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View Full Version : Is the equivalent length of pvc fittings the same as metal duct?


cook42
10-06-2008, 10:44 AM
I'm putting in a 90% furnace in and I have a long run that might need some elbows. I want to make sure that I'm not going over the 10' rule by putting too many elbows on the flue pipe. Will someone please let me know if a 90 degree pvc elbow has the same equivlent length as a 90 degree metal duct? I thing that a 90 metal duct is rated at about 30 feet I might be wrong because I don't have my duculator with me!
Thanks
the dangling wrangler
10-06-2008, 11:29 AM
I'm putting in a 90% furnace in and I have a long run that might need some elbows. I want to make sure that I'm not going over the 10' rule by putting too many elbows on the flue pipe. Will someone please let me know if a 90 degree pvc elbow has the same equivlent length as a 90 degree metal duct? I thing that a 90 metal duct is rated at about 30 feet I might be wrong because I don't have my duculator with me!
Thanks

What does the installation manual say?
cook42
10-06-2008, 11:57 AM
What does the installation manual say?I can't have no more than 3 elbows and the length cannot exceed 10'.
t527ed
10-06-2008, 12:26 PM
run larger pipe if needed.
larobj63
10-06-2008, 03:00 PM
I can't have no more than 3 elbows and the length cannot exceed 10'.

Really? That's pi$$ poor.
sparksandfan
10-06-2008, 03:04 PM
PVC and sheet metal have different friction coefficients. Your Manual D will show that.
the dangling wrangler
10-06-2008, 03:10 PM
run larger pipe if needed.

That's what I'm thinking.
ga-hvac-tech
10-06-2008, 03:10 PM
Read the installation manual carefully and do NOT exceed it's design. Failure to follow the installation manual in this area can lead to overheating the HX (heat exchanger) and seriously shortening the life of the furnace... it also may lead to increased gas usage to heat your home.

Note that when the tech guy from the distributor comes out to look at why the HX failed early, he/she will see the wrong PVC piping and may well void the warranty.

Cheating on PVC vent piping is not a wise choice IMO.

Note also that if the tech guy from the distributor comes out, he/she will ask who the licensed installer is, and where the unit was purchased... If positive proof of purchase by a licensed contractor through an approved distributor is not verified; there may well be NO warranty at all.
gary_g
10-06-2008, 03:12 PM
What happened to:

"No DIY. Get Pro membership. Thread closed"?
the dangling wrangler
10-06-2008, 03:17 PM
What happened to:

"No DIY. Get Pro membership. Thread closed"?

That guy, has the day off.
gary_g
10-06-2008, 03:19 PM
That guy, has the day off.

Nah, he's just taking a long lunch break. :)
t527ed
10-06-2008, 03:21 PM
What happened to:

"No DIY. Get Pro membership. Thread closed"?



don't think that line has been crossed......................yet.:cool: