle independently. For help, consult a professional.

Because receptacles are rated for a specific amperage and voltage, be sure to replace an old one with an exact duplicate. If your wiring is aluminum, your receptacle must be designed to be used with aluminum wire (look for the letters CO/ALR.) use the terminal screws only, backwiring is not suitable for aluminum wires.

Replacing Appliance Receptacles

Appliance receptacles, rated from 15 to 50 amps, 240 volts and from 20 to 50 amps, 120/240 bolts, each require a special plug that will fit only that receptacle. Take care when replacing appliance receptacles because they have two hot wires, usually red and black, going to them. They may or may not have a separate grounding wire.

CAUTION: before beginning any work, turn off the power to the circuit. For a 240-volt circuit, you may have to remove two fuses or trip a two-handed circuit breaker.

Replacing a Grounded Receptacle

  • Shut off power to the circuit, unscrew the cover plate and remove.
  • Unscrew the receptacle from its box and carefully pull it out.
  • Note which wire is connected to which terminal screw.
  • Disconnect the wires from the screws.
  • To install the new receptacle, wrap the wires clockwise around the screws (use old receptacle as a guide.)
  • Screw the receptacle to the box and replace the cover plate.

Replacing a Backwired Receptacle

  • Shut off the power.
  • Push a small-bladed screwdriver into the slots next to the wires.
  • Pull them out.
  • To install the new receptacle push the end of the stripped black wire into the hole by the brass screws, white wire by the silver ones.

Replacing a 120/240-volt Receptacle

  • Shut off the power and remove the receptacle from its box.
  • Label the wires and screws.
  • Detach the wires.
  • Reconnect the wires to their proper screws on the new receptacle.
  • Reattach the receptacle to the box and replace the cover plate.

Professional Hint: Using Wire Nuts

For most simple repairs, you won't need to splice wires. But you may have to splice two or more copper wires to replace a damaged wall or ceiling light fixture or to make a connection in a receptacle, switch or junction box. To splice wires:

  • Strip 1 inch of insulation off the wires together clockwise.
  • Snip off 1/2 to 3/4 inch of the ends.
  • Cap the twisted wires with a wire nut, turning it clockwise to secure the connection.
  • Make sure the wire nut is the proper size for the wires.
  • CAUTION: Don't use any wire nuts to splice together a damaged extension cord. For safety, building codes allow you to splice house wires only within junction, receptacle, fixture or switch boxes. Also, be sure to turn off the power to the circuit before you make any splice.


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