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3-Way Switch Wiring - Power Source at Fixture

By Donald Kerr
3-Way Switch Wiring - Power Source at Fixture

The following article explains how to perform three-way switch wiring when the power source is at the fixture.

Please Note

  • The correct wire MUST be connected to the common screw of a 3-way switch otherwise the switches will not control the light fixtures correctly!
  • The common screw may be located in a different spot on your 3-way switch than the location indicated in the drawings above, but make sure that the wire indicated in the drawings to be connected to the common screw is connected to the common screw of the switch.
  • The Common Screw of a 3-Way Switch is the Odd Color Screw (distinctly different in color from the other 2 main connection screws).

At the ceiling box--the ungrounded conductor (a.k.a. hot) from the fixture connects to the black wire from the switch. The white wire from the circuit power supply cable is the grounded leg conductor (a.k.a. neutral) for the fixture. The white wire from the switch connects to the black wire from the circuit power supply cable.


Legend: 1 - Circuit Power Supply Cable, 2 - Electrical Box where the light fixture is mounted
3 & 4 - These wires MUST be connected to the common screw, 5 - Light fixture

Proper Steps
Wrap a piece of black electrical tape around both ends of the white wire going between the switch and the fixture to indicate that the wire is being used as a ungrounded conductor (a.k.a. hot). Also do the same to the white wire going between switch box 1 and 2, as this wire is also being used as a ungrounded conductor (a.k.a. hot).

Bare wires (not shown in the diagrams) are together and grounded to box (if metallic) and if the fixture has a green wire or a grounding screw, it gets grounded also. Bares and green wires are equipment grounding conductors.

If You Need Onward Power From the Fixture Then:

If Only Switched Power Required Onward Then at Existing Fixture:

  • Onward cable--black/white/bare
  • Connect black from onward cable to the black coming from switch
  • Connect white from onward cable to white wire of the circuit power supply cable
  • Connect bare from onward cable to bare coming from circuit power supply cable and to electrical box if metallic
  • At the onward cables destination, the black is the switched ungrounded conductor (a.k.a. hot), the white is the grounded leg (a.k.a. neutral), and the bare is the equipment grounding conductor

If Only Unswitched Power Required Onward Then at Existing Fixture:

  • Onward cable--black/white/bare
  • Connect black from onward cable to black wire coming from circuit power source cable
  • Connect white from onward cable to white coming from circuit power supply cable
  • Connect bare from onward cable to bare coming from circuit power source cable and to electrical box if metallic
  • At the onward cables destination, the black is the ungrounded conductor (a.k.a. hot), the white is the grounded leg (a.k.a. neutral), and the bare is the equipment grounding conductor

If Switched and Unswitched Power Required Onward Then at Existing Fixture:

  • Onward cable--black/red/white/bare
  • Connect black from onward cable to black wire coming from circuit power supply cable
  • Connect red from onward cable to the black wire coming from switch
  • Connect white from onward cable to white coming from circuit power supply cable
  • Connect bare from onward cable to bare coming from circuit power supply cable and to electrical box if metallic
  • At the onward cables destination, the black is the unswitched ungrounded conductor (a.k.a. hot), red is the switched ungrounded conductor (a.k.a. hot), the white is the grounded leg (a.k.a. neutral), and the bare is the equipment grounding conductor

If You Need Onward Power From the Switch Then:
This is not possible with this configuration as no grounded leg (a.k.a. neutral) exists at the switch locations.

If wiring multiple fixtures be sure to check the following guidelines concerning how to do it and what not to do: Wiring Multiple Fixtures.

If you are new at understanding the "politically correct" electrical terminology and need clarification of the terms used, we strongly urge you to read the Clarification of Definitions and Terminology guide. This will explain the terminology used in this article.

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