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Old 06-27-2011, 02:20 PM   #1
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how to size furnace- another


replacing a 30 yr old carrier gas hot air furnace, 75K, output is 60K. 12- 5" ducts, supply is 13x19 and return is 8 x 24, interior 3 level townhouse 900 sq ft total. My heat-loss is approx 50K, i picked a comfort-maker, 66K, output is 53K- i can't figure on CFM? 720 or 1195? for heat only- later i may- though slim possibility, will connect an a/c- 2 years.
thanks, Jack, newbie.

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Old 06-27-2011, 06:34 PM   #2
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how to size furnace- another


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Originally Posted by jackofall2 View Post
replacing a 30 yr old carrier gas hot air furnace, 75K, output is 60K. 12- 5" ducts, supply is 13x19 and return is 8 x 24, interior 3 level townhouse 900 sq ft total. My heat-loss is approx 50K, i picked a comfort-maker, 66K, output is 53K- i can't figure on CFM? 720good for a 2 ton AC or 1195good for a 3 ton AC? for heat only- later i may- though slim possibility, will connect an a/c- 2 years. Cannot upsize the fan/cfm later so if you may need 3 tons of cooling you better order that one now.
thanks, Jack, newbie.

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Old 06-28-2011, 04:31 AM   #3
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how to size furnace- another


Your 12-5" ducts are only good for roughly 720 CFM.
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