What is a Fan Curve?
It is a characteristics curve, which shows the relationship between static pressure and the air flow rate of the fan. The fan manufacturers perform actual test to find out the static pressure value of the fan for the different air flow rates to plot the fan curve.
Please note from the fan curve that, as the flow rate increases the static pressure decreases, means at higher flow rate the fan will be able to withstand lower system resistance (or back pressure).
How to Select a Fan
- After you posses the fan curve from the supplier, you have to know or create one more curve that is system curve.
- The intersection point of the fan curve and the system curve will give you the operating point of the fan or you can tell your fan supplier what is the static pressure and flow rate you are looking for.
- The fan supplier will then select a suitable sized motor to the fan.
The article has explained the fan curves basics, but drawing correct system curve is not a easy task and selecting the fan’s operating point depends largely on preparing correct system curve. I will write something next on how to draw a system curve.