PVC in plenum

[AusLee]

Hello,

I have a room with false ceiling, with HVAC ducted supply to diffusors but no ducted return: the plenum is used for this purpose.

NEC 300.22 (B) says i must use EMT tubes in this area, however i have PVC tubes that are marked "LSF, non-propagation of flame". Can i use those?

 

[waross]

Probably not. The issue is not just flammability, but an issue of toxic fumes from hot plastics in the return air plenum. The fumes could be distributed throughout the building by the HVAC system.
respectfully

 

[BJC]

NO. Everything in a plenum has to be "Plenum Rated".
PVC is not rated, in a fire it generates phsogene gas. Firemen don't like that.

 

[alehman]

Plenum-rated CPVC plumbing piping is available. I wonder if there is CPVC conduit.

 

[AusLee]

Thank you for the info.

Alehman - what is the difference my electrical subcontractor likes 7" sewage pipes more than anything for infrastructure

 

[alehman]

The main similarity between conduit and pipe is that they are both round and have hole in the middle. Conduit is made and tested in accordance with electrical conduit standards. Compatible fittings must be used. I've seen plumbing elbows (and even ball valves!) used in conduit, but it's not advisable. Also conduit listed and labeled for electrical use. It would be in violation of most electrical codes to use plumbing pipe as conduit, esp 7"!

 

[waross]

Actually, rigid conduit is made to the same dimensions as schedule 40 water pipe. There are additional requirements for conduit. Welding flash must be (and sometimes is) removed from the inside of the conduit. The inside of the conduit must be galvinized or painted.
Rigid PVC conduit is the same dimensions as scedule 40 PVC water pipe. The PVC conduit has an additive in the plastic formulation to make the conduit more resistant to sunlight.
respectfully

 

[itsmoked]

Many times I have seen ABS run thru buildings for electrical stuff (NOT POWER). Phone, cable, networks, etc. They use the sweep turns and tees.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com