Linggo, Mayo 17, 2015

Heat Load Calculation

I have had several HVAC contractors quote new furnaces and ACs recently, but their heat load calculations seem to be all over the map. I also tried to ballpark it using this formula: Load (Btu / hr) = 50 x heating therms x Efficiency from a post on MichaelsEnergy.com (wasn't allowed to post link). Using that, I came up with 42,464, which is lower than any of the contractors' calculations. One told me his was 50,018 but quoted me an 80,000 BTU furnace (same size nearly every contractor has bid). When I asked him if 60,000 BTU would be sufficient, this was his response:

Quote:

"The 50k heat loss is divided by a 0.8 coefficient which pushed the input to 62,500. Thus 95% of the time a 60k would be ok but the coldest days of the year the furnace would struggle to keep up and likely lose ground."
Our home is a two-story with a basement (laundry/HVAC unfinished + finished family rm & office) near St. Paul, MN. I've had 7-8 contractors here in the last few weeks and don't feel as though I am getting any closer to a decision. Any help/advice/observations would be greatly appreciated. Thanks!

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