NM running through a plenum

[gliebig (Gregory Liebig, CMI)]

Is there any “code” that allows a NM cable to run through a cold air return made up of two floor joists that are boxed in? The cable is more than 1-1/4" from the edge of the joist. I don’t have a picture as my battery died (a different electrical question :mad:)

[rmeier2 (Robert Meier)]

Yes it is permitted as long as the cable only runs perpendicular to the studs.

[tleahy (Tom Leahy)]

@Robert_Meier

Yes it is permitted as long as the cable only runs perpendicular to the studs.

This has confused me in the past. Are you saying this based on 300.22(c) and the way the return was built, not being specifically fabricated.

[gliebig (Gregory Liebig, CMI)]

@tleahy

This has confused me in the past. Are you saying this based on 300.22(c) and the way the return was built, not being specifically fabricated.

I’m guessing the exception in 300.22 (C) is what applies. This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.

[rmeier2 (Robert Meier)]

Yes, the NEC code reference would be 300.22(C)Ex. The NM cable can go through from one joist or stud to other but the cable cannot run parallel to the joist or stud.

(C) Other Space Used for Environmental Air. This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
FPN: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.
Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.