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I have 2 dedicated circuits:

  • 40 amp water heater
  • 30 amp electric range

Both have 2 hots and a neutral grounded at the panel. One runs through a junction box where the wires are connected and continue to the water heater, the result of a previous revision. All wires are individually insulated and encased in EMT mounted to the overhead joists in the basement.

In order to add a ceiling, I replaced the "junction box to water heater" and "panel to range" runs with FMT in the joists with 8/2 and 10/2 NM-B. The white and black wires are used for the hot and the uninsulated ground for the neutral. I used extra insulation from the stripped wires to cover the exposed tail portion of the ground so there would be no contact with a box or other hot, but it's otherwise still a bare ground inside the sheathing.

The dryer plug is an old 50-amp style (no ground), and the water heater connect directly to the 2 hots and neutral, no ground either.

What, if anything, is wrong with using the bare ground as the neutral? I've seen mentions of insulation being required in the NEC and elsewhere but am unclear on whether it applies or what the real risk is here.

Dryer plug

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  • If you know a trick for getting rigid metal conduit laterally THROUGH 15 feet of joist, I'm all ears! It was replaced with flexible metal conduit so the drywall can be mounted directly to the ceiling joists instead having to be lowered to get under the existing metal conduit.
    – Laramie
    Apr 7, 2021 at 16:00
  • A-ha! I misread your post, apologies for that! (and the trick for that is to use short lengths of conduit and lots of couplers) However, have you considered that you probably can get a 4-wire run into that FMC (actual FMT is p. much a unicorn) if you used individual wires instead of NM inside it?
    – ThreePhaseEel
    Apr 8, 2021 at 0:47

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No, that's illegal and has always been illegal.

You are confusing neutral and ground, which is understandable since they go to the same place in the main panel. However they are actually different and separate; they are tied together in the main panel and that is the only reason they're allowed on the same bus. Don't let that confuse you.

The water heater actually needs 2 hot wires and ground. The water heater does not want neutral. So in that case, /2+ground is just fine. However, because the white wire is used for a hot, you need to re-mark the white wire with black or colored electrical tape on both ends.

However, the range actually requires 2 hots, and neutral, and it also requires ground if it is installed post-1996.

Even prior to 1996, it was never OK to use /2+ground cable as the 2 hots + neutral. So this work you recently did with 8/2 cable will have to be removed and re-done. Now prior to 1996 you could use SE cable or /3 (no ground) cable; however that ship sailed when Courtney Love was top of the charts.

Now your only option is to run 8/3 w/ground cable.

Further, you are now required to use a 4-wire connection with ground. So if the range is cord-and-plug connected, it needs to use a NEMA 14-50 socket and plug.

I'm sorry you have to redo it, but frankly, the "groundless" range connections are pretty scary. A simple problem with the neutral wire can electrify the chassis of the machine.

Lastly, "the last guy" used conduit. People don't use conduit unless they have to... so probably, you have to.

Another thing of note is that #8 THHN in conduit is allowed 50A, but #8 NM cable is only allowed 40A. So that #8 NM cable would need to be breakered 40A in any case.

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  • Or in other words: you might die or kill someone. Another great answer. +1.
    – JimmyJames
    Apr 7, 2021 at 19:58

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