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So I have this electrical box that is housing 2 switches, one of which isn't currently controlling anything, the switches aren't even grounded either, so I'm getting rid of the useless switch and cleaning up that box.

The power enters the box from the 12/3 cable at the bottom right of the box (both red and black are already hot entering) and then from that box there are two 12/2 cables, one going to outdoor lights, and the other one to the doorbell chime box.

For reference, here is the current box, so that right switch is not currently serving any purpose since red and black are already hot coming in. (I'm sure I could re-wire the previous 2 receptacles in the circuit correctly as to have that switch control them, but I don't use them so I'm not interested in that, I'd rather remove that switch altogether):

enter image description here

Here is how I'm planning to re-wire it (and yes, I will also use a wire nut to properly tie all ground wires), and I mapped the full circuit for reference, a few receptacles before this box, and it is not a MWBC, 12/2 from the breaker box, the 12/3 only starts from the third receptacle :

enter image description here

This looks right to me, but would appreciate a sanity check. Thanks!

isherwood
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Dord
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2 Answers2

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First, as far as the mystery switch, that usually controls receptacles. One of two things is likely the case:

  • It controls a receptacle, but you never checked for that. (you may have a "matching" dead receptacle that you never thought to try with the "dead" switch turned on... why would you?)
  • It used to control a receptacle, but a novice changed receptacles and didn't know what they were doing, and shorted out the switch by not "breaking off the tab" where that is required.

Now as far as your drawing, that looks alright, but a multi-wire branch circuit is providing 4800 watts of power for about 25 watts of total load, which makes no sense to me. Are you sure you are not mistaken about that circuit? Are you sure it only powers the one light? Have you turned the breaker(s) off and searched the house for what else died? I would expect it to power at least receptacles in 1 room, or a lot more lights.

It does not need to be wired as a MWBC (and probably shouldn't be, as the 15 watt doorbell transformer can easily coattail on an ordinary circuit. To remove its MWBC character, the black and red could be pigtailed to a single wire, and that wire can be landed on the breaker.

Keep in mind that a "single breaker" with two independent handles is not a single breaker at all, and is the absolute worst possible place to put a MWBC, i.e. that's how you set your neutral on fire.

Harper - Reinstate Monica
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So the black and the red wire are hooked up together at the 3rd receptacle is what you are saying. It has to be. So just disconnect the red wire at the 3rd receptacle, strip it off and label it copper ground and connect it with the copper ground there.

And do the same up here at the junction you are working with. Strip it off and connect it to the copper ground.

No need to feed a new wire at all.

Feed the door bell ( as you say) with the black wire which was actually done of course and therefore been working and there has not been any fire or explosions. That is certain.

So whoever wired it like this shows two reason why it was wired like this.

It is the only wire he had, no copper ground. He did not have a cover with one opening for the one switch only, the cover had two opening for two switches.
He had another switch. So he simply used that extra switch to fill in the opening on the cover. So it ended up a dummy fill in switch.

That is what my insight tells me.

Over and out. :-)

Meta_Alchemy
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