duct size/flow

Old 12-10-14, 10:00 AM
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duct size/flow

Had a question on duct work size coming out of complete heat pump systems .
Mine has the round 2 coming out of system then about a foot and a half long ,then when it enters under home it changes over to the square style thru the rest of straight run, then the small round ones branch off to go to rooms.

If the squared duct work is 15" by15" outside measurement does that mean the duct work coming out of unit-(round foot and a half -two ft long ) has to be same on size for air flow.

I couldnt get to the round ones to measure them.
Old 12-10-14, 02:14 PM
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15x15 supply duct sized correctly would be for 1350 cfm. two 13 inch hard duct would do it. 13 inch is not common so id used 14.

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