Trunk Y's vs. 90 Degree Collars

Old 12-23-08, 06:28 AM
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Trunk Y's vs. 90 Degree Collars

I planning to re-work my trunk and branch ducting.

At present, 12" round rigid trunk has 90 degree collars for the four flex duct branches to floor boots.

Would I gain air flow by changing the 90 degree collars to 45 degree Y's? So air flow would go from a 12" to 8" via 90 turn to a 12" to 8" via 45 degree turn.

Any downside to this? Does the main 12" trunk need the extra pressurization caused by the 90 degree turns to supply equal air flow to all four of the branches?

Thanks and Merry Christmas!
Old 12-23-08, 08:21 AM
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Even air flow is done with dampers. Yes you will can a small amount with 1 45% verses a 90%.

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