Restrictions in return duct?

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Originally posted by dash

So we need 229 cfm per space for 1600 cfm,which would be a Friction Rate of .15 per hundred

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I agree with what your saying here but was just wondering why you use .15 per 100FT? Is that due to the wall material?

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Originally posted by pm4589

Quote:

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Originally posted by dash

So we need 229 cfm per space for 1600 cfm,which would be a Friction Rate of .15 per hundred

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I agree with what your saying here but was just wondering why you use .15 per 100FT? Is that due to the wall material?

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Using the ductolator to determine FR,14"X3.5",wall space,looking at it as a 14X3.5 duct,if we had 229 cfm,it would be .15 FR per 100' of duct.

Since the original poster has stated they are high wall returns,then 10 ft of wall space/duct,would be .015 Friction Rate.

Right after I posted I figured it out.....
Couldn't delete in time.

So were looking at about 620 CFM @ 700FPM

[Edited by pm4589 on 03-04-2005 at 02:46 PM]

Quote:

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Originally posted by pm4589
Right after I posted I figured it out.....
Couldn't delete in time.

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No problem,since you understand ,please post on this site more often,we can all use the expertise.