How to Wire a 3 Terminal Rocker Switch

Written by charles w. st.clair
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How to Wire a 3 Terminal Rocker Switch
(Comstock/Comstock/Getty Images)

Three-terminal rocker switches are also known as three-way switches in the U.S. This is a curious misnomer, since so-called three-way switches allow a person to control a device, usually a light, from only two separate locations. Wiring a three-terminal switch is fairly straightforward, provided you have kept your wires organised.

Skill level:
Moderate

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Things you need

  • Wire cutters
  • Wire strippers
  • Phillips screwdriver
  • Voltage tester
  • Wire connectors

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Instructions

  1. 1

    Disconnect or shut down power from the source. Use your voltage tester to make sure that there is no power being supplied to the wires on which you will be working. Shocks from voltage can cause injury or death.

  2. 2

    In order to install a three-way switch, you will have to have two separate power cables present. One will be a two-wire cable with both a black and white wire present, as well as a ground wire. The second cable will be a three-wire with a black, white, and red wire plus the ground.

  3. 3

    Strip the outer sheath from each of the cables, and then strip about 1/4-inch of the insulation from the end of each wire in the box.

  4. 4

    Attach the black wire from the incoming power to the common screw terminal, which is usually coloured black, by making a small hook. Slip the hook over the screw and tighten the screw with a Phillips screwdriver.

  5. 5

    Attach the black wire from the three-wire cable to one of the bottom terminals, known as travellers. These screws are usually coloured silver. Attach the red wire to the other traveller terminal. Use the same method described in Step 4 to attach the wires to the terminals.

  6. 6

    Join the white wires together with a wire connector. Join the ground wires together with a grounding pigtail using a wire connector. A pigtail is simply a short, 2 1/2-inch section of wire with both ends stripped back a little bit. Connect one end of the pigtail together with the two ground wires and the other end to the grounding terminal on the switch. The switch ground terminal is usually located in the bottom right-hand corner of the switch on a small tab.

  7. 7

    The other light switch should be wired exactly the same way, with special attention paid to the placement of the three-wire black and red wires. If these wires are reversed, neither switch will work properly. Push the switch back into the box, and attach the switch to the box using screws.

Tips and warnings

  • Keep track of your cables during installation by labelling the ends when the cables are being pulled. This technique helps eliminate frustration and confusion when it is time to install switches and devices.
  • Always turn off power at the source before working on electrical wires. Use a voltage tester to confirm that the correct steps have been taken to ensure safety.

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