[ramatsu]

This question is, I think, different from the others I found here about "using bare ground wire for neutral." In those, I think people were asking about sharing the ground and neutral function on the same wire.

My situation is: I to add a second light to a light that is on a three-way switch. (The two lights are to go on or off together at all times.) Due to circumstances that are long, elaborate, and I think unrelated to the real question, I find myself with an option for a properly routed hot wire, but without a corresponding neutral one.

There is however, a physical piece of romex that runs between them, for which I could fully disconnect the ground wire and have it dedicated to just the run between the two lights. (I have a solid ground opportunity for the new light separately). Then I could theoretically utilize that isolated length of ground wire inside the romex sheeting for my neutral.

I would tape the bare ground as it emerged from the romex sheathing at each end carefully with white tape and label it as neutral. Electrically, the circuit design would be completely proper. The only difference in the physical connections in the circuit would be that the new neutral wire wouldn't have its own sheathing inside the romex as the black, white, and red wires do.

The concerns I would have, and the best mitigations I could propose, are:
1) Issue: If there were sufficient load on that leg of the circuit, the bare-wire-inside-romex neutral might create heat issues that a true neutral, with it's own white sheathing, wouldn't have. Mitigation: The installation calls for just the single 75-watt lighting fixture to utilize this neutral, which might not be a worry, though I'd check into that too.
2) Issue: Future owners or electricians might be mislead or confused by nonstandard use of the ground wire. Mitigation: I would include folded documentation of the wiring kluge in the light fixture for future owners who might get the idea they want to add a row of halogen track lights at that end of the circuit.

With all that said, clearly the right thing to do is to rip out some sheetrock and run a new proper wire. But if the lack of insulation inside the romex isn't an issue for a neutral, I'd still consider the kluge.

But I'm looking for experienced eyes to say "Yeah, you should do it right, but theoretically there's no reason not to do what you propose" vs. "No, it flat out won't work or is dangerous for _____ reason that you haven't thought of."

Thoughts? Thanks, Allen

[hkstroud]

No, code violation and dangerous. Please post what you are trying to do in detail. If you have a 2-wire with ground cable between flight fixtures you only need to wire it properly.

[ramatsu]

@hkstroud: I've decided to tear it out and run the missing romex. But out of curiosity, which do you think would have presented the danger, heat issues with the ground wire inside the romex when used as neutral, confusing future electricians, or something else?

[hkstroud]

As stated the ground wire is not a conductor. By code it can not be used as a conductor. The sheathing of Romex cable is not considered insulation so you would have an uninsulated conductor if you used it a neutral conductor.

Could you provide the specifics of what you are doing. All you need between two lights fixtures that are controlled by the same switch is a 2-wire with ground cable.

If you are replacing an existing 2-wire cable between the fixtures, what are you replacing it with.

[ramatsu]

"The sheathing of Romex cable is not considered insulation"

... That pretty much would do it. As I said, I've decided to do it right and just tear out some sheetrock to run a new piece of 14-2. Wasn't replacing anything, just had a miswired new light that got covered by sheetrock and mudded before being fully checked out, due to rushed lack of communication between a couple of handymen.

Figured I'd end up going this way, as I'm not the guy who wants his insurance company to deny a claim based on a code violation whether it was the cause of an issue or not. But if a whole bunch of more experienced people had chimed in with "no worries," I would have considered it.

Thanks!

[hkstroud]

Good decision. I wouldn't be worried about the insurance company, I'd be worried about the incident that cause me to call the insurance company.