What effect?

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Old 07-19-10, 08:06 AM
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What effect?

I am installing 8" ducting thu-out and would like to reduce to
6" at the registers, what effect will it have on volume and cfm? This is for heat only and I am maxed out on number of registers and am borderline on recommended cfm.
 
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Old 07-19-10, 07:26 PM
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Arrow Register's 'Ak' is in sq.ft., times the measured velocity in FPM = CFM

Originally Posted by randm View Post
1) I am installing 8" ducting thu-out and would like to reduce to 6" at the registers, what effect will it have on volume and cfm?

2) This is for heat only and I am maxed out on number of registers and am borderline on recommended cfm.
1) You need to perform a Manual D to know how the air handler & duct system will function.

The reducer from 8" to 6" will increase the velocity with a small loss in delivered CFM.

Then you will need to select diffusers that will have the desired velocity, throw & delivered CFM.

Search Hart&Cooley & Lima for register info., the 'Ak' is the free air area of the register in sq.ft., times the "measured velocity" in FPM = CFM.
 
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