Hello I am trying to install a WiFi light switch that requires a neutral line. I could look at the Lutron but I figured I would ask about this possible solution as I have these switches elsewhere. I have read many threads and I think I can resolve this on my own. I’m fairly competent but certainly not a professional.

From my front door I control the driveway light pole. There is a junction box in the garage that the light pole comes into. From what I can tell the junction box is also tied into by the garage interior and exterior lights. There is a large bundled group of neutral lines in this junction box as well.

My problem is that the from the junction box to the switch they ran a line and with no neutral. I don’t know if there was a specific reason. So my question is can I replace this line from the junction box to the switch with a new one with a neutral line? And can I connect the new line to the bundle of neutrals in the junction box? I have read that it’s better to go back to the panel but I think I am good to connect to neutrals in the junction box in the garage?

Again, I am fairly competent but also know that something like this can be a borderline call an electrician task.

Thanks, JDW

  • Can you mount a "master" switch at the junction box in the garage? – ThreePhaseEel Jan 13 at 4:53
  • Are you able to replace the electrical cable between the junction box and switch? – Harper - Reinstate Monica Jan 13 at 8:39
  • @harper I can easily access and replace the wire. – JDW9820 Jan 13 at 14:20
  • @Three I can as far as I can see the power coming into the junction box has it’s own circuit. – JDW9820 Jan 13 at 14:20
  • Just FYI I don't endorse buying from Home Depot, but if you do, they have really weird/broken prices on /3 NM cable right now. Cross-check prices with /3 UF cable, which is more robust and should be more expensive, but sometimes is not. – Harper - Reinstate Monica Jan 13 at 17:34

Option 1: Steam or smart switches, cable change

Replace the cable run between garage junction box and switch. To wire this old school, you need three active wires in the cable:

  • neutral (neutral must be white, white isn't necessarily neutral)
  • always-hot, so the switch has something to switch, preferably black
  • switched-hot, the output of switch, ideally red

And voila, /3 cable contains those exact colors.

When buying cable, look at the breaker on that circuit. 15A breaker: 14AWG is acceptable. 20A breaker: must use 12AWG.

Option 2: Certain specific smart switches, no cable change

In this scenario, you re-task the black and white wire to the switch to actually always-hot and neutral. Switched-hot is no longer in this cable.

At the switch, you install a smart-switch "remote" that is designed to communicate wirelessly or via power-line signaling. It needs only always-hot and neutral. In the garage junction box, you install a smart-switch "master" (or faceless module which does the same thing) and pair it to the remote. The master takes always-hot, neutral, and switches a switched-hot or load output.

Shopping assistance or product recommendations are off-topic here, so I cannot advise you on any particular models.

  • Well, option 1 involves a smart-switch, just at the location of the existing switch :) – ThreePhaseEel Jan 13 at 17:30
  • @ThreePhaseEel true, forgot why we were here :) – Harper - Reinstate Monica Jan 13 at 19:43

Power in to junction box:

If you have power going in to the junction box then they are using a 14/2 or 12/2 wire going from the junction to the switch box with one of the wires re-purposing the neutral as a switch-leg. In which case, both neutral and black are HOT. In this circumstance you should see a neutral marked as black in the switch box and junction box (not all electricians do this). If you have two blacks then your wire must have been run in conduit (super easy to add a neutral then).

enter image description here

Drawing is the wrong and now-illegal way to do it, but that's where you're at now.

In this scenario you can just abandon the current wires going to the switch and wing nut them off and mark them in the switch and junction box. Then put a new switch box next to the junction box using 14/3 between them. The wiring would be the same as in the diagram above however the white wire would be switched with a red wire (switch device would have 1 black and 1 red attached) and neutral would stay neutral in your new switch box.

OR do the same wiring scheme that I just mentioned but abandon the 14/2 (again) and run new 14/3 to the current switch box from the junction box.

OR if your wires are in conduit, fish a neutral to the junction box through it and you don't have to do any other work but connect it to the bundle in the junction.

Option b is that the power goes in to the light box, in which case you would have a neutral in there; but I take it that is obviously not the case.

If you have any question feel free to ask, but do include pictures of your junction and switch box wiring.

** Please note: if this is a 20 amp circuit (which I doubt) you would need 12 gauge wire. You can tell if it is by looking at your panel, the romex jacket, or just judging the thickness; 12 gauge wire is harder to bend.

  • The rest of my house has been very good about carrying neutral lines throughout. The light pole switch was clearly added on after the fact. I think it originated at the junction box but again was moved to the front door and only ran 12/2 line. I can easily access the line and replace with a 14/3 line. I guess I am over thinking as I don’t know why they didnt use a 14/3 line to the switch to begin with. I am worried about the tying in the neutral line to the wrong place. However if there is a line coming in to one junction then I should be good to use that neutral line? Thank you – JDW9820 Jan 13 at 14:35
  • I’ll try and grab pictures and get back to you all. Thanks again. – JDW9820 Jan 13 at 14:36
  • @JDW9820 that's typical. The Web is lousy with drawings exactly like the one linked in this answer, which is wrong and illegal. (The law changed in the 2011 NEC with years of notice that it would be changing; the people cranking out these drawings are just lazy and irresponsible.). So when a homeowner decides to add some wiring, and searches the webfor a wiring diagram, he gets misled. – Harper - Reinstate Monica Jan 13 at 17:32
  • @JDW9820 that's typical. The web is lousy with drawings such as the one linked in this answer, which is wrong and illegal. However when you search for a drawing that is correct, it's slim pickings, which is why it's hard to show you a correct drawing. Anyway, that may also explain why the last homeowner did it wrong, it's hard to find advice to do it right. – Harper - Reinstate Monica Jan 13 at 17:45
  • it is wrong according to current standards for exactly the reason why he needs the neutral (funny enough), but it is what he has @Harper (probably). 14/3 will make it code compliant. also JDW9820 please read what i wrote about wire gauges - if you have 12/2 currently you need 12 gauge on the rest of the circuit e.g. 12/3. – Alex Jan 14 at 7:45

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