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Old 01-09-2010, 10:08 AM   #1
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Replacing Square ductwork with Rectangular

Hi, I'm starting a basement remodel and I'm trying to figure out what to do with the ductwork.

It's a simple system, two main ducts coming off the unit and going across the middle of the room through 10 inch square metal ducts before heading upstairs.

The problem is that my ceiling is only about 7 feet high and these suckers come down 12 inches and cause us to duck when walking through. So, I'm wondering if I can simply replace the square ducts with rectangular ducts that might buy me a few more inches of head room. Shouldn't this be simple? I'm thinking that as long as I end up with the same cubic inches of airspace in the duct, I can change the shape, right?


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Old 01-09-2010, 10:46 AM   #2
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Yes you can. Don't get the ratio past 3:1 or the air flow will be hampered.


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Old 01-09-2010, 12:33 PM   #3
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Wading through this link may prove fruitful
You don't want to be adding duct fans and other bandaids to your work, after your install.

ASHRAE literature is costly and hard to come by, but this book
might be available in your local library. It has chapters on HVAC stuff.

You might also want to research 'register throw'.

Boning up on thermodynamics prevents gross errors.
Everyone makes minor errors.

Last edited by Yoyizit; 01-09-2010 at 12:39 PM.
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Old 01-09-2010, 01:28 PM   #4
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You can use 8X14, or 6X18(8X14 is better).
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basement , duct , ductwork , hvac , remodel

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