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When we remodeled our basement, we wanted to move a switch that controls 4 lights. Here is what I think happened: The electrician spliced in a single piece of romex, so that the black wire runs to the new switch location, and the white wire runs back and connects to the other end of the cut black wire.

The wires are not marked, but it seems unusual to see a SP switch with one white wire and one black wire, coming from the same piece of romex?

I attached a tracer/tone generator, one lead to each wire - nothing. I attached the red lead to the "white" wire, and the black lead to the ground - nothing. I then attached the red lead to the "black wire," and the black lead to the ground - nothing.

Thoughts?

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    Did you remember to operate the switch when you had the wires connected to the tone generator?
    – JACK
    Commented Feb 26, 2021 at 2:03
  • Can you post a photo of the inisde of the old switch box? Commented Feb 26, 2021 at 2:35
  • What are you trying to accomplish? Just figuring out your wiring? Installing a new switch, fixture or outlet? What's the goal here? Nothing wrong with "gaining knowledge", but your ultimate goal could help drive an answer toward your needs. Also, pictures of both ends of the suspect wiring would help immensely.
    – FreeMan
    Commented Feb 26, 2021 at 12:36

1 Answer 1

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It's not unusual at all, it's just a switch loop

When using off-the-shelf cables, if you're in a situation where you don't need neutral but do need another hot, it is perfectly legitimate to re-task a white wire for that purpose. That is allowed in cables.

However it violates Code in 2 ways.

First, when a white wire is re-tasked to be a hot, it must be marked at both ends to indicate it has been reused as a hot wire.

Second, when a switch loop installed post-NEC 2011 adoption, a 3-wire+ground cable must be used so neutral can actually be brought to the switch location.

The practice of using a /2 cable and not marking white is a throwback to the 1990s.

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  • Thank you all for your responses, and yes, some additional detective work after reading these did help me to determine that I have a "switch loop/leg." It is most definitely not marked at the switch end, and is a two wire + ground cable. I cannot tell if it is marked at the line end, because I haven't found that, although I see the cable go through a bottom plate (this is in a basement). I verified this by 1) shutting the breaker, testing the wires with my meter, connecting the black and white wires (which would have been connected by the switch anyway, and turning the breaker back on.
    – Dylan
    Commented Feb 26, 2021 at 22:10
  • No surprise, the lights came on. I then turned off the breaker, disconnected the black and white wire from the first light in the series, and connected a test lamp. Breaker on, test light on. So that's step one of what I want to do. The next step is to add dimmable troffers to replace old flourescent troffers. To do this requires a 0-10v dimmer, and for that I need to run low voltage wiring in addition to the 120, and have the right dimmer.
    – Dylan
    Commented Feb 26, 2021 at 22:11
  • The right dimmer requires line, load and neutral (and ground plus purple and gray), so I am thinking of running a new romex cable, the kind that now includes black,white, ground on one side, and purple and gray on the other, from the first lamp in the series to the new dimmer (which will be in the same location). To do this, I would have to leave the switch leg in place, permanently connected with a wire cap. Maybe you will say that is not a good idea, but I I guess the alternative is to completely disconnect the old circuit from the breaker, and run a new wire from there.
    – Dylan
    Commented Feb 26, 2021 at 22:12
  • For that, I most definitely would want a licensed electrician. Here's the thing: a licensed electrician has quoted $2800 to replace the 6 troffers and wire everything up, and I don't think he even knows about the switch leg. The lights are about $60/each, dimmer about $70, and cable able $90 for 200 ft, which is 125 feet more than I probably need, but I can't find lesser quantities. I realize that any of you who are professionals are probably aggravated by this, and I typically have a licensed professional do everything but the most minor of jobs, but this just seems like a big difference.
    – Dylan
    Commented Feb 26, 2021 at 22:12
  • sorry. one more: replacing the wiring starting at the breaker is actually not an option, because it isn't just lights but also outlets, and if I disconnect at the breaker, the outlets won't work. ugh.
    – Dylan
    Commented Feb 26, 2021 at 23:23

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