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I would like to install two switches in the same gang box, but each switch would be on a separate circuit. The issue I have is that the two circuits originate from separate subpanels.

Is this OK to do?

Normally I would splice the switch/receptacle grounds from different circuits together in the gang box when they originate in the same subpanel, but since the two circuits come from different subpanels should the grounds also be separate?

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  • One problem is when work needs to done on one switch. The other switch will still have power from the other sub panel and very few if any people would check for a breaker in another panel to turn off. In the same panel you could at least have handle ties for two breakers to be safe.
    – crip659
    Nov 20, 2022 at 13:36
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    Is there a good reason you can't put them on the same circuit?
    – JACK
    Nov 20, 2022 at 14:17

2 Answers 2

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Having multiple circuits from different panels in the same box is fine

It's not at all abnormal or uncommon to have multiple circuits from different sources (different panels, different voltages, even different services altogether) in the same junction box. Simply keep their neutrals separate, and tie all the grounding wires together. (If you're using a metal box, you may wish to land the grounds on the box separately on each side of a divider, that way the next person to work on this can't readily screw it up by tying neutrals from two different sources together.)

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  • What about retrofit ground rules? My understanding is if you have a device with no ground (no ground wire or suitable metal conduit) that you can grab ground from another circuit but only from the same panel. If you had one device from a panel with ground and one without ground available from a different panel, in the same box, and you tied grounds together that would give you a ground but to a different panel. Nov 20, 2022 at 15:19
  • @manassehkatz-Moving2Codidact -- that's true, but I don't think retrofit grounds are in scope of the P's question Nov 20, 2022 at 15:24
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    You say this is common .... in residential? Certainly if you consider two services to be common we have different definitions of common. But even two panels ... it exists, sure, but is it common? I ask because I think if it's uncommon, easily avoided, and presents new dangers, it should be avoided even if it's allowed.
    – jay613
    Nov 20, 2022 at 15:46
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    We've gone from "not uncommon" to "not impossible". Not the same bar. But my point is if it might take future homeowners by surprise it ought to be avoided if possible. Perhaps if the two subpanels are adjacent and used only for space, they can be imagined as one but if one of the subpanels serves the garage, or the pool, or the extension then running a circuit from there to a part of the house served buy another subpanel and sharing a junction box there IMO should be avoided even if it's allowed.
    – jay613
    Nov 20, 2022 at 16:13
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    Agreed re 320 svc. In fact I have that, two main panels right next to each other and their circuits both go throughout the house. I've so far avoided OP's situation. The smaller panel has lots of room so if I supply a system or renovate a room from the smaller panel I supply the entire system or room from it. This avoids mixing and slowly creates space in the full 200A panel.
    – jay613
    Nov 20, 2022 at 17:36
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I suggest two separate, and adjacent 1 gang boxes rather than a single 2 gang box. THAT would definitely separate the two circuits at the switches.

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    Is there any reason to use two separate boxes instead of a two gang box with a divider? Nov 21, 2022 at 2:33

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