Re: Electrical through a cold air return
The only way I see this being permitted is if the cable is run through solid steel conduit where it passes through the duct. The penetrations where the conduit goes through would need to be sealed, and the conduit would likely need to be somewhat oversized; the ends of the conduit would need to remain open on at least one end to allow airflow through the conduit -- depending on circumstances, it may need to be sealed on one end for fire protection. (Oversized and open would prevent heat buildup in the wire. Even though it's a cold air return, a cable encased in conduit can heat up from the current flowing through it.) The conduit should be fitted with bushings at each end to protect the cable from abrasion.
Be sure to run that plan by your inspector BEFORE starting the work. Sometimes they will approve a solution that is normally in violation of code IF you've taken pains to mitigate the problems the code is intended to address. You'll need a detailed drawing, and if the inspector approves, the drawing needs to be stamped or signed by the inspector to ensure final approval.
Another option is to use conduit but rather than going through the duct, route the conduit below or around the duct. This will satisfy code requirements that prohibit running cable along the bottoms of the joists or outside of a finished wall. It might not be as pretty, but it will certainly pass inspection.
Last edited by Fencepost; 11-22-2013 at 04:37 PM.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.