NM-B in Air Returns

[A/A Fuel GTX]

Where can I find the requirements for NM-B installed in cold air returns? I know we run perpendicularly through them all the time in residential settings but I'm wondering where the vertical issue is addressed. I looked in 300.21/22 but maybe I missed something.

 

[walton]

300.22 ex. Install NM cable either vertically (ceiling) or horizontally (wall) as long as it is perpendicular (right angles) to the plenum, joist or stud spaces.

 

[Dennis Alwon]

Not sure what you are asking but 300.22(C) excepttion is clear. You can traverse the plenum either horiz. or vertically as long as it is perpendicular to the long dimension of the space.

300.22 (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.

 

[rookie4now]

300.22(C) refers to "other space" not covered by 300.22(A) or (B). If you are talking about an actual plenum and it is for enviornmental air, I believe you need 300.22(B)

 

[Dennis Alwon]

Would a panned cold air return count as other space. I was under the impression it did and I was assuming that was what the OP was asking about.

 

[raider1]

A panned off stud or floor joist cavity or would not be a plenum but an "other spaces for environmental air" in accordance with 300.22(C).

Chris

 

[MichaelJ]

does 300.22(c) Exception not apply to nometallic covered cable

 

[raider1]

does 300.22(c) Exception not apply to nometallic covered cable

Yes, the exception to 300.22(C) does apply to nonmetallic sheathed cable in dwelling units.

Chris