Posted 1/13/2019 13:48 (#7242412 - in reply to #7242401) Subject: RE: Any gas furnace experts
NW Indiana
It should specify 2" or 3" by the model number, doesn't matter if the outlet is 2". I know this from experience, I put in a goodman furnace in for an uncle a few years ago and made that mistake, I had to pull all the 2" and put in 3".