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Old 01-10-2010, 09:48 PM   #1
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Return Air Size


I am finishing my basement and want to make sure my return air is done right.

I have put in 5 6" duct extensions.

I know that what I put out has to equal what I pull back.

So the cross sectional area of these five new ducts is 140.

So the questions I have are really about how many wall cavities I need. I have been wondering if I need 3: 3 wall cavities each with a cross sectional area of 3.5 * 16 for a total of around 160.

Also for the ducts that connect to the wall cavities to the existing cold air return square duct work, I am not exactly sure how many I need.

Thanks for any help and input.
b

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Old 01-11-2010, 06:10 AM   #2
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Return Air Size


Probably 3-8" or 4-7"

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Old 01-11-2010, 04:40 PM   #3
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Return Air Size


Quote:
Originally Posted by beenthere View Post
Probably 3-8" or 4-7"
Thanks.

So a wall cavity for each of these also?
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Old 01-11-2010, 04:52 PM   #4
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Return Air Size


A 2X4 cavity, will only pull about 140CFM.

So add up what your supply CFM is. And use as many cavities as you need to equal that. And a cavity should have its own individual duct back to the trunk.
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