Yes, I suspect this is the reason why my 2/F 1450 sqft house (with cathedral ceiling so about 1700 sqft worth of volume to cool) in a 60-70F winter climate ended up with a 100K BTU 1 stage furnace. They were spec for a possible 3.5-4 ton AC back then and the matching air handler would be for a 100K BTU furnace.Also - Here is the sequence of operations for a "multi-stage gas valve" gas furnace-
Call for heat
Fire burner 100%
Fire furnace/evap fan
Run fan/burner at 100% for a minimum TIME (5 minutes?)
If setpoint not satisfied, continue at 100% unless temperate within ____ degrees of setpoint
My problem with this is most furnace burners are grossly oversized for homes in the southeast. Firing at 100% for 5 minutes will reach the setpoint 95% of the time, resulting in the gas valve and blower speed never seeing a reduction. This means your multi-stage gas valve is never utilized.
This is my experience.....
I will never again buy a gas furnace and I'm a big fan of gas.
However, if you do not need that big of an air handler to match the AC, I think installing a smaller furnace would be the right way to go. Southeast may only need something like a 32K BTU furnace for a house my size but the AC would need to be 4 ton still, so if I were to install the same system again without going too high end like infinity / variable size unit from Lennox, I would probably just hard wire a dual stage furnace to a "low" for heating and then let the AC run like a normal dual stage AC.
Based on what you said about the Lennox earlier, I would stay away from Lennox and instead use other more stupid dual stage furnaces. Infinite "steps" heating but with a 5 min max burning before it slow down is either mal-function or poor design. Most stupid 2 stage furnaces or ACs should not be like this.
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