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I'm adding a #8AWG bare ground in order to retrofit a 3-wire range socket into a 4-wire one. I will be splicing into an existing water heater circuit to get the "at least #10" ground that is needed. Kitchen is on the other side of this wall and to the left and that bare ground will be exposed in this garage closet.

Since there's no j-box in the closet, I will need to add one to be able to splice into this circuit. Do I need to use a whip or a NM Schedule 80 liquid tight conduit? If so, I would combine it with this j-box:

BUT HOW DO I RUN THE BARE COPPER OUT OF THAT BOX? enter image description here

More details about tapping into existing circuit and background to this question: Is it possible to add a retorfit ground wire to a (3-wire) Type SE, Style U cable from another branch?


1 Answer 1


More like "how do I bring this up to code?"

Random $1 4x4 steel junction box. (should be $1, Home Depot is overpriced).

Cable clamp appropriate for 10/2 wire. x2.

"10/3" wire whip. (it's like cordage, the /3 counts the ground). I prefer the kind with a screw-down conduit nut, not a fidgety clip that is "one shot" and you can't easily correct if you do it wrong.

If you don't like the price of wire whip, then feel free to make it using either a) AC/MC cable with appropriate cable clamps for a 1/2" knockout, remember the redheads. Or b) FMC conduit with appropriate connectors to go in a 1/2" knockout, and THHN wires inside the FMC. If you have a quality lumberyard who cheerfully sells all that by-the-foot, that's the way to go.

Think about where the stud is. Choose a knockout on the back of the box that will let the existing Romex come straight in the back. Install the cable clamp "backwards" there (conduit nut side out, clamp side in, clamp oriented to give you best access to the clamp-down screws).

Bap down the conduit nut with a screwdriver and hammer (what the crowns are for) and thread the Romex through the cable clamp and slide the box down til it hits the wall. Fasten box to stud with random 1-1/4" deck screws (I prefer Torx or Robertson, but you do you).

Cut the Romex cable so the length coming out of the box is a little less than 12 inches. Strip at least 6" of sheath off the Romex (leave at least 1/4" past the cable clamp). Remember to tape/re-mark the white wire as red (any color but green or gray will do, but think "red").

Little #10-32 machine screw goes onto the ground screw on the box. Romex ground goes around that 180 degrees (little more), tighten down ground screw, leave remaining Romex ground as a pigtail. By the way, I buy these at a good hardware store for 15 cents each either green, or just a silver one out of the screw bin. But shop where you like.

Bare ground wire comes in side knockout via a second cable clamp.

Wire whip comes in another side knockout. Goes to water heater.

Either a nice huge tan or blue wire nut, or an "accessory ground bar intended for service panels" as a method to splice all these wires together. Crank it to the limits of human strength.

Finally, a simple blank cover and you're done.

  • I don't think the 3/8 in. Non-Metallic (NM) Twin-Screw Cable Clamp be able to hold a bare #6 ground that is only 0.162" What type of clamp did you have in mind?
    – Matt
    May 3, 2022 at 15:27
  • This type of ground bar? homedepot.com/p/…
    – Matt
    May 3, 2022 at 15:38
  • Is there any concern for the bare ground wire being run so close to the garage sink?
    – Matt
    May 3, 2022 at 15:40
  • 1
    You don't want the ground "in the sink", but otherwise shouldn't matter much. Remember, ground only carries current in a fault situation. If it were a metal sink, for example, connected to copper pipes then it would actually be connected to your ground all the time. May 3, 2022 at 16:19
  • 1
    @Matt Yeah, a bar like that but I'm used to seeing $3-4. Prices have gone nuts, at least at box stores. Haven't talked to my electrical supplies lately because this is a bad time to do projects so I'm not doing them. The cable clamp will close tight enough, the 3/8" figure isn't about cable opening, it refers to the size of the knockout... but but it's a weird historical artifact because the KO is actually 1/2" trade size. Which is 7/8" LOL. May 3, 2022 at 19:38

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