Existing 80% staying, replacing gravity w/ 90% venting question - Contractor Talk - Professional Construction and Remodeling Forum

02-10-2004, 01:37 PM

I am buying a house that's been split into two apartments. One apartment has a new 80% furnace. The second apartment has an old gravity furnace that I am replacing with a 90% furnace. Both of the existing furnaces vent into the masonry chimney. I don't think that there is a condensation problem now since the gravity exhaust is so warm. However, when I install the 90% furnace, what is my best venting solution? Stainless Steel flue liner? Or can the 80% and 90% both go out a PVC vent?

Bjd · 02-11-2004, 06:15 AM

90+ is a seprate flue to the outside, do not connect to the flue.
Leave the 80% where it is just block off the old opening where the old unit connected.

Benie

02-17-2004, 08:46 AM

Quote:

Originally Posted by Bjd

90+ is a seprate flue to the outside, do not connect to the flue.
Leave the 80% where it is just block off the old opening where the old unit connected.

Benie

Thanks Benie. Also, do 80% furnace exhausts need a flue liner in an old chimney?

Bjd · 02-18-2004, 05:45 AM

Is the flue on the inside of the home? if so no liner is needed.
However if the flue is on the outside of the home, you may need a liner as the flue will not be heated by the old unit.

Bernie