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I have a two-switch junction box where the switch on the left is a 6-way switch and the switch on the right is a 3-way. I'd like to swap the 3-way switch out for a Lutron smart switch and require a neutral for that change.

Even though this is new construction ~2021, I don't see a white wire bundle in this box which I thought was code. However, I do see a capped purple bundle that isn't connected to either of the two existing switches. Can these wires be safely considered the neutrals in this case?

Update with more details: In the interest of trying to be to the point with my question, I tried to frame this question as simply as possible. However, some additional context:

  • the other end of this 3-way switch is a dead-end 3-way switch with two blacks and one red wire.
  • the intent of replacing the 3-way in the photo above is to replace the dead-end 3-way with an always hot receptacle (I'd be using Lutron's Caseta 3-way switch here + battery pico at the far end for this purpose).

Based on the above, my goal was to find a neutral in this box for the new switch and then repurpose one of the travelers as a neutral for the receptacle at the far end.

Switch box wiring

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  • In the EU maybe, NA neutral colours are mainly white, sometimes grey. Any other colours should be consider hot, except green. Assuming is usually bad with electricity
    – crip659
    Commented Apr 24, 2022 at 15:36
  • Can you post photos showing the other entrances into the box please? Commented Apr 24, 2022 at 15:52
  • why don't you say anything about the purple wires? ... after all, you are asking if they can be used as neutrals
    – jsotola
    Commented Apr 24, 2022 at 17:22

2 Answers 2

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As I understand it, neutral is required to be available or able to be easily added later. Effectively that means that with cables you must have neutral as part of the initial installation but with individual wires in conduit you can add neutral later when you need it. You have colors besides black, red and white, so you have conduit. (There are other clues, but the colors are definitive.) If you don't have neutral, you can add a white or gray wire for neutral in the same conduit as the hot/switched hot/traveler wires.

Three other things to note:

  • As far as I know, you can never repurpose a non-white/gray (e.g., black, red, purple, yellow, orange, etc.) wire as a neutral wire. There are certain cases with cables where you can, due to the nature of cables, use a white wire as something other than neutral (e.g., black/white for a 240V-only circuit). So marking a purple wire as white to use as neutral is not an option.

  • Neutral "everywhere" is not necessarily the case for a 3-way switch. It may be (can't say for sure) that you are only required to have neutral available/able to be added at one of the switches. And even if the requirement is everywhere, to save money when using conduit the builder may have only pulled a white/neutral to the first switch, knowing that it could be added to others later.

  • Depending on the wiring configuration and the particular smart switch, you may only be able (neutral permitting, of course) install this smart switch to replace the first switch in sequence (panel->1->2->lights) and not the second switch. The smart switch instructions should provide more details.

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  • Thanks for your insight. I think it's clear from the responses so far that assuming anything with a different color is bad practice. I will add that the far end of the switch is a dead-end three way (at the bottom of a stairwell at my egress door) and only contains 2 blacks and 1 red all connected to the switch. I've added some more context on the basis of my question to the original post in an update. Commented Apr 24, 2022 at 16:16
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    The beauty of conduit is that for things like this you just add more wires. In fact, you might be able to add wires for a receptacle without changing your 3-way switches at all. It isn't trivial, but it is a lot easier than running new cable through a finished space Commented Apr 24, 2022 at 17:02
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You are in metal conduit, that is where I live. All of the research you've been doing has presumed you are dealing with Romex cables that are unchangeable in the walls, you need to ignore those bits.

Even though this is new construction ~2021, I don't see a white wire bundle in this box which I thought was code.

In conduit, it's super easy to pull additional wires later, so the wire doesn't need to be installed if they leave room for it. Which they did.

However, I do see a capped purple bundle that isn't connected to either of the two existing switches. Can these wires be safely considered the neutrals in this case?

No chance of that. Purple is not a neutral color, it's another hot wire doing a task unrelated to your project.

I really can't see what's going on in this box because of a) all the white crud on the wires, and b) you didn't take a photo looking up into the pipes. If you cleaned off that white crud and took that photo I could tell you a lot more.

the other end of this 3-way switch is a dead-end 3-way switch with two blacks and one red wire.

Okay, that bodes well for your project. By the way, the building codes require you to have switches at certain entrances. Builders don't install lengthy conduit runs for their health, so most likely this switch is mandatory. No trouble though, you can eat your cake and have it too with a combo switch-receptacle. Or you could use a wireless remote with that smart switch you are adding.

Based on the above, my goal was to find a neutral in this box

See, that's you still thinking in Romex: "the wires in the walls can't be changed and I must FIND wires". No, in conduit, you put in the wires you want. It feels hard only because it's new.

By the way, in conduit there is no re-marking wires to change their function. You install the correct wires and that's it. Better hardware and lumber stores (i.e. not big-box) sell THHN by-the-foot, and if you need a color they don't have, 3M Super 33 electrical tape is sold in 10 colors anywhere for $4 (and mini 5-packs of popular colors for $6).

You generally want to use THHN solid wire, #12 is the universal donor but #14 is allowed if all the other wire is.

With metal boxes, you want to use the $3 spec grade outlets which do two nice things for you: #1 they self-ground via the mounting screws (due to a scraper brush on the screw), and #2 they use "screw-and-clamp" back-wiring which makes it possible for a novice to work with stranded wire. Your old wire might be stranded. Stranded is really better, but too difficult to put on a side screw and not legal in a backstab.

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  • Did you mean “you generally want to use THHN stranded wire” instead of solid? I switched to stranded because of you ya know… lol
    – aerospark
    Commented Apr 25, 2022 at 3:44
  • @aerospark LOL thanks, but I got sick of explaining to novices how to put stranded wire on a side screw. Commented Apr 25, 2022 at 3:46

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