Fan static pressure

[mrashidmk]

how can i calculate the total pressure drop if i know the fan static pressure and external static pressure?
fan static pressure = 2877 Pa Suc = -533 Dis = 784
external static pressure = 1063 Pa suc = -312 Dis = 401

 

[willard3]

Total pressure = static pressure + velocity pressure

 

[Drazen]

why would you total it? fan s.p. need to be matched with ducting s.p., not totaled with it.

 

[ME27272727]

You are missing the velocity pressure component. The static pressures you listed were given at a certain cfm. Use that data to calculate velocity pressure.

 

[junagco]

If you are referring for the air handling unit (AHU), then the total pressure drop is the one also called total static pressure (TSP).

TSP = ISP + ESP​

where: ISP or internal static pressure - summation of pressure drops caused by mixing box, filters, and coils.​

ESP or external static pressure - summation of pressure drops caused by external supply/return ductworks.​

No problem for ESP as this is already given, 1063 Pa.
What confusing is the given fan static pressure, 2877 Pa. What type is this pressure, TSP or ISP. So where did you get this pressure? If this obtained from fan manufacturer catalog, then this is the pressure capacity of fan that will cover both the ISP and ESP of the air distribution system.

So say this fan static pressure is the fan or blower capacity thus we can consider this as our TSP.​

Hence we can calculate the ISP (2877-1063) which will be 1814 Pa.​

So this means that the accumulated pressure drop by AHU's mixing box, filters, and coils should not exceed 1814 Pa.​

I hope my answer is acceptable.

HVAC Zone

 

[ME27272727]

Are you referring to "Total Pressure" or "Total Static Pressure"?


Total Static Pressure = Internal Static Pressure (filters, coils, etc.) + External Static Pressure (ductwork, air terminals etc.)

Total Pressure = Total Static Pressure + Velocity Pressure

Typically, fans are selected based on an external static pressure with a corresponding CFM. From there, the manufacturer will add in their internal static pressure losses, and then be able to calculate a total pressure and select the correct fan for the application.

 

[mrashidmk]

Thanks for the answers.. Expecting more help in the future