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enter image description hereWould it be possible to add #10AWG GROUND from another branch (hot-water heater 30A circuit) in order to retrofit ground and replace a 3-wire receptacle with a 4-wire one to be able to use it for an induction range that came with a 4-wire (2x6AWG + 2x8AWG) cord/plug?

This is the receptacle: Help Identify 3-wire SE cable

I'm aware of the GFCI solutions to this problem from another posts but I'm worried that the induction range might be too sensitive with that setup.

On the other hand, I'm trying to avoid to run entirely new 4-wire 6AWG from the panel.

This is on a 50A breaker.

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  • That is a very interesting comment. I've researched this topic and read through related posts and did not come across "bare wire as neutral" scenario
    – Matt
    May 1, 2022 at 23:58
  • Yes, see diy.stackexchange.com/questions/236291/… for quoted NEC that allows it and other location options. Also note details in option (4). May 2, 2022 at 4:55
  • Glad I didn't make it an answer. Per Harper's answer, my comment is completely wrong.
    – DoxyLover
    May 2, 2022 at 6:19
  • @DoxyLover If the comment is wrong, please delete it so subsequent readers won't be misled. May 2, 2022 at 18:02

1 Answer 1

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Yes, retrofitting a ground is fine if you're not extending the circuit to a new location. Take care that the new ground wire does not contact the existing neutral, you might want to "make it an insulated wire" with some shrink tube to sleeve it.

SE cable has a bare neutral, that is how it is made. Read the Chapter 3 rules for it, you have the right to re-designate it as a ground. But no obligation.

You cannot retrofit a neutral.

#10 copper ground suffices for conductors with capacity up to 60A.

Yes, the ground can come off any junction box that has #10 Cu ground going back to the same panel the circuit comes out of. Bare copper is fine.

You could use #8Al ground but would be difficult to splice to the water heater ground, and is an odd duck you might not find easily.

The receptacle must be rated for 75C thermal to get 50A out of #6Al. Also it must be rated for Al wire. Most are, but make sure.

There are two tricks to working safely with aluminum.

  • Using terminals properly rated for aluminum is the first one (glares at UL and their blunder in the 1960's, too hastily rating 15A receptacles for aluminum without proper testing).
  • Torquing connections to spec. (this science was only discovered quite recently, and on copper connections - but we can safely assume it is important on aluminum too).

The cheapest way to get a torque screwdriver is to get a 1/4” drive "beam type" torque wrench. Either use Allen sockets, or "drag link" for flat-blade, or a "bit holder" adapter for 1/4" hex screwdriver bits.

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  • Any shrink tubing rated for #10AWG would be fine to "make it an insulated wire"? Will there be torquing specs listed on the receptacle or in the manual that comes with? I do have a torque screwdriver so no worries there, but thanks for the tip To reiterate, it's fine to use #10 AWG ground splice, even though on the range's end it will be 2x6AWG and 2x8AWG?
    – Matt
    May 2, 2022 at 2:06
  • Will the new ground wire use the same receptacle knockout (bottom) as the Al 3-wire, or will it have to be clamped from the back via the other knockout? I have a feeling there will be only 1 clamp provided per receptacle
    – Matt
    May 2, 2022 at 2:15
  • My local box store has 50A receptacle but it doesn't list thermal rating other than: Wire type: Copper/Aluminum and "Flammability Rating is V-2 per UL94" which I looked up and is not the rating I'm looking for: "V-2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed."
    – Matt
    May 2, 2022 at 2:41
  • Also no torque spec listed on the site. The other brand I see online at other big box store says: 25 inch pounds
    – Matt
    May 2, 2022 at 2:44
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    @Matt #10Cu or #8Al ground. No rating means 60C rating. It's not that obscure... Look for it to be etched into the receptacle itself. "Cu/Al" and "75C". Torque likewise will most likely be on the receptacle itself. May 2, 2022 at 2:45

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