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gordy
03-05-2005, 12:05 PM
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy
dash
03-05-2005, 12:21 PM
Doesn't meet the specs of class 1 ,duct,Flame and smoke developed rating.

If there's a fire,not a good thing.Some codes allow it under a concrete slab,little fire danger.
gordy
03-05-2005, 12:46 PM
That makes sense to me. So how does flexible duct get around this? Is it the insulation?

Gordy
dmoneyc22
03-05-2005, 12:49 PM
i believe there is a type of duct system that is of pvc type construction you may want to contact your local dealer for info
dash
03-05-2005, 12:56 PM
Originally posted by gordy
That makes sense to me. So how does flexible duct get around this? Is it the insulation?

Gordy

Just a different material,than PVC,there is a type of PVC that meets this rating,very expensive though.
tinner73
03-05-2005, 01:20 PM
Originally posted by gordy
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

there is pvc coated spiral duct. i don't quite get your question. what do you want to do?
tinner73
03-05-2005, 01:21 PM
Originally posted by tinner73

Originally posted by gordy
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

there is pvc coated spiral duct and rectangular. i don't quite get your question. what do you want to do?
framehvac
03-05-2005, 01:33 PM
Originally posted by dash
Doesn't meet the specs of class 1 ,duct,Flame and smoke developed rating.

If there's a fire,not a good thing.Some codes allow it under a concrete slab,little fire danger.

Thats only for the first 5 feet.I think the price would be to much.

[Edited by framehvac on 03-05-2005 at 02:19 PM]
gordy
03-05-2005, 01:56 PM
Well, I want to install AC in my attic for a 2300 square foot ranch. Looked into Hi Velocity turned off by the reduction in seer rating. So thinking conventional. Not an avid fan of flexible ductwork. Just wondering about the pvc duct work, an avenue that went through my head knew there must be a reason why not widly used.

I have read alot about ductwork in unconditioned spaces. I know its not my best option. But its doable. If done right. I have ceiling radiant heat (hydronic). My concerns with the ductwork would be A. Condensation in the winter or summer, leading to mold issues. B. Lack of performance, ductwork being warm/ hot between cooling cycles leading to longer than needed cycles.

This system would only be for AC. So I'm tryin to get my ducks in row here. Thinking of using two air handlers so I can keep my attic center unobstucted for storage. The ranch is a U shape. HeatGain 40,000 Btu high side. I presently use 30,000 Btu's worth of window shakers and it cools they handle the load.

Thanks for your replies Gordy
dash
03-05-2005, 02:17 PM
The heat gain for the ducts in the attic,should have been accounted for in the Manual J,load calculation.Use an R-8 insulation,to reduce the loss.
tinner73
03-05-2005, 02:26 PM
any kind of ductwork can be done. it depends how thick your wallet is. i would use standard galvanized metal that would get wrapped on the outside. i too dislike flex systems, Dash would disagree with me.
framehvac
03-05-2005, 02:45 PM
Originally posted by tinner73
any kind of ductwork can be done. it depends how thick your wallet is. i would use standard galvanized metal that would get wrapped on the outside. i too dislike flex systems, Dash would disagree with me.

Its a southern thing tinner73.

[Edited by framehvac on 03-05-2005 at 03:09 PM]
tinner73
03-05-2005, 03:08 PM
i understand.:D
andrew boyce
03-06-2005, 05:23 PM
It is all about the gass released when the stuff melts or burns.

PVC is will release toxic gasses that will cause you to die before you can get away from the fire..


AB
framehvac
03-06-2005, 05:50 PM
Originally posted by andrew boyce
It is all about the gass released when the stuff melts or burns.

PVC is will release toxic gasses that will cause you to die before you can get away from the fire..


AB
Most everything in your house andrew boyce released gass when it burn.Plummers use it to in house.

This is pvc duct

http://www.nature-sys.com/images/PVC%20DUCT/SYSTEM25.jpg


http://www.nature-sys.com/images/PVC%20DUCT/SAW2.jpg
square2round
03-06-2005, 07:10 PM
Originally posted by framehvac

Originally posted by andrew boyce
It is all about the gass released when the stuff melts or burns.

PVC is will release toxic gasses that will cause you to die before you can get away from the fire..


