Originally Posted by
udarrell
I live in SW WI & have a 57,500-Btuh propane furnace; with the temp at around 12-F & wind chill at -3-F it only takes 16,292-Btu during with one houir & 7 minutes off.
I use a SWING temp room- thermostat set at a 7-setting for over a 3 close to 4-F swing.
Runtime was 17-minutes at 958.333-Btu/per minute, or 16,292-Btu.
It would take high winds at deep sub-zero temps to get to the 57,500-Btuh capacity of the furnace; if it ever does!
Of course, it's a 95% with outdoor combustion air intake; the much colder weather combustion air temp drops the fire chamber's temps as it dilutes it; similar to pouring real cold cream into a boiling hot cup of coffee.
Winter design at La Crosse WI at 99% is -13-F; at 97.3% it's -9.
Madison WI is the same distance north; 99% is -11-F; 97.5% is -7-F.
It will be cruising at those temps because, I've checked it below zero, - but can't find those results to publish.
For those rare periods when it's extremely cold you could have a portable electric heater to supplement the furnace for those short periods of time; ... if ever needed.
I couldn't see the square footage of your home? Mine is a 2-story with a deep basement & heating around only 1000-sf.