High Eff. Furnace venting

[kungfuparachute]

I have recently had three different contractors out to see about switching to a high efficiency furnace. Two said they could do the horizontal vent and one said he could not due to a crowded joist space and the distance of the run. (9" joist height over 24') Is the quarter inch drop per foot the standard on the vent, and are there exceptions? I can't quite get that on 24'. What is the maximum distance the vent can run? Also, there is only room for a single vent system. Any ideas?

[key]

go with one of the 2 who said it can't be done..

[cde72]

Ditto...

[kungfuparachute]

Would either of you be willing to say why? I stand to lose a bit of money over the years that I plan on staying in the home by going only 80% efficient.

[Jultzya]

Originally posted by kungfuparachute
Would either of you be willing to say why?

Please do...

[trane]

I'm going to get myself in trouble but I have to admit that I never check to see how much fall there is. If the water can drain back and not pool in the pipe there should be no reason it won't work.

[tinknocker service tech]

that would come out to 4ft to an inch. You would be ok with 2in pipe as long as it can be ran that far with the furnace you need. Three in can make it also but it wont be easy. If you start at 1/4 in per ft and go to 1/8 near the furnace chances are you will be fine but strapping will be very important so it will not sag. would strap it every three feet instead of the usal five ft. I also think it can be done as long as they do it right

[hotdog]

Take it out the roof!!

[key]

I misread your question. Give serious consideration to high efficiency and not 80%. Have your contractor map out exactly how is going to vent before you sign on the line.

[beenthere]

24' is only 6" height difference, should be able to get that with 9" joist.

Max distance is what ever the manufacturer states for that unit.

If you only get an 1/8" slope, and the condensate doesn't run back properly, you'll have alot of no heat trouble.

If 2 said they can do it, ask them if they guarranty it will work properly, if they don't, then look to the guy that already told you he can't do it.

[trane]

Sorry wrong thread

[Edited by trane on 02-01-2006 at 08:50 AM]

[t527ed]

as long as you have the pitch back to heater the pitch per foot should not be critical. it is only condensate running back to heater not turds. make sure no low spots and venting has plenty of support to prevent sagging.