I am starting a bathroom remodel second story that requires a length of NM wire to be lengthened by a few feet. I realize I can't do this hidden in a wall or floor and need this done in accessible junction boxes. This is not a big problem because I have sheetrock down and can mount two boxes with the wire extension between them. One of these boxes would be in an out of view place and would just have a blank cover on it and be completely accessible. Without doing some fairly major surgery, the second box is in a terrible place and would stick out like a sore thumb. Right where the second box could easily go is right next to the HVAC forced hot air supply duct and register.

My question. Since I have the sheetrock off and access to the outside the of the rectangular supply duct can I legally: 1) cut a hole in the duct for a junction box 2) put a wood brace in the wall outside of the duct and mount a box sideways to that. The box opening would be flush with the outside of the duct 3) put a mount a metal cover over the JB inside of the duct 4) put the register back on

Hope that makes sense.... In this scenario, at the end of the day, there is a junction box that has an accessible metal cover inside metal HVAC duct. The box itself is not in the duct, just the cover. This cover can be accessed by taking off HVAC register

Thanks in advance for any guidance or suggestion

Hope I did pics correctly! Image with the duct work is where I would like to put a JB. The blank cover plate would be on the left inside side of the duct itself and the box would be mounted sideways in the wall. Then the register goes back over the duct and hides the cover.

The existing wire is in the floor about 18" in front of the wall and pops up thru floor as shown in second pic.

Second image is where I am too short. There used to be a drop in jacuzzi type tub in this section so there was no issue.

I have an opening in the floor where the tub drain used to be. I want to cut the wire there, run one end to the where the duct is and come up thru floor base plate to new box. Take remaining wire on other end and run thru studs as far as it goes (should get me close to corner and out of sight) and put in second box. Then tie those together with third wire

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    Hello, and welcome to Home Improvement. Where in the world are you? And, a picture of the presumed poor box location could be helpful. – Daniel Griscom Mar 23 '19 at 16:23
  • Thanks for the feedback. I added pics (hopefully correctly!) I am located in New Jersey USA – ChuckP Mar 23 '19 at 20:03
  • In the second image, where are you trying to get those cables to go to? Also, I take it they are coming up from a joist space, right? – ThreePhaseEel Mar 23 '19 at 21:02
  • They go to a sunken family room. They are coming up from the second story floor thru joists and into a roof truss (non accessible) of the sunken room and all the way across the room. One goes to a switch for gas fireplace and other is from a switch to an outside flood light on the corner of the house. My plan was to cut wire, run thru studs as far as it will go to right and put in JB there (well hidden). Take other end (it will reach) and and mount JB as described with cover inside duct hiding it. Seems anything different will either be butt ugly or major surgery which I'm trying to avoid – ChuckP Mar 23 '19 at 21:14

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