Flex Duct Pressure Losses

[Webber]

Does anyone know of a good site calculator to determine static pressure losses in flexible duct?

 

[RichAC]

I don't know if you still require this, but here are two links that may help

http://www.casco-flex.com/Commercial/ProductCascoflexClass1ULListed.htm

http://www.hartandcooley.com/flex/air_friction_chart.pdf

For low pressure duct systems such as a small 5 ton or less, ACCA recommends that the velocity not exceed 600 FPM.

 

[chicopee]

Here is a good rule of thumb: use straight piping charts Delta P vs. flow rate and double the Delta P (pressure loss) for the same flow rate. You will be on target but if you have any doubt check with flex ducts manufacturers as they all provide these charts free of charge right on line.