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Old 11-01-2005, 07:44 AM
Jim H Jim H is offline
Join Date: Aug 2000
Location: Holland, MI
Posts: 1,316
Originally Posted by Brian Carlton
I'm curious to know if you have ever had a 100,000 BTU furnace running flat out in MI?
No, that's never happened, even on the coldest days. It's working hard when it on 10 minutes, and off 20 minutes, or 33% duty cycle.

I don't think any HVAC contractor wants to risk that a furnace will fall 10% 'short' on the coldest days, so they upsize the rating.

That, or running the blower fan 24/7 would burn it out.

I would think that a 50,000 BTU unit, with a 2-speed fan, low for heating, high for cooling, would be a bit more efficient, since you would not have the losses of the heat up/cool down portion.
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