Flex Duct Connector Pressure Drop Coefficient

[rudytuesday]

Hi! I'm looking for a rule-of-thumb fitting loss coefficient (C) for a flexible duct connector. I've looked through SMACNA and ASHRAE and haven't been able to put my finger on a coefficient. Does anyone have a reference where a coefficient can be found? Thanks!

 

[marcoh]

Depends on how well it is installed!

If the flex connection is installed nice and straight (as it should be) the pressure loss will be negligible.

If the flex connection is used to take up misalignment between the connecting pieces, who knows?

 

[BronYrAur]

ACCA has a residential duct sizing book that lists flex pressure drop, but marcoh is absolutely correctly. The actual loss could be substantially higher than the published data if the installation is poor.

 

[trashcanman]

Flex duct pressure drop is approx. 2 x sheet metal ductwork.