I was recently in my Crawlspace installing a doorbell transformer when I got the idea of potentially reusing an existing junction box.

The only problem is the junction box currently has a lamp holder mount and is being used as lighting for the Crawlspace.

Does anyone see any issues with me having the transformer mounted to the box? (See attachment).

Note: I obviously wouldn't tap into the light power I would run a separate line from a new circuit, just using the junction box for convenience.transformer

  • 4
    If the power comes in to the fixture (always hot) and loops out through a switch loop then tapping that power is actually better than getting it from another circuit because (a) don't have to run another circuit and (b) less of an impact on available space in the box. If you pull in another circuit then you may find you run out of space (cubic inches). Jan 26, 2022 at 2:45
  • How is this fixture switched? Jan 26, 2022 at 4:45
  • 2
    That's how the doorbell transformer is done in my house, and it's been fine for 35 years or so now. The way mine is hooked up is power comes into the box first, and then a switch loop is run to the room switch, so the xformer always has power.
    – Milwrdfan
    Jan 26, 2022 at 5:04
  • 1
    I presume the screws mounting the lamp base had been loosened to remove it to look inside and that the lamp base was simply put back for the photo and will be tightened back down when the work is completed, correct?
    – FreeMan
    Jan 27, 2022 at 13:33

1 Answer 1


Believe it or not that would meet code today if GFCI protected, the GFCI protection was added because of the chance of breaking the bulb and getting shocked. Depending on year built that Romex or NM is probably 14-2 if prior to 2000 it could be 12-2 as that was about when they started color coding, did the fixture have a pull cord? Coming out of the hole? Today a switch close to the entry is needed with the GFCI I read the comments and see it is a few years before switching and GFCI’s were required.

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