Electrical Code question

[George Bokros]

I am in the beginning stage of a bathroom remodel. I took down the fixture over the vanity and was surprised to find the fixture not mounted to a box. It looks like there may have been a box since there is a round hold in the drywall for the box. Interestingly the same stud cavity is also a cold air return. My cold air returns on the second floor go up into the ceiling and down a center of the house drop to the basement.I am guessing the HVAC guy took out the box so he could close off the stud cavity to use as the cold air return but that does not explain whey the drywall has a hole like a box would have been there.

Is this an acceptable installation according to code??

[Ken Fitzgerald]

I doubt seriously it would meet code. I don't think any device capable of starting a fire can be installed in a duct. I could be wrong.

[Tom M King]

Get an "old work" box that can mount in the hole. Caulk all the openings so there is no air leaking, and it should make no problems.

[George Bokros]

I found a pancake box that is 1/2" deep. I can screw it to cold air return bottom. I will caulk with silicone caulk all screw holes that are on the cold air return side to seal the electrical from the duct.

I am guessing that since the fixture had to be moved off center of the wall on order to center it over the vanity the electrician removed the box. The new vanity is larger than the old one so center of the wall where the box was is now in the correct location over the new vanity.

[Steve Baumgartner]

It sounds like there may be two things wrong. First, I believe a box is mandatory. You can't simply route wires into the fixture through a hole in the wall. Second, it wasn't completely clear from your post whether the wire feeding the fixture runs through the same space as the air return. I believe that special "plenum" rated cables are required for anything that runs inside an air feed or return, since burning insulation can release toxic fumes into the plenum.

[Tom M King]

I didn't understand that there was a metal duct in there. I thought that the stud cavity was being used for a duct. I've never done it, but have run into it more than a few times.

[George Bokros]

The wire does not run through the cold air return. The wire is below the cold air return bottom. I plan to install a pancake box and then go into the cold air return from the other side and install a sheet metal boot to close off the access to electrical.

[George Bokros]

I didn't understand that there was a metal duct in there. I thought that the stud cavity was being used for a duct. I've never done it, but have run into it more than a few times.

There is no metal duct, it is just the stud cavity being used as cold air return.

[Steve Baumgartner]

I didn't understand that there was a metal duct in there. I thought that the stud cavity was being used for a duct. I've never done it, but have run into it more than a few times.
I don't think it matters whether there is a metal duct or not. The issue is that the fumes from burning insulation would be transported by the air system to the rest of the building, creating a serious health hazard.

[Brian Elfert]

Here is what the National Electrical Code has to say on the matter: NEC 300.22 Type NM cable shall not be installed in plenum spaces, but may be installed perpendicular through joist or stud spaces used as such. That is from a 2 page document listing the most frequent issues/questions for residential wiring in the state of Minnesota. The statement from the NEC is as clear as mud on if wiring can go through ducts or not.

When I wired the house I had built in 2001 it was mostly the first sub there could run their stuff where they wanted and future subs had to work around what was already installed. That said, I tried to anticipate where ducts might go so as not to run wire there.

[George Bokros]

Here is what the National Electrical Code has to say on the matter: NEC 300.22 Type NM cable shall not be installed in plenum spaces, but may be installed perpendicular through joist or stud spaces used as such.

Yup clear as mud. Kind of defeats the issue raised about toxic fumes doesn't it?

[roger wiegand]

First, I believe a box is mandatory. You can't simply route wires into the fixture through a hole in the wall.

I'm not sure this is true, as long as the wire enters an approved fixture with appropriate clamping, etc. Our inspector had no issue with, for example under- and over-cabinet wiring that exited the wall and went into an attached light fixture designed for that purpose. I don't know the code, but the electrician roughed it in that way and the inspector approved it. I think the wire needs to be protected, anchored, and connections made inside an accessible box, but which side of the plaster that box is on may not matter.