Home>Discussions>ELECTRICAL & LIGHTING>Can you run NM wire thru a cold air return duct?
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rickpantel
Can you run NM wire thru a cold air return duct?

We need to run NM electrical wire in the ceiling from an unfinished area of the basement through to another room. The problem is that the adjoining ceiling between the two rooms has been sealed off (with plywood) so that there is no easy route to run wire from one area to another. The ceiling joists underneath the plywood run directly across the intended path of the wires.

However, there is a cold-air return duct from the heating system running between the two rooms....it would make a perfect and easy conduit for the wiring. Is this a safe thing to do?

JLMCDANIEL
Re: Can you run NM wire thru a cold air return duct?

No, any knick could electrify the duct and the wiring is not protected if someone at a later time cuts into the duct work.
Jack

Re: Can you run NM wire thru a cold air return duct?

NM cable is not plenum rated. No cable is to be run in a duct. There is alot in the nec that I have not stated.I have not read this section in the latest code it might be some exceptions. I recal in a older code you could run it I think horizontal through the return. Someone on here might have more info. For your application the answer is absolutly no.try fishing the wire near a plumbing vent might give you a straight shot up to the attic

rickpantel
Re: Can you run NM wire thru a cold air return duct?

Thanks for the replies. This house is circa 1949, and looks like it was owned by the worlds cheapest home handyman before us. There are so many electrical code violations that an inspector would have apoplexy if he saw them all! What I am trying to do is clean stuff up as much as possible to make it safe until we can completely gut the basement, put on an addition, and re-do all the wiring and plumbing properly.

That said, I don't want to make a bad situation worse. I'm willing to take some shortcuts, knowing that it is temporary, but only if they are safe. I'll try to fish the cable through an alternate routing, but it won't be easy.

Gray Watson
Re: Can you run NM wire thru a cold air return duct?

Rick,

It might be helpful if you updated your profile to include your location, which if I recall correctly is BC Canada. Unfamiliar with Canadian restrictions am unable to address your specific question.

canuk
Re: Can you run NM wire thru a cold air return duct?

The Canadian Electrical Code and possibly the NEC had an exemption which allows you to route NM 90 through a cold air return that is an enclosed stud/joist cavity ..... The joist cavity that is covered with sheet metal or a stud cavity covered with plaster or drywall ..... used as a cold-air return for a forced warm-air central heating system.

However ...... it can only pass through perpendicular ..... not along the inside distance of the cavity.

This does not apply to a dedicated metal duct run for this purpose.... in other words you can't puncture a hole in the metal ducting to run electrical wires without special consideration.

This exemption may not be allowed in your area or it may be required to use BX90 cable for this ..... you would need to check local code.

Hope this helps. :)

rickpantel
Re: Can you run NM wire thru a cold air return duct?

Yes, Gray...it is BC, Canada.

Thanks for the reply, Canuck....I remember something in the Code about running crosswise thru a wood/metal duct. I was thinking about running along the length of the ducting, but thought better of it after reading the responses. In the end, I managed to get a fish tape through an alternate route, and all is well.

Thanks for the answers, everyone. :)

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