Must penetrations for NM thru air returns be sealed?

[bsf]

Must penetrations for NM thru air returns be sealed?

Is there a code requirement, or is it good practice, to seal penetrations into panned air returns? I am talking about returns formed by attaching sheet metal to the bottom of joists. Assume that the panned air returns in question are not part of a firestop. I ask because of the derating implications of running NM cable through a hole that is ?fire- or draft-stopped using thermal insulation or sealing foam?. I cannot find anything in NEC about the requirement that this penetration be sealed; only derating if it is sealed. Maybe it is addressed in residential mechanical code. I do not want this to turn into a discussion on derating. Derating of NM passed through holes in studs/joists w/ or w/o caulking and/or foam has already been thoroughly discussed. Thanks.

 

[mdshunk]

That panned in return is going to leak 20,000 other places, so I've never felt the need to seal the holes from a romex passing through.

 

[charlie]

I agree with Marc . . . Uh Oh . . . did I really say that? :smile:

 

[frizbeedog]

I agree with Marc . . . Uh Oh . . . did I really say that? :smile:

You have 10 minutes to change your mind....wait, you're a mod. Take your time. :smile:

 

[c2500]

Is it even legal anymore to allow an air return in that manner?

c2500

 

[stickboy1375]

Not recommended thats for sure... But I still see it done every once in awhile.

 

[Dennis Alwon]

I would not penetrate a plenum duct unless I did seal the hole. Codes around here are very strict about sealing the duct so why should I be allowed to break their codes.

 

[c2500]

I am digging through 2006 IRC and it appears to be legal for returns only. I can help but think that the leakage would be so massive that the energy code would prohibit that type application.

c2500

 

[bsf]

I am digging through 2006 IRC and it appears to be legal for returns only. I can help but think that the leakage would be so massive that the energy code would prohibit that type application.

c2500

I have looked through both NEC and my state?s 2003 residential code. The closest applicable section I have found is M1601.1.1(7.3) in the residential code: ?Stud wall cavities and joist space plenums shall be isolated from adjacent concealed spaces by tight-fitting fire blocking in accordance with Section R602.8.? That does not apply as the adjacent spaces are not ?concealed?. I think this question is beyond the realm of NEC. I may just call an inspector tomorrow.

 

[SmithBuilt]

Is it even code to run a non plenum rated wire thru a duct?

 

[raider1]

Is it even code to run a non plenum rated wire thru a duct?

Take a look at the exception to 300.22(C). This section permits NM cable to be run perpendicular through a cold air return in a dwelling unit.

Chris

 

[bsf]

For what it is worth, I talked to one of my local building inspectors today. I would rather have talked to a mechanical inspector. However, the building inspector said the holes must be fire-stopped. He was busy, so the conversation was short and I did not get a code reference. I do not think I really got his full and undivided attention. shrug

 

[kjw444]

I always fire stop when going through a cold air return. Also, when a switch box must be mounted in a cold air return, I use a 4sq box and sleeve the nm with flex into the next stud cavity.

 

[William1978]

300.22 (b) will help you with your question.

 

[Dave_B]

Is it even code to run a non plenum rated wire thru a duct?

I was just thinking the same thing. Nothing can be in there unless it is there to sense or act upon the air.

 

[mdshunk]

I was just thinking the same thing. Nothing can be in there unless it is there to sense or act upon the air.

Save for the fact that the code permits it under certain circumstances. Perpendicular in resi.

 

[raider1]

300.22 (b) will help you with your question.

300.22(B) is not the section you use when dealing with a stud space used as a cold air return in a dwelling unit. 300.22(C) is the section that deals with residential cold air return built using a floor or stud cavity. Take a look at the exception to 300.22(C).

Chris

 

[Jonathan Bilby]

Hey. My first post here.

International Energy code 403.2.2
All ducts, air handlers, filter boxes, and building cavities used as ducts shall be sealed.

The IRC does not prohibit NM in the return air plenum of a single family dwelling as far as I know, but the IMC does require "plenum rated wiring" within return air ducts.

 

[Dennis Alwon]

Hey. My first post here.

International Energy code 403.2.2
All ducts, air handlers, filter boxes, and building cavities used as ducts shall be sealed.

The IRC does not prohibit NM in the return air plenum of a single family dwelling as far as I know, but the IMC does require "plenum rated wiring" within return air ducts.

Welcome to the forum.

Yes but the nes does make the exception as noted above. It must run perpendicular to the return and as noted above must be sealed.

 

[bsf]

Thanks for the comments. No surprise; I am dealing w/ a residential situation where panned air returns span the entire width of a basement. This question probably would have been better asked in an HVAC forum, but as I hinted in the OP my concern is basically derating. In the absence of clear code guidelines, I am just going to span the width of the returns w/ EMT and snap-on bushings and then fire-stop around the EMT. Number of NM cable and derating will no longer be a concern.