Plumbing in a return plenum

[elgato]

Is it "OK" to have plumbing ( or wiring, for that matter ) in HVAC ducts? Couldn't condensation occur as cold water runs through the plumbing while warm air runs through the duct? Of course winter air is very dry, but there could be situations in the transition months.

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[Scottpat]

Is it "OK" to have plumbing ( or wiring, for that matter ) in HVAC ducts? Couldn't condensation occur as cold water runs through the plumbing while warm air runs through the duct? Of course winter air is very dry, but there could be situations in the transition months.

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Nope! Nothing but air should be in that return.

[Robert Jones]

Hey at least they added spray foam.

[Brandon Whitmore]

Wires can pass through:

From the 2006 IRC.

- - E3804.7 Air handling—stud cavity and joist spaces. Where wiring methods having a nonmetallic covering pass through stud cavities and joist spaces used for air handling, such wiring shall pass through such spaces perpendicular to the long dimension of the spaces.

I tend to remember that distribution pipes can pass through as well. Scott, do you have a code cite for the prohibition of pipes through the return?

I do have issue with a drain line passing through, and if it is not covered by the IRC, it should be. I'd have to look it up, and am too lazy right now.

[Bain]

When it comes to electrical wires in return ducts created by attaching pan metal or ductboard to floor joists, the position of my local AHJ is that the wire can be installed perpendicular to the floor joists, but not parallel with the joists.

Do you NEC guys know whether this is actually addressed by the code, or is it some sort of skewed interpretation?

[Bain]

Wires can pass through:

From the 2006 IRC.

- - E3804.7 Air handling—stud cavity and joist spaces. Where wiring methods having a nonmetallic covering pass through stud cavities and joist spaces used for air handling, such wiring shall pass through such spaces perpendicular to the long dimension of the spaces.

I tend to remember that distribution pipes can pass through as well. Scott, do you have a code cite for the prohibition of pipes through the return?

I do have issue with a drain line passing through, and if it is not covered by the IRC, it should be. I'd have to look it up, and am too lazy right now.

We were typing at the same time . . . though in my defense, I was also eating dinner and watching the news.

[Brandon Whitmore]

We were typing at the same time . . . though in my defense, I was also eating dinner and watching the news.

I just figured I didn't count as an NEC guy, since I posted info. from the IRC [:-dunce]

[Scottpat]

Wires can pass through:

From the 2006 IRC.

- - E3804.7 Air handling—stud cavity and joist spaces. Where wiring methods having a nonmetallic covering pass through stud cavities and joist spaces used for air handling, such wiring shall pass through such spaces perpendicular to the long dimension of the spaces.

I tend to remember that distribution pipes can pass through as well. Scott, do you have a code cite for the prohibition of pipes through the return?

I do have issue with a drain line passing through, and if it is not covered by the IRC, it should be. I'd have to look it up, and am too lazy right now.

No, I don't have a cite.

But, I bet it would fall under the parts about the duct fire blocking, ASTM C 411(has to do with flame spread and how hot things can get before they start to smoke), ASTM E 84 (flame spread) and a few other items...

[Chad Fabry]

Copper has a flame spread rating? I bet it exceeds foil faced rigid ducting. Here's the down side to copper in the plenum.... it gets hot enough in the plenum to burn the copper releasing water and extinguishing the fire.

Wait, that's not a down side.

[Tom Raymond]

So that's the new IRC sprinkler requirement[]

Tom

[Brandon Whitmore]

Nobody ever came up with the code cite for not allowing drain lines to run through a return-- anybody?

I'll have to look it up later today if nobody knows the cite for sure, since I just ran into it today.

[robert1966]

I will follow back for more info, as I have seen wiring and plumbing thru the returns....

Thanks,

[genduct]

My understanding that only pipe NOT allowed is GAS pipe. water or even DWV should be OK.

For the record, the new ACCA MAN D discourages the use of building cavities for returns. Couldn't outlaw it because it is still ok in IRC