How do I make a 3 wire splice with 2/0 wire? I want to tap into a service panel feed to add a subpanel.

  • What is enclosing this splice, or is it a direct burial application? Jan 20 '17 at 2:35
  • Also, are you splicing copper or aluminum wire? Jan 20 '17 at 2:49
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    Usually done with large split-bolt connectors, or "gurneys". Kinda sounds like this would not be a "subpanel", if you are tapping into the wires feeding the service panel. It would be another service panel, no? Jan 20 '17 at 7:14
  • Not a fan of the split bolts. You have to smother them in electrical tape, and that makes them hard to inspect. I agree something is odd; this is only used in rare and specific situations, and I would have expected him to mention that. These little short tweet-sized questions leave you wondering. Jan 20 '17 at 7:26
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    I don't like the sound of this at all! You DO NOT simply "tap into" the service panel wires. You put the sub-feed conductors on a circuit breaker. Jan 20 '17 at 12:30

Are you sure this is the right thing to do? It's rather unusual. If you are feeding a subpanel from a main panel, there would be no call for doing a 3-wire splice, you put a circuit breaker in the main panel and feed the subpanel off that.

You would only use a 3-wire splice off the top of the panel in the rather unusual situation of having 2 panels of equal rank; i.e. two main panels. The new panel would never be called a "subpanel" unless the panel you're tapping off of is already a subpanel. And the panels would be right next to each other. In those cases, you'd use either screw-down splice blocks, or dual lugs.

It's difficult to infer skill from a question the size of a tweet. What concerns me is that you have the common case of adding a subpanel to a main panel, and you are freestylin' because you know that little about how this stuff works. I certainly hope not.

You use a breaker that snaps into the regular breaker spaces below the main switch, and you feed the subpanel off that. It may be quite a large breaker, which may necessitate moving even more circuits. Don't same-pole any MWBCs (and if you don't know what that means and why, you are out of your depth, and no, googling MWBC won't complete your knowledge.)

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  • Your answer is spot-on Harper, but I'd be wary about including the second part, about splicing. Nothing about the over-simplified original question sounds correct. Simply adding double lugs to a main panel is almost never the right thing to do. Jan 20 '17 at 12:33
  • CO/ALR is only for wiring devices -- the equivalent rating for terminals is AL7CU or AL9CU Jan 20 '17 at 12:43
  • @SpeedyPetey you are quite right. Emphasis changed. Jan 20 '17 at 16:03

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