Reducing 6" ducting to 4"

PopAndSonGrows

Well-Known Member
Screenshot_20211226-204702.png
I use a 4" to exhaust a 4x4 80" high, AND teed off to a 2x2 48" high, succesfully. It does a great job but it's at 100% speed all the time.
 

mtnman2016

Well-Known Member
If a fan tries to push 6" of airflow through a 4" reducer it will and I must exemplify the word will, reduce the life of the fan. It is proper physics. However, does a 6" fan really push the CFM to overfill a 4"? That can be debated.
 

Boatguy

Well-Known Member
If a fan tries to push 6" of airflow through a 4" reducer it will and I must exemplify the word will, reduce the life of the fan. It is proper physics. However, does a 6" fan really push the CFM to overfill a 4"? That can be debated.
Mine is dummed down to a 4" dryer vent.
It still works fine. 90's and other bends can be more restrictive than shrinking diameter, smooth wall tubing is best.
 
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