Quote:
Originally Posted by MN Renovator
Thanks for this.
I calculated as 26746 for everything above grade. Based on the heat output of my furnace and last years therms calculated into CCF using the value of heat from the gas and then calculating run time of the furnace. I'm sitting at 6.55 calculated hours of run time as a daily average for January with an 75000 btu input, 57000 btu output furnace. Either a modular furnace 45000 btu high and 30000 btu low or just a 35000 btu furnace would probably do the trick. I think 35000 btu is about as small as you can buy them.
I figure this tool is probably pretty close to matching my guess of somewhere between 30000-45000 btu from a 95+ efficiency furnace even though I have no clue what insulation is between the walls and the outside.
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Sizing a furnace for fossil fuels usually consists of doing a heating load calc like you did, and increase that by 50%, sometimes by 100% to arrive at furnace output.
Sizing a Heat Pump consists of doing a heating load calc like you did, and choosing a heat pump with a heating capacity that is slightly smaller than what is indicated. Then a back-up provision is designed in to cover the heating needs during exceptional conditions. Some of the heat pumps have built-in electrical resistance heating, some have built-in gas, natural gas or propane.
It sounds like you're really doing it right, by using a computer program and checking your results against your heating bill.
Since you have this information right at your fingertips, it would be a dandy idea to detail your work with images and all, as an example for others who may be thinking along similar lines.
Best Regards,
-AC_Hacker