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I went to replace a GE 15086 Timer switch with a Leviton DH15S. The box it's going into contains 2 of the 15086 switches and one mechanical single pole switch. When I opened it up, I saw only black (hot), red (load), and green (ground) wires coming into the box (pic below). I've seen that described on this site as an "old style switch loop configuration". However, the old GE switches had their white and green leads both connected to the incoming green wire. I believe this is not correct (though it's unclear to me how unsafe it was).

After some further searching, I found a second junction box (pic below) feeding the one holding the switches (the wires go through the rear of this second box to the switch box described above). In this second box, the white (neutral) is clearly not going to the box holding the switches.

Based on this question I believe I need a neutral to power this switch. Can I tie in a new wire to the neutral wire nut in the second box and run it to the switch box to power the Leviton?

Thanks!

UPDATE I've dug around a bit more since my initial post and found more wrong (of course -- this was supposed to be a simple switch swap!). I've added a new image showing that THHN wire was run outside of conduit (and underscores Harper's observation below that the wrong box was picked by the original installer).

So in addition to running a neutral wire I'm now trying to figure out how to best address the unprotected wires here. Maybe flexible conduit from the exterior box all the way up to a new conduit-friendly switch box?

Switch Box Feeder Box Bare THHN

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  • What do the switch's instructions say? They are important and you need to follow them, NEC 110.3. Oct 1 at 0:23
  • It specifies to connect the white to neutral so I definitely need a neutral wire. Just curious if running a wire from the box outside is correct (that neutral runs alongside the hot that goes to the switch box)
    – nall
    Oct 1 at 0:38
  • @nall -- what wiring method was used to connect the inside-box to the outside-box? Oct 1 at 0:59
  • Connecting the Neutral to Ground (white to green) as shown in your first picture is a Very Bad Thing™ and a code violation.
    – FreeMan
    Oct 1 at 14:23
  • @ThreePhaseEel I've updated the post with a new image -- it seems whoever did this just ran bare THHN from the exterior box up to the switch, sigh.
    – nall
    Oct 1 at 15:02
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This setup uses THHN individual wires (note the writing on the wires) and part of this work is in conduit.

Now if all the work was in conduit, the answer would be as simple as pull a neutral wire from the same place that one of the hot wires comes from.

However, it is obvious that the 3-gang box was installed improperly. It appears the installer was unfamiliar with conduit wiring methods, grabbed inappropriate boxes intended only for use with the NM (Romex) wiring method. These things do not work together, so they decided to "just freestyle it".

Well, that doesn't work at all.

You have 2 choices: #1 you can remove and discard the box, and obtain a box actually made for use with conduit. Then connect conduit on the route to that other box (which I assume is on the other side of the wall?) and put all the wires in it, including your planned neutral.

Or #2 if cable is allowed in your jurisdiction, you can remove the box and remove all the THHN wire, and obtain "/3" NM cable and appropriate strain reliefs to bring the NM cable into the conduit wiring method, and reinstall that box using NM cable.

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  • Thank you, Harper -- this makes sense. Unfortunately, I've found new information (updated my post). If I go with your first option (replacing the box), can I run flexible conduit from the exterior box to turn that corner shown in my latest image? Or is there a better approach entirely?
    – nall
    Oct 1 at 15:05
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    @nall -- a 1/2" ENT (smurf tube) is a good solution, although you may want to swap out the inside box if you aren't comfortable putting a 7/8" actual diameter hole in its bottom to accept the conduit fitting Oct 2 at 0:40
  • @ThreePhaseEel thanks -- didn't even realize ENT was an option. Last question -- do all wiring methods going vertically in a bay need to be fastened to a stud?
    – nall
    Oct 2 at 2:41
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    @nall -- you'll need to fasten it to a stud somewhere within 3' of the box, but you shouldn't need much if any more securement for the raceway (ENT require securement every 3') Oct 2 at 2:43

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