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I recently found that the neutral bar and ground bar in my home's subpanel have no resistance (0 ohm) between them (when the neutral feed to the subpanel is disconnected). I root caused the symptom to one particular pair of neutral and ground wire. That leads to the junction box pictured below.

In the picture, you can see 3 wire nuts. The red ones each have 2 wires in it. The grey one has 3 wires in it: a thick wire (which I presume to be neutral), a bare aluminum ground, and a green wire. (EDIT: added this paragraph in case the picture is not clear)

I believe that the right thing to do here is to remove the neutral cable from the gray wire nut, and cap it off. I found the installation manual of the appliance, and the manual seems to support my belief.

But I'm a bit hesitant because the existing setup of the wire just seems too crazy. I wonder if I'm missing something. Is there any possibly valid reason that this junction box was wired this way?

My home is in California.

picture of junction box

picture of installation manual

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It was wired this way because Goober the appliance installer guy, whose job is pushing heavy appliances around on dollies, needed to hook this up and collect the customer's cheque ASAP. Goober had a 3-wire appliance to attach, and saw 3 wires in the wall, and boom zoom and out the door.

You actually have 4-wire service to this range. However it is in aluminum wire, which is a serious problem. If the ground is aluminum, surely so are the hots and neutral. None of those splice connectors are rated for aluminum wire.

You will need to obtain some "MAC Block" connectors, which are a somewhat miniaturized version of Polaris lug connectors, which are proven to work well with aluminum.

  • The two hot wires use a MAC Block to go from that aluminum wire to the corresponding copper wire from the range.
  • The aluminum neutral wire is simply capped off; one of those wire nuts is fine for that, but tape it on.
  • The aluminum ground wire goes to one side of the MAC Block. To the other side go 3 wires (which is allowed): the range's ground wire; a new jumper wire to the steel box; and a new jumper wire to a new hole in the cover plate. All need to be grounded.

... By the way, fix that schizoid lid.

On one hand, you've got a 4x4 junction box with a 2-gang mud ring that has 6-32 mounting screws in the correct positions to mount 120V outlets and switches. On the other hand, you've got a common 4x4 junction box lid that expects to attach to the corners of the box.

I see now that the junction box is blocked in by cabinetry. That isn't allowed and is a serious code violation: not only is it uncovered, but flammable materials are inside the box! Get a vibrating tool and cut away enough of the cabinetry above it that it's possible to mount a normal junction box cover plate the normal way. It looks like what's above that is nothing special, just the back of a drawer box or something, so it won't do any harm to remove the offending material.

Now you need a different lid that attaches to the 2-gang screw locations... a real electrical supply can help you out there. Home Depot won't have it, it's not popular...

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    Ah. I think I understand your comment about the lid now. I did not realize the mud ring is a separate piece from the junction box, and thus got confused about why you're talking about 3 pieces. I still need help with understanding your statement about conduit though. Did you type out that answer because you didn't see the bare ground wire, or was there something else I'm missing?
    – Haozhun
    Aug 21 '20 at 17:40
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    @Haozhun Sorry, I did not see that earlier. That changes the answer quite a lot, since it is also aluminum. On the junction box lid, WOW! It looks like somebody built cabinetry right across the junction box!!! You can't do that. That has to be torn out, sorry. Aug 21 '20 at 18:20
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    Note- you could bring in the pic on your phone, too. I'm sure that'll work in this post-dead-tree-edition world we live in. Oh, and when they return with the stuff you need, it'll probably be cheaper than the "HIC", but even if it's not, you're helping to keep a local business in business.
    – FreeMan
    Aug 21 '20 at 21:08
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    Did I miss the note that the macblock requires precise torque? A cheap torque screwdriver can be had for about $60; after that, the sky is the limit. Aug 21 '20 at 22:52
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    @aly post-NEC 2017, everything requires precise torque... Aug 22 '20 at 2:13

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