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I think that my house has a three way switch wired like this diagram. I think it's this one because both switches only have one bundle with three conductors and a ground coming in. Would I be able to use a smart switch that requires a neutral wire with this setup?

wiring diagram

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  • Not all smart switches wire the same. If you want to know compatibility we would need model of switches you wish to use at each location.
    – NoSparksPlease
    Commented Jul 31, 2023 at 2:18
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    See the black mark near each white wire connection (except to the light fixture)? That's turning the white wire from the default neutral to a traveler. Meaning, if you have a configuration matching this diagram then you don't have neutral in the switch boxes. Except, you will open the boxes and find the white wires don't have the black mark - that's because it is often not done, but it is implied.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 31, 2023 at 2:27
  • Makes sense, it seems that the rehab was done on the cheap. Is there a way to convert one on the wires to a neutral?
    – Baasic
    Commented Jul 31, 2023 at 2:30
  • Not "one of", only white can be neutral. You need to look for smart switches that don't need two travelers.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 31, 2023 at 3:18
  • Why would you want to keep this setup if you are going to use smart switches? Just re-wire them so both switches get hot and neutral, then connect only one of them to the switching wire and put your first smart switch there. Then all options are open. You can leave the second box empty and have only one switch. You can replace the second one with a battery operated switch (no wires at all, just a radio connection to the controller). Or you can use a second smart switch that is connected to main but not to the light, again, just radio connection to controller.
    – Orbit
    Commented Jul 31, 2023 at 13:33

2 Answers 2

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Yes you can, it depends on what smart switch you get. This would work with what I have installed.

  • You have neutral and live coming in
  • You use white and black for that to both switches.
  • One smart switch would use the red to supply the bulb.
  • The smart second switch would talk to the first one.

Mine is a full fledged install with the server. But I could program two switches to link to each other directly and take the server away. It is what I am about to do with my holiday home, where the buyer does not want automation. I have remote switches already, so I am going to reprogram them to communicate directly and take the server away.

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    The second smart switch (remote) would need to talk to the first one via radio or powerline communication, though. The red wire is not available for that purpose since you're using it for switched-hot.
    – Harper - Reinstate Monica
    Commented Jul 31, 2023 at 7:15
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Probably not, or not easily.

Neutral isn't present at either of the switches; there is a hot and two traveller wires on one end, and two traveller wires and a switched hot on the other. that was unless out the vast majority of smart switches unless you are in a position to pull new wire. This is one of the problems with switch-loop wiring; unfortunately it was popular at one time.

There are a few that have run on 'parasitic power", trying to use a trickle current through the load to power themselves. That worked better with incandescent bulbs that it would with compact fluorescents or LEDs.

The best suggestion I have that doesn't involve new wire is an ugly one: rewire so the outlet is in switched but both switches get hot and neutral. Use that to install smart switches strictly as in-wall remotes; don't use their output terminal all. Install a smart bulb in the now-always-on socket, and program the smart home systems to switch the bulb on or off depending on the signals received from the switches.

(I may have to do something like this to control some of my own lights. Insert grumpy-old-man noises here.)

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  • Or better yet, use a system like Insteon that lets you put a switch module at the fixture
    – ThreePhaseEel
    Commented Jul 31, 2023 at 3:13
  • @ThreePhaseEel True. That's my current plan for the ceiling fans, since that also gets me independent control of light and fan. Need to decide whether I trust the modules I have on hand.
    – keshlam
    Commented Jul 31, 2023 at 3:56
  • Why use a smart bulb? The switches have 3 wires, if they get hot and neutral both still have a free wire to use as switched, you can use either.
    – Orbit
    Commented Jul 31, 2023 at 13:38
  • @Orbit: ... That's what I get for posting when tired. Yes, one can be a switch loop while the other is just a transmitter.
    – keshlam
    Commented Jul 31, 2023 at 14:51

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