Continuing my basement shop brainstorming...

As I said in another question, the good news is that I've got a 30-amp 240V circuit more or less in the right place and available, and easily accessible for its entire length.

The questionable news is that it's a 3-wire circuit -- no safety ground. It's in conduit, but I never like trusting the continuity thereof.

So: How insane would it be to run a new safety ground outside the existing conduit?

... Or should I just scrap the old run and redo it as NMC/Romex?

... Or should I put a GFCI in the new secondary box on principle (probably!), in which case safety ground is mostly moot? I've used that solution for several outlets that had the same problem..

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    Seems worth it to just replace the whole thing with a #6/3 w/ ground instead just going through all that trouble for one conductor – Kris Sep 2 '15 at 1:06
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    @Kris Sure, if money is no object. – Tester101 Sep 2 '15 at 1:33
  • How long is the run? – Tester101 Sep 2 '15 at 1:34
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    What kind of conduit is the existing wire in? Do wire fill rules prohibit you from pulling a ground wire inside the conduit? – Craig Sep 2 '15 at 7:50
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    Yeah, what kind of conduit is the existing wire in? Rigid and EMT behave very differently as a ground conductor. – ThreePhaseEel Sep 2 '15 at 11:43

Pull out the wire that's in conduit, (look it over, but it's probably just fine) pull in that wire and a ground.

It's darn near impossible to pull in another wire without pulling the whole bundle out and back in. It's fairly straightforward to pull the whole bundle out, add a wire and pull back in, unless the conduit is too small.

Code-wise, (250.118) properly installed metallic conduit (RMC, IMC or EMT) is a ground, whether or not you personally like it. It's not copper, but it's got a large cross-sectional area and the fittings are designed to maintain contact if properly installed.

I would not consider Romex an upgrade. I've seen too much rodent/Romex interaction to love it much, and with the possible exception of wire old enough to use cloth-based insulation as primary there's little benefit to "new wire" over "old wire."

  • Hmmm. If code accepts it... I need to sanity-check that nobody ha/s done something rude to it, but maybe I should just decide I'm being paranoid? – keshlam Sep 2 '15 at 14:40

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