How would you calculate the static pressure?
How would you calculate the static pressure?
(OP)
Hello,
I want to calculate the static pressure of a zone. I know the cfm the fan is delivering, I know the motor HP. I was just wondering if there is any way to calculate the static pressure in the system based on these values or do you have to use a pitot tube or a manometer to determine that.
Also, Is there any way that you can know how much fresh air and how much return air your system is using.
Any links, papers or answers will be greatly appreciated.
Thanks
I want to calculate the static pressure of a zone. I know the cfm the fan is delivering, I know the motor HP. I was just wondering if there is any way to calculate the static pressure in the system based on these values or do you have to use a pitot tube or a manometer to determine that.
Also, Is there any way that you can know how much fresh air and how much return air your system is using.
Any links, papers or answers will be greatly appreciated.
Thanks





RE: How would you calculate the static pressure?
Regardless, with only cfm and fan HP, you can't get there.
RE: How would you calculate the static pressure?
RE: How would you calculate the static pressure?
Use equation QxT2=YxT1+(Q-Y)xT3 to determine Y.
RE: How would you calculate the static pressure?
RE: How would you calculate the static pressure?
RE: How would you calculate the static pressure?
RE: How would you calculate the static pressure?
As you can see, your question is so general that no one can figure out what you want to know because you don't know what you want to know.
RE: How would you calculate the static pressure?
Am I wrong, or is this only obvious when using a 100% makeup/outside air unit.
Mehtesham, two words "Balancing Contractor".
RE: How would you calculate the static pressure?
I would first start by finding the percentage of outdoor air, since you know the total CFM:
% outdoor air = (return air temp - mixed air temp)/(return air temp - outdoor air temp)* 100
Example: @ 2000 CFM total air...
(75 - 80)/(75-90)* 100 = 33.3% outdoor air. @ 2000 CFM x 0.33 = 660 CFM fresh air induction
As for the static pressure of the zone in question; since this is an existing system, get a manometer and static pressure probe and measure it. What you calculate may not match what's actually in the field in this case, since airflow in ducts is seldom laminar. That is why a traverse measurement is recommended.
RE: How would you calculate the static pressure?
HP = cfm x Static Pressure ( inches WG) / 6350 x Fan Efficiency??
Ive been usuing that for so long in mine ventilation , ive forgotten how it was derived
RE: How would you calculate the static pressure?