How To Figure GPM Water Flow On An Existing Chiller

Technicians calculate a chiller's volumetric flow rate similarly to how they find the flow rate in other pump systems. As with other systems, a chiller's flow rate depends on the chiller's pressure and the system's overall efficiency. This pressure is typically measured in terms of total dynamic head, a figure that considers the fluid's static pressure, the pressure the pump adds and pressure losses due to friction.

Step 1

Multiply the fluid's horsepower by 3960. If the chiller works at 25 horsepower: 25 x 3960 = 99,000.

Step 2

Multiply your answer by the pump's efficiency. If the pump works at 80 percent efficiency: 99,000 x 0.80 = 79,200.

Step 3

Divide your answer by the total dynamic head, measured in feet. If the head equals 130 feet: 79,200 / 130 = 609.2. This answer is the chiller's flow rate, measured in gallons per minute.