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My old house’s main panel has two ground wires, one leading to pipes, another to a grounding rod. Because the bottom is the only easily-accessible side for new circuits, and because most of the knockouts are in use, I’d like to combine the two grounds into one and connect them together in a junction box in the crawlspace. I’m pretty sure there’s no code or safety issue in doing this, but I wanted to double-check.

Here’s a photo of the two ground wires. They go to two different places on the neutral/ground bus bar. I propose removing one and connecting it to the other in the crawl space. Each is run in its own flex MC conduit.

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One question: any chance I could just cut away some of the flex and bond the two together, or does it need to be done in junction box?

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2 Answers 2

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No can do. Those are your Grounding Electrode System wires, and those cannot be spliced by any craft that we here possess.

Crimping them legally requires specialized kit only an electrician is going to own due to the high up-front costs.

However, they can come into a box and routed through conduit if you have the spare length and sufficient conduit cross-section, or brought in one shared knockout hole with appropriate clamp.

I see some conduit pipes with only 1 circuit in them. If able, I would install junction boxes not far below the panel, and fork circuits out of those boxes so they are fully using the capacity of the conduit entries.

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  • Yeah, I was already going to run more circuits through existing conduit to junction boxes, hoped I could do the same with the grounding.
    – Rick
    Sep 23, 2022 at 0:55
  • So, I could conceivably run a single continuous ground wire to wherever these two go, and use that instead, right? And I don't think those require any special tools; I've seen grounding electrode clamps that just have a screw to bond them.
    – Rick
    Sep 23, 2022 at 0:59
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    @Rick sure, if copper is no object. Terminating those wires at the ground rod is nothing special. It's inline splices that need the unobtanium tools. Sep 23, 2022 at 1:14
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Grounding wires must be continuous from the main panel to each of the places they are going (ground rod and water pipe, same as in my house). As I understand it (and I went through this recently with my electrician as part of a heavy-up) only certain very limited types of connections are allowed - basically a type where they can't really be "undone". In other words, no wire nuts, Polaris or similar connectors.

To the extent that if there are two ground rods then the wire is continuous from panel to first rod to second rod, or if (as my electrician did) the water pipe bound is in two locations (before and after the original main shutoff valve) it is continuous from panel to first connection to second connection.

Thinking about it very practically, anyone doing work on your electrical system or who accidentally does something - oops, I cut this copper wire, what is it? - should not be able to do anything "normal" that would disrupt the grounding system. Disconnecting a ground wire in the main panel or at the ground rod or water pipe would be clearly "abnormal" so you would deal with it appropriately. But a junction box in the crawl space? That is a different animal. If someday someone is doing work and finds this box, they may have no idea what the purpose is and might check for voltage (none when nothing is going on with the grounding system) and disconnect wires to get them out of the way. On the other hand, if you find a big thick bare copper wire snaking through the crawl space, you will hopefully search until you find one end (main panel) or the other (ground rod or water pipe) and realize what it is and not disturb it.

But getting back to the actual problem: not enough knockouts. That is a solvable problem. You can cut additional holes as needed in the panel enclosure. You can also probably double up - two cables through a single knockout, provided the cables are small enough and the knockout large enough.

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