Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations pierreick on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

PVC in plenum

Status
Not open for further replies.

AusLee

Electrical
Sep 22, 2004
259
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?
 
Replies continue below

Recommended for you

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
 
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.
 
Plenum-rated CPVC plumbing piping is available. I wonder if there is CPVC conduit.
 
Thank you for the info.

Alehman - what is the difference :) my electrical subcontractor likes 7" sewage pipes more than anything for infrastructure :)
 
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"!
 
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
 
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.-
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor