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I'm trying to install 2 smart wifi switches to replace 2 dumb switches in a box. 1 switch powers a dining room light. The other switch powers two kitchen lights that turn on/off together. As expected, I found 3 wire bundles entering the box (with 2 wires in each sheath, one black and one white). One of the black wires is hot (connected to a red nut). 2 of the black wires are loads going to the lights. All of these wires are on the same circuit because they are run through the same breaker.

This all makes sense to me. However, I expected the 3 white (presumably neutral) wires to be connected in a bundle. I would then tap that bundle for the smart switches, but they are individually capped. They also have a small amount of voltage in them when I tested them with a voltmeter. But all the lights and switches work with the dumb switches, so there doesn't seem to be a problem.

My question is: should I bundle the 3 white wires together? Was that just an oversight when they were being installed? And then can I tap that bundle for smart switches? How can I be sure the 3 white wires are the right neutrals?

You can see three sets of black and white wires entering the box, and 3 capped white wires

https://www.amazon.com/gp/product/B07Q8FRJ96/ref=ox_sc_saved_title_1?smid=A3KD59IVUZ5TBM&psc=1

Here is the smart switch I would like to install. I don't have the manual yet because I don't want to buy it until I'm sure it will work.

I confirmed that this box is not grounded and does not have a ground wire.

And updating with pictures of two of the three lights. The third is hard to disassemble, but its wiring runs with one of the two pictured. These all look standard to me. Black with black, white with white, and grounded to the box. All lights work. Note that although the wiring in the box look new, these wires likely were originally installed many decades ago. The house was built in the 1920s but has been updated over time, so the wiring could be quite old.

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  • Can you open up one of the lights and see what's going on there? The light should use the hot and neutral from the same cable, but they might be using a neutral from somewhere else. Perhaps this was part of a small remodel where the switched wires were re-ran so now it's a little non-standard.
    – JPhi1618
    Sep 24, 2019 at 17:50
  • Yes I can open up the lights easily, but what are the steps I would do to check that they are the right cables? Thanks!
    – Bob Sacamano
    Sep 24, 2019 at 17:57
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    Yeah, there's a big problem with this setup here if the lights worked before. I'm also concerned about why there are no ground wires in what looks like recent work. The only thing I can imagine is the cable is AC (which grounds via the sheath/clamp) and they're wrongly using ground as neutral. Look, I realize you just want the shortest path to "my lights work", but this is so dangerous that you cannot turn your back on it. We gotta know what's happening with neutral up at the lights, and from there, we can advise.
    – Harper - Reinstate Monica
    Sep 24, 2019 at 18:07
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    Ok appreciate the responses. I will figure out where those neutrals are going (hopefully) when I go home tonight and report back.
    – Bob Sacamano
    Sep 24, 2019 at 18:12
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    PLease define "smart switch" and preferably post the model so we can look at the installation manual.
    – Carl Witthoft
    Sep 24, 2019 at 18:12

4 Answers 4

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Some locations (switches) may have a neutral, others may not. Depends on the previous electrical installations, electrician/installator...with smart switches is exactly the same, depends on the model of the smart switch. Some need that neutral wire, others not. But the vast majority of smart switches require that neutral wire. I'd connect the dining room neutral wire to the smart switch (let's just say A) and then other 2 together under one cap plus a white wire which goes to the other smart switch B. Remember all the neutral wires that are connected should belong to a single circuit.

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Watch Out for Unlisted Switches

The linked switch is advertised as:

CE, FCC, ROHS, CQC Certified

  • CE - Means nothing (Harper has his own creative definition)
  • FCC - Related to radio frequency interference but tells you nothing about electrical safety
  • ROHS - No hazardous substances (e.g., mercury, lead, etc.) but tells you nothing about electrical safety
  • CQC - Not sure what this one is. But probably nothing to do with electrical safety

What you generally want to see is UL Listed. Possibly ETL or something else as an alternative.

This doesn't matter as much for plug-in devices - you can unplug them if they start smoking. But for something permanently installed, it is a big deal.

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    CSA is another "real" marking, though it only has legal standing in Canada, presumably. But it is a real standard.
    – Ecnerwal
    Sep 25, 2019 at 2:06
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This is not a legal installation. A current carrying wire must be bundled with the return path. That is if you map out the path that the current takes then the area inside the circuit must be as small as possible. Otherwise there will be a magnetic field generated by the loop.

To fix this situation you would need to find where those 3 romex cables end up and route the neutral through the switch box properly.

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These neutral wires should be bundled together (assuming they are neutrals - this is weird enough that we shouldn't assume anything though)

Since the wire doesn't even seem to have a ground (I really hope they didn't clip them off at the edge of the sheathing - I had a couple outlet boxes where that was done in my house and wound up having to fish new Romex just to properly replace standard grounded outlets), I'm not sure how they could have gotten the lights to even function without them (and if the lights are using ground as a neutral, this is wrong and needs to be corrected). Definitely looks like 14/2 Romex coming into the box, not BX. There must be another neutral in the lights' boxes that they're using instead, but it's better to use the appropriate neutral instead.

Also note that NEC requires all metal boxes to be grounded if a ground wire passes through them. If there's truly no ground wire, you should use non-conductive (ie plastic) screws to fasten the switch plate to prevent shocks.

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    We don't yet know that they ARE neutrals. Being a white wire does not always mean that, especially when there is evidence of odd work. While a white used for another purpose should be remarked, they often are not. What they are (or are not) connected to at the other end matters a great deal.
    – Ecnerwal
    Sep 25, 2019 at 2:04
  • You're correct, we can't be certain yet that they are neutrals. I might be jumping the gun on that advice.
    – Nate
    Sep 25, 2019 at 2:21

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