Useful Tips on Use of ASD/VFD for pumps

Potential Applications

ASDs are ideally suited for variable-torque loads from centrifugal pumps, fans, and blowers when the system load requirements (head, flow, or both) vary with time. Conditions that tend to make ASDs cost-effective include the following:

1. High horsepower (greater than 15 to 30 hp)—the higher the pump horsepower, the more cost-effective the ASD application.


2. Load type—Centrifugal loads with variable-torque requirements (such as centrifugal pumps or fans) have the greatest potential for energy savings. ASDs can be cost-effective on positive displacement pumps, but the savings will generally not be as great as with centrifugal loads.


3. Operating hours—In general, ASDs are cost-effective only on pumps that operate for at least 2,000 hours per year at average utility rates.


4. High utility rates—higher utility energy charges provide a more rapid payback on an investment in an ASD.


5. Availability of efficiency incentives—where they are available, electric utility incentives for reducing energy use or installing energy-saving technologies will reduce payback periods.


6. Low static head—ASDs are ideal for circulating pumping systems in which the system curve is defined by dynamic or friction head losses. They can also be effective in static-dominated systems—but only when the pump is carefully selected. A thorough understanding of pump and system interactions is critical for such applications.