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A friend wants to install a tankless water heater under the kitchen sink for faster hot water and plans to use a 40A circuit near the sink that is meant for an electric range. The house was built in the 90s, so the wire to the range is 8/3 with no ground.

The tankless is a pure 240v device and is adamant about requiring a ground, so it requires two hots and a ground. Now, I know that electrically, he has 3 wires available for the device, and the neutral goes to the same place as the grounds. The heater will work, and it should be safe, but is there a reason to not just use the neutral in place of a ground?

Aside from the wire being white instead of green, what are the problems with this install?

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  • Which version of the Hillbilly Electrical Code do y'all use? Cooter Sez... or Ma Granpappy Always Did...? – Harper - Reinstate Monica May 12 '20 at 18:35
  • @Harper-ReinstateMonica, it's more of a "what could go wrong" issue. Hard to justify running a new wire (which would be very hard in this case) just because of the color. Can the 8/3 be safely and/or code legally used in this case? – JPhi1618 May 12 '20 at 18:38
  • Seriously, though, "8/3 no ground" would be difficult to source in the 90s. They didn't keep making it just for ranges; the Code exception that allowed it was for suppliers to use up their old stock. Are you sure there's no ground wire? – Harper - Reinstate Monica May 12 '20 at 18:38
  • @Harper-ReinstateMonica, I thought it was more common? Yea, for sure no ground wire. It has a black cover, paper rolled spacers and a red, black, and white wire. – JPhi1618 May 12 '20 at 18:43
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    Sometime in the mid 90s is when they banned the 3-wire range connections, which would make /3nognd utterly unsellable. And it was no secret the ban was coming, this had been talked about for decades and stalled by the appliance industry. Cable makers knew. So I have to guess it was "old stock" some electrician had hoarded and was in a hurry to use up :) – Harper - Reinstate Monica May 12 '20 at 18:50
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There's a weird little ... glitch ... in Code that I don't know what to make of. Except such exceptions rarely make it in by mistake, and certainly don't survive two editions by mistake.

The glitch says this: Neutral wires must be naturally white* their entire length, even in concealed parts of a cable. And if ground wires are green** insulated, then ditto. However, ground wires that are bare only need to be bare where visible.

Code seems to be tipping the hat to annihilating wire insulation at all places it is visible, and calling a wire (of any color) a ground.

This action is irrevocable; once this is done, it can never again be used for the "formerly grandfathered" role of a 120/240V split phase range.

A more versatile method would be to retrofit ground from that location to anywhere with a #10 or larger homerun, including the Grounding Electrode System or any metal conduit.

* or gray or colored with 3 white stripes

** or yellow with green stripe

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    I guess this would include stripping off the white in the breaker panel and attaching it to the ground bar instead of leaving it connected with the neutrals... Not using it for a range is fine, it's actually just a gas cooktop in that location. Any larger kitchen remodel that would bring in a place for an electric oven or similar would also make running new wire more possible. – JPhi1618 May 12 '20 at 18:49

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