I'm replacing an old 1966 200,000 Btu input furnace with a 95% efficient furnace to get the tax credit. So far I have one estimate and it has generated a few questions. The dealer is recommending a 90,000 Btu output Amana AMH95 two stage burner with multispeed blower.
1) I did a manual J calculation and also back calculated heat loss based on 2008 gas consumption, 60% efficiency and 2008 Heating Degree Days for my area (SE Michigan). Answer was 32,000 Btu / hour heat loss. Assuming this calculation is correct, how big should I go on the furnace? Dealer says he only uses house square footage to size the furnace, independent of insulation, air infiltration etc. He also said that since it is a two stage, normal sizing rules don't apply.
2) Since the basement ceiling is drywalled, it would be a bear to rewire the thermostat, so I think I'm stuck with a single stage thermostat. The dealer quote says I can have any brand of furnace I want for the same price with the same basic specifications (95%, two stage burner, multispeed). Does being stuck with a one stage thermostat limit my choices of other equivalent furnaces?
Thanks in advance for your advice and feedback.