I am doing a DIY 400A service upgrade and I would like to get some vetting on my work before the utility connects it and the city inspects it. The meter/main combo is outside behind this wall of the garage and I have drilled through the wall to install the nipples you see. The wires will go from a breaker in the main panel to a subpanel in the garage. I ran three 1/0 XHHW-2 wires and a 4 AWG XHHW-2 (aluminum) for the ground. The wire supplier apparently did not have bare aluminum conductor.

Junction Box

Is this lookin good? Of course I need to pull the wires a little more so they fit comfortably inside the box. I am starting to think I need to ground the box. If that is the case, can I just remove a little insulation from the existing ground wire without cutting it and clamp a small copper wire that goes to the box?

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    Yes ground the box. Carefully strip a ring around the ground and use a lay in lug. It's a little to bolt to back, so probably best to bolt to bottom of box, Scrape off paint behind the lug. Lay in lug: duckduckgo.com/… Commented Feb 4 at 0:58
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    So you're feeding the garage <= 120 amps then? Since it's 1/0 wire. Commented Feb 4 at 2:27
  • @NoSparksPlease thanks for reading my question and taking the time to comment. May I ask - your seems a complete answer, why write it in a comment? I am looking up those lugs and I hope to find them. Stripping a ring of insulation out of the wire is going to be annoying but if it is deemed useful I will do it in order to do a good job. Commented Feb 4 at 3:19
  • @Harper-ReinstateMonica I guess... "yes"? I am not sure what the real question is however and how it pertains to this box. Are you suggesting it is not big enough for these wires? Can you rephrase? It's a box I got ouf of zoro.com, 12x12x6 inches Commented Feb 4 at 3:21
  • @NoSparksPlease can you tap the box and screw the lug to it rather than scrape paint?
    – jay613
    Commented Feb 4 at 5:23

1 Answer 1


If you are using metal conduit, that counts as the ground. Just make sure the conduit nuts are tight enough to bite through the paint on both sides.

Reference: https://steeltubeinstitute.org/resources/equipment-grounding-using-steel-conduit

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    I'm sorry the picture should have been clearer - both the nipples and the conduit going to the subpanel are 2in PVC. Commented Feb 4 at 4:22
  • Can you swap the PVC with EMT? If not, then you'll need to add a ground wire. This could be a separate ground that only grounds the box to the main panel's ground bar, or you could loop through like @nosparksplease mentioned.
    – Pants
    Commented Feb 5 at 16:21
  • It would be a lot of work to replace that and honestly I don't want to as PVC conduit is fine in my jurisdiction. I will just run a scrap piece of wire to ground the box to the other side into the ground bar in the panel. Commented Feb 5 at 16:32

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