fan selection for duct work 1

[davidyu2404]

To select a fan with the right static pressure, should I just use the pressure loss of the critical path or add up pressure losses from all the duct sections?

 

[RandomUserName]

Critical path. All other branches will be balanced in proportion.

Do not forget to add the critical path of your return duct work, grilles, diffuses, and any other items outside the air handling unit if it is a single fan unit.

 

[willard3]

You will need to know both the static and velocity pressure in the critical path to select a fan.

 

[davidyu2404]

Hi Willard3 would you elaborate a little bit more? I have seen this equation: SP(fan)=SP(outlet)-SP(inlet)-VP(inlet). Is this what you are referring to?

 

[willard3]

Consult "General Principles Of Ventilation" in American Conference Of Governmental Industrial Hygienists "Industrial Ventilation"

There are other descriptions likely in SMACNA, this is one that comes to hand readily.