We all know that lot of energy is wasted in fan/pump/blower applications if proper designing is not done .When we use conventional motor control system, in which AC motor is run at full speed, the flow of gases/air /liquid is regulated using the damper /throttle control. In this process , substantial energy is lost in the damper / throttle. This waste of energy can be as high as 25 to 30 % of motor rating.

Always go for reliable v/f , variable speed drives to control the speed of fan/pump/blower, which in turn will automatically control the flow. Hence you can eliminate the need of damper/throttle. Your pay back period can be even less than one year.