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I am redoing all my electric (some details here: Is my new electric/subpanel plan correct?) - all of the cables currently in the house will be eventually disconnected, but (due to staples in hard-to-reach places, etc) I don't plan on necessarily removing/ripping them out.

I have a switch in the bedroom and a switch in the office that... I haven't been able to identify. It's right where a light switch would be, but there are no ceiling-mounted light fixtures and I've tested every outlet - none of them are controlled by it. The switch appears to be wired in a switch loop - see the picture below.

Switch wired as switch loop

I need to remove this junction box (to install a larger one and the new switch/cable) - what should I do with this wire? It will eventually be disconnected (when I switch over to the new panel), but while it might not be right now, would it be safe to cap the individual conductors separately and shove it into the wall cavity to "kill" it? I'm not sure where it connects to, so tracing down the other end will be difficult, maybe impossible if it doesn't come up into the attic. I measured voltage across the switch (with it both on and off) and from each conductor to ground (assuming the box is grounded, which it might well not be) and only picked up phantom voltage (11V or less).

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    Have you pulled out the outlets in that room? There may be a half-switched one that was replaced once but the tab on the hot side wasn’t broken. If you check the switch and both wires are hot with the switch off, that would confirm it (the tab would back-feed the switched hot wire).
    – DoxyLover
    Commented Feb 22 at 1:23
  • That's a good think to double-check, though the outlets are all quite old - unlikely that they've been changed since the switch (but not impossible). I'll take a look at the outlets to see if I can find one that's tied to this switch - though (for the purposes of this question) I'd rather operate under the (worse/more difficult) assumption that I can't find it.
    – user112697
    Commented Feb 22 at 2:01
  • Before you pull out the outlets, check the switch wires. If one wire is cold with the switch off, then that’s not it.
    – DoxyLover
    Commented Feb 22 at 2:36
  • @DoxyLover I measured the voltage across both wires with the switch on and off - when it was on I got 0, and when it was off I only got phantom voltage, ~11V.
    – user112697
    Commented Feb 22 at 3:20
  • Then I’d say that it is not a case of a missing tab on an outlet.
    – DoxyLover
    Commented Feb 22 at 5:35

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No you cannot just put a nut on a wire and shove it back into the wall. Why? What happens if you accidentally knock that nut off while installing the new box and don't notice? That's why. Plus code requires that all wire junctions/terminates be permanently accessible with nothing more than a screwdriver to remove a cover plate.

You'll have to pull that cable into your new box & cap it off there.

You can plan to remove the wire from the box once you identify the other end and disconnect it from whatever it's connected to there, so maybe screw the box into the stud instead of nailing it in to make that easier. In the meantime, though, to remain code compliant, the cable must terminate in the box.

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  • As a point of clarification, at the time I disconnect the old panel, all the wires to it will be 100% de-energized. At that point is it kosher to "destroy" the wire even if I don't know the location of the other end?
    – user112697
    Commented Feb 24 at 0:23
  • So long as you know that both ends are disconnected, they can be left hanging in the wall. Not required, but might be a nice thing to tag is as "abandoned" or "disconnected both ends" for future generations.
    – FreeMan
    Commented Feb 24 at 13:19

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