I am having trouble identifying which wires are in my box despite all the colors being quite clear.

The voltage drop between: White-Ground= 123.5 Red-Ground= .3 Black-Ground= .3 Black-Red= 0 Black-White= 123.3 White-Red= 123.5

I would think if the white is actually the neutral wire, but then the voltage between the white and ground should be very small. Is the white here the Load?

Related to this question, using this this picture:enter image description here

  • 2
    Is there another switch in this circuit? Commented Mar 29, 2018 at 11:37
  • @ThreePhaseEel, Yes, it's a three way light.
    – wizlog
    Commented Apr 3, 2018 at 19:37

1 Answer 1


What you have is a switch leg. In the past it was a best practice to wire the white hot so it was not confused as a neutral the white was supposed to be marked with a different color than white or green with tape or paint marker, but that step was not always done in the past by pro's and rarely by DIY folks, I usually carried a black marker and marked them but not always to tell the truth. With white being hot the power is being fed from the fixture on the white to the switch and then with the switch in the on position you will find it is also hot allowing the power to flow to the fixture.

  • Why are there three black leads coming out of the device at bottom (a switch? what kind?)? I would have thought there would be a black, a white, and a red (or a green if a ground). Are these leads supplied as part of the device or did an installer add them? Commented Mar 29, 2018 at 11:26
  • 1
    @Jim Stewart the photo was an example not the op's, but I am sure if the photo is high enough resolution you could read the type of switch connections From the tags ,possibly a 3 way? Or that would be my guess.
    – Ed Beal
    Commented Mar 29, 2018 at 11:34
  • @JimStewart the timer was connected with three blacks, not sure why.
    – wizlog
    Commented Apr 3, 2018 at 19:34
  • @EdBeal Yes, this is a three-way. Thanks for the answer! Just curious, why wouldn't they just wire the white as neutral and keep power on the red and black? Also, when did best practice change?
    – wizlog
    Commented Apr 3, 2018 at 19:36
  • @wizlog -- they needed red & black for travelers, so the only usable wire left for the common wire was white, leaving no space for a neutral as a result. This was fine when the most sophisticated thing in a wallbox was a wind-up timer or triac dimmer, but isn't so hot for smart-switches that need power themselves to run. Commented Apr 3, 2018 at 22:43

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