# Plumbing in Return Air Ducts



## jar546

Approved or not?  Why?

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## Pcinspector1

Plumbing or central vaccum line?

pc1


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## fatboy

No matter, plastic not allowed in CA returns......unless it is somehow listed that it can be.

I've heard, but not seen the listing, that there is a sprinkler pipe that has been list for CA retursn. listed


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## globe trekker

fatboy (and others),

Can you please cite the applicable code sections?



> why?


 Thanks!.


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## Gregg Harris

IMC 602.2.1 Materials within plenums


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## jar546

Pcinspector1 said:
			
		

> Plumbing or central vaccum line?pc1


I titled it plumbing because it is plumbing.


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## Pcinspector1

Thanks Gregg, I new it wasn't allowed but couldn't find it in the plumbing code due to the answer being in the IMC.

Pc1


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## mtlogcabin

Gregg Harris said:
			
		

> IMC 602.2.1 Materials within plenums


It is not a plenum it is a duct.

If it is a SFR then any material is allowed in a plenum. See exception #3 under 602.2.1.


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## RJJ

I agree it is not a plenum. My first ? would be has the design return capacity been changed, alter or reduced by the drainage pipe.

That would be assuming it is a drainage pipe! If it is an exhaust vent for a heater ???? what say you?

Last can not tell if there are cleanouts or connections associated with the pipe if it were DWV?


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## steveray

Did it meet the pressure test per IECC?


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## steveray

603.9 Joints, seams and connections.

All longitudinal and transverse joints, seams and connections in metallic and nonmetallic ducts shall be constructed as specified in SMACNA HVAC Duct Construction Standards—Metal and Flexible and SMACNA Fibrous Glass Duct Construction Standards or NAIMA Fibrous Glass Duct Construction Standards. All longitudinal and transverse joints, seams and connections shall be sealed in accordance with the International Energy Conservation Code.


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## RJJ

Well that is a good question? I believe Jeff was looking for if one would approve this install.


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## Gregg Harris

mtlogcabin said:
			
		

> It is not a plenum it is a duct. If it is a SFR then any material is allowed in a plenum. See exception #3 under 602.2.1.


I started to go with duct at first glance, but when the picture is enhanced it appears to be a cavity between two floor joists that has a sheet of duct board caulked to the edges of the joists. This would then make it a plenum and not a duct if that is the case the wiring would violate NEC  the wiring can run perpendicular to the long run.

300.22©

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.

 IMC 602.2.1Exception #3 does exclude plenums in one and two family homes, but I think this is an oversight since the prohibited point is that materials meet ASTME 84 or UL 723 for smoke and flame 25/50. PVC does not meet these standards.

Without a clearer picture it is hard to tell the distance the pvc runs in the joist span so support would also be an issue.


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## TheCommish

what about the electrical wires?


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## RJJ

The electrical wires can run perpendicular but are too close to the edge. If one considers it a plenum which the IMC would that the PVC is not permitted.


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## ICE

California code reads different than what I have seen quoted here.  CMC does not have section 602.2.1

California did not adopt the IRC mechanical sections.  So I should have stayed out of this thread.



> 602.2 Combustibles Within Ducts or Plenums. Materials exposed within ducts or plenums shall be noncombustible or shall have a flame spread index not greater than twenty-five (25) and a smoke developed index not greater than fifty.
> 
> Exceptions:
> 
> (1) *Return*-air and *outside*-air ducts, plenums, or concealed spaces that serve a dwelling unit shall be permitted to be of combustible *construction*.


The duct, plenum or concealed space can be of combustible construction.  Anything not a part of the duct, plenum or concealed space and not one of the eleven exceptions shall have a flame spread index not greater than twenty-five(25) and a smoke developed index not greater than fifty.

I seldom find DWV pipes but I do find a lot of condensate pumps.

http://www.homedepot.com/p/LittleGIANT-Nextgen-115-Volt-Condensate-Removal-Pump-VCMX-20ULS/203464514#.UdCis-uxPcI


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## klarenbeek

Is this in a single family residence? If it is, the IRC would apply, not the IMC.  IRC does not prohibit combustibles in joist return plenums, including pvc. The wires running parallel with airflow are prohibited by NEC, but any wires perpendicular to airflow are allowed.

 If this is in an apartment building, then the IMC does apply and both the pvc and wires are prohibited.  By IMC,  the wires need to be either in a conduit or plenum rated regardless of their direction in relation to airflow.  The IMC simply states all wiring exposed in a plenum needs to be plenum rated.


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## jar546

This is a SFR and the IRC applies in this case.


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## RJJ

So then IRC. The PVC pipe can remain. The wires need to be removed and are too close to the edge!


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## klarenbeek

That's the way I would call it (as long as the pvc is plumbing and not a vent for a High efficiency furnace or water heater). The other thing i might question is how the ductboard? is attached to the floor joists.  I don't think I would accept caulk as the means of securing it in place.  The foil facing should extend onto the bottom edge of the joists at least an inch and be stapled in place evry few inches.


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## RJJ

klarenbeek: The photo is not a straight forward as one may think. We see the pipe going in? or is it coming out? It is obvious that it is a return, but does the pipe turn up and drain fixtures for other floors. NII!


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## Pcinspector1

Would the ductboard have to be fire rated if thats the garage ceiling or house/garage wall? It has red tape?

pc1


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## RJJ

Can't read the tape! It looks like A-181 tape. I believe this is just a residential basement that is not conditioned.


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## klarenbeek

RJJ said:
			
		

> klarenbeek: The photo is not a straight forward as one may think. We see the pipe going in? or is it coming out? It is obvious that it is a return, but does the pipe turn up and drain fixtures for other floors. NII!


Hey now thats not fair trying to trick an inspector!  I'm not used to that. :grin:

You're absolutely right.  If its just passing through, its ok.  If the pipe turns up to fixtures above, at a minimum the holes through the floor would need to be sealed ase well, depending on whats above.

I think the tape is UL181A


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## Gregg Harris

RJJ said:
			
		

> So then IRC. The PVC pipe can remain. The wires need to be removed and are too close to the edge!


The reason for prohibiting the wiring from being in the plenum run parallel with the duct is the same reason that the pvc piping should not be allowed, it does not meet the ASTME 84 criteria 50 flame spread 25 smoke. The wiring when run the short span of the floor joist is considered to be a minimal amount of PVC exposure to fire where as the pvc piping if it had been conceived to be installed in a paned plenum would not be allowed. The volume of exsposed pvc of the piping is going to be a huge percentage above the wiring.

There needs to be a code change to prevent the piping to match the ASTME 84 standard that applies to material inside of the plenum/duct.


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## RJJ

I agree Greg! In this case the IMC would allow based on exception listed above.


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