I have a bit of an odd situation. I have a standard outlet (120v, 15 amps, just a normal United States receptacle). I'd like to run some raceway conduit up from the outlet*. At the other end of the raceway, I'd like to have some 12v lights. I'd also like to have these lights use a 12v dimmer switch. The dimmer is pretty standard. It goes into a normal one-gang electrical box, and takes 12v + GND in, and gives 12v + GND out (but the output is dimmed). Here's how it is wired:

Wiring diagram

Image taken from the Amazon listing, and archived with the Wayback machine to be safe.

Anyways, my original idea was to just get a standard wall-wart 120v AC to 12v DC transformer, stick it in the outlet, and then mount the switch in a raceway box like this one, and run the raceway up from it (so the transformer plugs into the outlet, and the 12v end goes into the box, say, via a hole drilled into the bottom of it, with the raceway box being a bit above the outlet).

Wiremold box

I was thinking, though, it would be nice if I could just remove the outlet, put the box extender right where the outlet is, and then have the switch in the box extender. But, in order to do that, I would need 12v going into the in-wall box. I've seen doorbell transformers, but they appear to mostly take 120v from in the box, and make it into either 12v or 16v outside the box. But I'm wondering if there is a good (code-compliant and useful) way to do the opposite: take the 120v from outside the box, and make that into 12v in the box, effectively making the box into a low-voltage only box, to avoid the "no high and low voltage in one box" rule. Is there a good way to do that?

*The outlet is just mounted like a normal standard outlet (in the wall, the faceplate sticks out maybe a few millimeters).

  • Are you prepared to remove your current single-gang box which holds the existing outlet and fit "something" wider in its place in the wall?
    – brhans
    Commented Jan 12, 2022 at 19:42
  • @brhans I'd still like to use my raceway, so that would need to be able to connect to a one-gang raceway box. I would certainly be open to it, but if it was difficult, I might get an electrician to do it for me. But if you have an idea, I'm open to it!
    – cocomac
    Commented Jan 12, 2022 at 20:15
  • Generally when this is done in new construction, they put a large box in a closet and the large box has a 120v outlet. The large box can then contain a transformer that is plugged into the outlet and the low volt wires can be spliced into the wire coming out of the transformer and distribute the low voltage. Commented Jan 12, 2022 at 20:18
  • I do like that idea, but this isn't new construction. Would replacing the outlet with a blank, mounting a transformer to the top of the box that used to have an outlet it it, and then putting in a low-voltage box a few inches above it, which I'd have the raceway box mounted on work? Mind you, I have no idea what type of box the outlet is in. @FreshCodemonger
    – cocomac
    Commented Jan 12, 2022 at 20:21
  • 2
    FYI about the image hosting: when you add an image StackExchange automatically clones the image onto imgur; its availability from the original source/host becomes irrelevant. Archiving the image to wayback doesn't matter: StackExchange still makes its own copy on imgur and the posted question links to that, not to the wayback URL you supplied when posting the question (or answer).
    – Greg Hill
    Commented Jan 12, 2022 at 21:39

1 Answer 1


All you need is a plug-in power supply of a slightly different form-factor, one you're not used to.

You're used to wall warts where they have an integral low-voltage cord. That cordage is not legal to run into a wall mounted junction box.

Instead, get a "wall wart" that has screw terminals for its low voltage DC output. Come off that with thermostat cable. That's all made for on-wall or in-wall use and is free to enter junction boxes.

  • To clarify, on the 120v box/the original box, I'd install a 120v AC to 24v AC doorbell transformer, and then I'd run a wire from the doorbell transformer up a bit to a second box that would contain a 24v AC to 12v DC converter, and then I could just put the raceway box on top of that, and run my LEDs off of that (using thermostat wire for the 12v DC run, within the raceway). Is that correct?
    – cocomac
    Commented Jan 13, 2022 at 0:01
  • @cocomac no, that's not correct -- you want a 120VAC to 12VDC "wall wart" that has screw terminal outputs Commented Jan 13, 2022 at 0:58
  • @ThreePhaseEel Like this one?
    – cocomac
    Commented Jan 13, 2022 at 1:03
  • @cocomac -- that's just a standard barrel plug wall-wart with a barrel-plug to screw-terminal adapter Commented Jan 13, 2022 at 1:04
  • @cocomac -- what you're after looks like this Commented Jan 13, 2022 at 1:05

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