A heat load calculation of my home says it requires ~36K BTU/hr of heat at a normal winter temperature (40°F), and ~52K BTU/hr at the design temperature (24°F).
An HVAC contractor has proposed installing a 95% efficiency two stage furnace that operates at either 60K BTU or 39K BTU. This makes me wonder what the optimal duty cycle is for a furnace. It seems that on a 24°F day, my furnace will be running 82% of the time. I'm unclear how a two stage furnace would split operation between high and low, so I don't know how much it would run on a 40°F outdoor temperature.
How much of an hour should be a furnace be running for optimal comfort or optimal efficiency, if they're different?