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I'm remodeling a kitchen and I need to junction 14 gauge wires for a lighting circuit that are near impossible to get to or re-route. Is it permissible to junction 14 gauge wires in the same box with a 12 gauge dining room receptacle? Just to be clear, I won't be co-mingling #12 and #14 wires on the same circuit, I'm only going to have them in the same box.

Also, I know the rules about how many wires can be in a certain box. I was thinking about using 4S metal box with a mud-ring to ensure I have plenty of space.

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  • I think that's acceptable, but not sure, so I'm not posting this as an answer and will let others with more knowledge chime in. I think the bigger issue is having two circuits in the same box, but even that I think is allowable. We'll see what the big 3 have to say. Jan 23 at 15:12
  • In the meantime, you might want to take the tour of SE. It's a great site, no BS allowed, just serious Q/A stuff, lots of experts here that generously contribute their knowledge. Here is a link to the tour: diy.stackexchange.com/tour Jan 23 at 15:15
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Having multiple circuits in one box as fine, as long as you don't cross the streams!

What you propose (i.e. having a 15A circuit share a box with a 20A circuit) is entirely fine and normal. There is one thing you'll want to be careful about though, and that's not crossing the streams; while you'll need to connect all the grounding conductors together, you need to keep not only the hots, but their partner neutrals rigorously separate to avoid overloading neutral wires, tripping GFCIs and AFCIs, and spewing stray magnetic fields everywhere.

You'll also want to mark the wires as to which circuit they come from; they make labels designed for this purpose, even, if you want a professional-looking solution for that.

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    Yes, you can have any number of circuits share a junction box (subject to fill limits of course), but you must mark the wires in some way to distinguish the different groups. The size difference is "a kind of" marking :) Jan 23 at 18:12
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    @Harper-ReinstateMonica As someone who's enough of a casual to perhaps not be able to immediately distinguish 12 and 14 in a cramped, dark box, I suggest that not using obvious tags might result in your offspring's being included in hasty imprecations. Jan 24 at 5:10

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