I know fans are rated for positive pressure, known as hydrostatic pressure of the fan. But, are fans also rated for suction? In short, how do you know if there is enough suction to return air back to the fan?
Thanks,
- Jinx
I think your question is mistaken. The pressure quoted is differential pressure between intake and exhaust sides. How these relate to normal, ambient, atmospheric, pressure depends on the ducts. If you have no duct resistance on the intake side then the pressur there will be atmospheric while on the other side of the fan you have a higher pressure which then gradually decreasus through the ducts. I hope I am not confusing you more.
Fans are rated by a curve that shows the relationship between external static pressure (the static pressure difference between the discharge and the inlet) and flow. If the discharge is directly to the atmosphere (such as an exhaust fan), the SP at the inlet will be below the ambient pressure, and you will have “suction.”