AB
Most everything in your house andrew boyce released gass when it burn.Plummers use it to in house.

This is pvc duct

http://www.nature-sys.com/images/PVC%20DUCT/SYSTEM25.jpg


http://www.nature-sys.com/images/PVC%20DUCT/SAW2.jpg

First time I've ever seen this type of PVC duct. Can it come in any rectangular size? I assume this is designed for underground slabs? Besides being used underground, what other applications would it be used in? That would have to be expensive. It's not like you can fab this in the shop.

I've only dealt with the PVC coated spiral duct for underground.
framehvac
03-06-2005, 07:22 PM
Any,its just all about saving the money that is why no one uses it.It's not like you can fab this in the shop you could do it,you would just have to learn how & get some new tools for the shop.
framehvac
03-06-2005, 07:24 PM
http://www.nature-sys.com/images/PVC%20DUCT/install.jpg


http://www.nature-sys.com/images/PVC%20DUCT/PVC/EX1.jpg
framehvac
03-06-2005, 07:25 PM
gordy
Member

Registered: Feb 2003
Posts: 11
Is there any reason as to why there is not a use of PVC for ductwork applications for HVAC?

Gordy

So they do,do it.:D
andrew boyce
03-06-2005, 07:36 PM
True.. but in the infinite wisdom of the US government they have decided to rate some types of materials more of a risk when burning or melting than others... this is the reason that the PVC ducts you have in those pictures are most likely designed with low levels of this gas...

I feel that if one attempts to breath anything that is burning you will likely die. so what’s the point. Best thing to do is get out of a burning house or structure as this in it self is likely to result in death.. LOL

:-)

AB
tinner73
03-06-2005, 07:45 PM
they do make pvc-coated sheets of iron. it can be run through fab machines like regular galvanized and formed into regular rectangular pipe and fittings. i'm sure it ain't cheap. we used it in some medical building, i don't recall exactly, it was quite a few years ago. i do remember that the finished product seemed to have alot of the coating worn off after running it through the machines. ANYTHING is possible if you have the money.
square2round
03-06-2005, 07:52 PM
I bet that pvc coating on flat sheets does come off easily, especially in the brake...or beading it. I'd like to go and see how they make the pvc coated spiral duct...or even the spiral itself.
ct2
03-06-2005, 08:53 PM
What about using spiral pipe? The cost is reasonable, somewhat cheaper than fab ducts and much better than flex
tinner73
03-06-2005, 10:09 PM
the spiral is made off a small coil. my last shop made it.
framehvac
03-07-2005, 01:32 AM
Originally posted by andrew boyce
True.. but in the infinite wisdom of the US government they have decided to rate some types of materials more of a risk when burning or melting than others... this is the reason that the PVC ducts you have in those pictures are most likely designed with low levels of this gas...

I feel that if one attempts to breath anything that is burning you will likely die. so what’s the point. Best thing to do is get out of a burning house or structure as this in it self is likely to result in death.. LOL

:-)

AB



andrew boyce what do you do for a living because some of you information is way off or I am just reading it wrong?
gordy
03-07-2005, 05:47 PM
Thanks for answering my question people. I was just curious now I know. God for bid the ductwork catches on fire. I agree if one gets out with out choking from the foams, carpets,plastics ect. in a home. Makes a fire rating on ductwork a mute point if you ask me.

Gordy
framehvac
03-07-2005, 05:53 PM
Originally posted by gordy
Thanks for answering my question people. I was just curious now I know. God for bid the ductwork catches on fire. I agree if one gets out with out choking from the foams, carpets,plastics ect. in a home. Makes a fire rating on ductwork a mute point if you ask me.

Gordy


That right gordy.Its the first 5' of duct that they make a fire rating on.
framehvac
03-07-2005, 05:56 PM
j
dash
03-14-2005, 06:20 PM
Originally posted by framehvac

Originally posted by gordy
Thanks for answering my question people. I was just curious now I know. God for bid the ductwork catches on fire. I agree if one gets out with out choking from the foams, carpets,plastics ect. in a home. Makes a fire rating on ductwork a mute point if you ask me.

Gordy


That right gordy.Its the first 5' of duct that they make a fire rating on.

It's all the duct in our area.

Makes it a mute point?Think of what happens ,with even a very small fire,in the duct and the fan is on.