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I'm trying to install a wemo dimmable smart switch to replace a regular switch. The original wiring pictured below is unlike the other 8 switches I replaced in my home. It looks like it's hooked up to two switches next to each other. One of the switches does nothing. The other controls the lights and dimms them.

When I remove the extra switch from the equation and just have the white wire and the red wire hooked up to a regular switch with the black wire unattached the switch still works like it should. This tells me that the white wire is live? I tested it with an mtool and it does buzz. When I insert the smart switch white to white, red to red, black to black and green to metal frame does nothing. However, I can rearrange the wires where regardless of if the switch thinks it's on or off the lights remain on. So the questions are:

  1. Is the black wire neutral? If not, what is it?
  2. Could the switch be defective or is this wiring conducive with an always on possibility?
  3. Is there a wiring configuration that would actually work?

original wiring

  • Is this a location where a 3-way switch would make sense? – Harper Oct 1 '17 at 16:13
  • No. These lights are in the living room and the switches are together. There's no other switches that control these lights (though maybe there was another switch somewhere before as the previous owners knocked down some walls and redid the layout of the rooms). – Irina M. Oct 3 '17 at 3:08
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If you have two switches and only 3 wires feeding them then here is what they most likely did.

When creating a switch leg for lighting or other loads using non-metallic cable, the National Electrical Code requires that the white wire be connected to the hot feed to the switch and re-identified some other color (except gray). Usually it is re-identified with tape as a black wire because that is what electricians carry with them.

In your situation, the white wire would then be the hot feed to the pair of switches. After the switches, the black would go to one load while the red goes to another. If this is for a ceiling fan then the black would feed the fan and the red to the lights or vice versa.

This means there is NO neutral present at this switch location regardless that the wire there is white. Someone just never re-identified the white wire as is required by the Code.

To use a smart switch at this location you will need a smart switch(es) that does not need a neutral wire. It would use the ground wire to stay active while it waits for motion or a wifi signal. Apparently, the smart switch that you have needs a neutral since it has a white wire. Look for switches marked "NO neutral needed".

Good luck and stay safe!

  • Thanks! I think you are right. It's weird though cause every other switch I replaced has had either a neutral or a bunch of neturals together and these are recessed lights with no fan (or even a possibility of a fan). Does that mean that at one there was a fan and when they put the recessed lights in they didn't rewire? Also, would that mean I can swap the black and the white at the lights somewhere and add neutral in there somewhere? – Irina M. Oct 3 '17 at 3:06
  • The other switch locations were probably where the feed for the circuit comes in. That is why there is a neutral there. When the main feed comes first to a light or fan box then a switch loop is created to control it that normally would only require two wires. The switch is inserted in series with the hot leg so you have a hot leg and a switched return leg with no neutral. The only way to now get a neutral to the switch location is to replace the cable to the switch location or add another cable. This would normally involve removing drywall or plaster and then repairing it. – ArchonOSX Oct 3 '17 at 9:54

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