Tech Questions About New Gas Furnace

[chicagoglenn]

I am looking at new high efficiency gas furnaces. Our townhome is 2200 sq ft with 3 floors (basement, first and second). What is the advantage to a 2-stage furnace? I've also been told by a contractor that some high efficiencies require a 3" pvc exhaust. We will be replacing a 90% efficient (22 yrs old) furnace that has a 2" pvc exhaust running approx. 20' to outside wall. Do higher efficient furnaces require a 3" exhaust? Is there a simple way to figure the size furnace you need? We are in the Chicago area, house is fairly well insulated, and we are a center unit with only a few windows. Any suggestions for type of furnace, i.e. 2-stage or other.
Thanks,
Glenn

[BaldLoonie]

No simple way to determine size. A good dealer will do a heat loss calc and size accordingly. The rest will replace with what you have even though it is likely oversized. Condos seem to be the worst at oversizing, especially those that base on sq ft and don't consider common walls.

Yes, many furnaces today require 3" pipe even though the old one was 2". Another way that downsizing if possible could help.

2 stage furnaces have a lower fire 1st stage for longer, more gentle burn cycles in mild weather. Strictly for comfort but customers really seem to like them.

[tinner73]

Glenn..email me. i'm local. click on my profile.