Is my existing ducting undersized?

Old 08-27-15, 10:53 AM
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Is my existing ducting undersized?

I have the ceiling down in my kitchen (the closest room to the utility closet where the furnace is). I have a 2 ton Bryant 925t furnace, which according to this page (Gas Furnaces Matrix) puts out between 1000 and 2200 cfm. On both the supply side and return side I have 14x8 sheet metal ducts. The supply side eventually goes down to 8x12 after 15 feet or so and then down to 8x10 further on. From what I understand, 14x8 can carry 500 cfm ( Should I replace the 14x8 while the ceiling is down and if I only do that section (and not after it goes down to 12x8, etc) will that really make any difference?

Thank you for any advice
Old 08-28-15, 04:19 AM
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14x8 is good for 550cfm supply 450 cfm return
Old 08-29-15, 12:07 AM
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To give a more direct answer, yes, your ductwork on both the supply and the return is woefully inadequate.

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