View Full Version : BTU and Efficiency Question
08-18-2006, 11:01 PM
I was wondering (theoretical question):
If I had a 100,000 BTU Furnace that was only 70% efficient could I replace it with a 70,000 BTU Furnace that was 100% efficient?
08-18-2006, 11:02 PM
08-18-2006, 11:14 PM
08-19-2006, 11:23 AM
08-19-2006, 02:30 PM
still some if's.
What if you only needed 55,000?
Also, you would want to consider that a 100,000 btuh furnace at 70% efficient with little off time probably runs a slightly higher efficiency. It would have a lower efficency with long off cycles.
08-19-2006, 03:21 PM
Even though the AFUE may be 70%, the actual output steady state is 80% of input. So running 24 hours a day, that sucker is putting out about 80K per hour, not 70.
Most natural draft furnaces are around 60-65% AFUE and 75% steady state output. Read the rating plate to determine what the output is, and never sized based on current equipment. (current unit could be too large)
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