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Old 09-03-2010, 09:45 AM   #1
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how much difference does furnace size make

I have 4 different contractors and 4 different answers.

How much difference is there if I choose a 70000 btu or a 90000 btu?
I already threw out the high (100000) and the low (60000).


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Old 09-03-2010, 11:02 AM   #2
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The size should be based on a heat loss calc
Insulation, windows, your location all have an effect on sizing


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Old 09-03-2010, 07:33 PM   #3
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You can do your own load calc. well worth the 49 bucks to use it.

The 60,000 may indeed have been the right size.

An oversized furnace on undersized duct work. means higher then needed heating bills. And possible service problems, keeping it running.
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Old 09-03-2010, 08:29 PM   #4
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An oversized furnace will have chronic overheating problems/run too hot/ride the limit control and will have an expensive premature heat exchanger failure.
"Cut it twice and it is still too short".
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