So the last quote added on duct work that previous quotes didn't. The questions are:
1) What would happen without upgrading the ducts.
2) Do installers reduce air flow to improve static pressures or would this damage the HX?
3) How does this affect cooling?
The idea of replacing the furnace on a 20 year old home is starting to get really expensive if I use the last quote...
Design considerations: 100K 95% VS 4TON/1600CFM (e.g., York) Michigan
A York installation manual (since I can't find a Bryant) seems to indicate that my return and supply ducts are quite undersized.
Return is 32x8 feeding into a 25x8 plenum. The manual wants 360 in^2
Supply is 24 X 8 + 2-6" rounds. This gets close to the required 280 in^2