How to Connect a Two Way Light Switch

Written by clare jackson
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How to Connect a Two Way Light Switch
Two switches in different locations can be very useful. (Jupiterimages/ Images)

Sometimes two-way light switches are not just convenient, they're a must. Imagine switching on the light at the bottom of the stairs and having no way to turn it off at the top of the stairs. Two-way light switches in the bedroom also can make pitch-black fumbling toward the bed a thing of the past if you install an additional switch next to your headboard.

Skill level:
Moderately Challenging

Things you need

  • Two-way switches
  • Electrical wire
  • Cable cutter
  • Cable stripper
  • Electrical connection boxes

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  1. 1

    Buy two specifically designed two-way switches from a hardware store. You will recognise these because they have three terminals on the back, while common switches have two. The terminals will be labelled "Com" for common, "L1" for Live 1 and "L2" for Live 2.

  2. 2

    Buy an appropriate length of wiring cable to run between the two switches. The wire should contain four elements; three sheathed core cables and a bare copper ground wire.

  3. 3

    Buy an appropriate length of 14-gauge house wiring cable that contains two sheathed wires and one bare copper ground wire. This will connect a switch to the breaker box.

  4. 4

    Replace the old switches with the new two-way switches; prepare the walls for any additional switches.

  5. 5

    Prepare the path where new cables will run. There will be new cables running between the two switches, and one running from the second switch to the light fixture. Dig a channel to set the cable back into the wall if necessary.

    Connect Power and Light

  1. 1

    Switch off the power at the breaker box.

  2. 2

    If there is not already power to either light switch then run two-wire house wiring cable between either switch and the breaker box. This cable will be referred to as "cable 1" and the switch as "switch 1".

  3. 3

    Connect the black wire from cable 1 to the "Com" terminal at the top of the first switch.

  4. 4

    If a light fixture is not fitted you will need to connect one. Use two-wire cable with black and white wires. Connect the white neutral wire from the light cable to the white neutral wire from cable 1 using a cable nut.

    Connect the Switches

  1. 1

    Run cable containing three wires (plus a ground wire) between your two switches. You'll see this cable has white, black, red and copper parts. This cable is now known as "Cable 2".

  2. 2

    Connect the black wire of cable 2 to the "L1" terminal at the bottom left of the both switches.

  3. 3

    Connect the red wire of cable 2 to the "L2" terminals of both switches. Both red and black wires indicate live terminals used in the transfer of power.

  4. 4

    Connect the light fitting to switch 2 via the upper "Com" terminal, using the black wire from the light cable.

  5. 5

    Connect the earth wires into the ground terminals, switch on the power and test to see if everything works correctly.

Tips and warnings

  • Be sure to buy a little more wire than you need for trimming purposes and to accommodate measurement errors.
  • Some areas might require electrical work to be performed only by licensed electricians. Check local requirements.
  • Always make sure that the wires you are working with are not live.
  • Keep water away from all electrical connections and make sure the surfaces are dry.

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