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Based on the answer to my recent question "How to wire a 240V disconnect panel for spa that does not require neutral", I need to run another wire from my main service panel to my spa disconnect panel to serve as neutral.

Current Situation

I began wiring already and noticed my problem halfway. Oops.

  • I have three 6 AWG wires running from my main panel to my 60A spa disconnect panel:
    • hot red
    • hot black
    • grounding green
  • All are THHN/THWN-2 rated
  • In locations where conduit is required, I'm using 3/4" liquidtight flexible nonmetallic type-B

Proposed Fix

Re-purpose the grounding wire and make it my neutral instead. I would then need to run an additional wire for ground.

My goal is to run the new grounding wire in the same 3/4" conduit I already have if possible. After reading NEC table 250.122, the grounding wire requirement for a 60A panel is 10 AWG copper.

I would put white tape (and a note) around the re-purposed green wire to prevent future confusion.

Questions

  1. Can the grounding wire be bare if it's in conduit, or does it also require THHN/THWN-2? There are wet locations along the run.
  2. Can I run the new 10 AWG grounding wire in my 3/4" conduit which already has three 6 AWG wires?
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  • Could you put the GFCI breaker in the main panel, then use a regular breaker in the disconnect? – Tester101 Oct 5 '15 at 2:11
  • My main panel is quite far from the disconnect panel - roughly 60ft. Would this distance defeat the purpose of the GFCI breaker? – Scott Lin Oct 5 '15 at 3:09
  • I wouldn't think 60 ft. would make a difference, but I could be wrong. – Tester101 Oct 5 '15 at 3:15
  • According to documentation for QO® and QOB Miniature Circuit Breakers, Qwik-Gard GFCIs "must be located no more than 250 ft. (76 m) from the load being served.". Check the documentation for the device you're using, to determine if the GFCI can be installed in the main panel. – Tester101 Oct 5 '15 at 11:07
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You CANNOT re-purpose a green wire smaller than #4 as a neutral, even if it is insulated. Is the #6 ground green all the way? If so running a new neutral in this case is your only option.

The ground wire in the outside portion of the wiring for a hot tub in conduit CANNOT be bare. It MUST be green insulated.

I would use a GFI in the main panel and a regular breaker in the spa disconnect. Easy-peasy.

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  • I can't re-purpose the wire even if the neutral isn't going to carry any current except when the GFCI test button is pushed? When pushed the current should be minimal, right? My assumption with this system is that the hot red and black wires will be carrying the load. See my linked question, which is also linked above. – Scott Lin Oct 5 '15 at 2:54
  • Not if you want the installation to be code complaint. And why are there two questions if you keep linking back to the other one? – Speedy Petey Oct 5 '15 at 2:55
  • Because I felt this question would pollute the other answer. Thanks for your answer. I want to be code compliant. Do you know which NEC section relates to your answer with respect to the neutral wire size? – Scott Lin Oct 5 '15 at 3:07
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    My suggestion is to rip out your installation and do it right. Stop trying to jury rig a non-compliant installation to cover up a mistake. – Michael Karas♦ Oct 5 '15 at 9:16
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    It's not a matter of the size, it's a matter of the color. – Speedy Petey Oct 5 '15 at 11:03

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