What must be considered for chilled water pump selection?

• A. Refrigerant type
• B. Pipe length only
• C. Motor color
• D. Flow rate and total dynamic head

Answer: (D)

In selecting a chilled water pump, the essential idea is to match what the system needs with what the pump can deliver. The two key quantities are the required flow rate and the total dynamic head the pump must overcome. The flow rate is set by the cooling load and the heat transfer requirements of the system—you need enough water flow to remove the desired amount of heat. The total dynamic head (TDH) is the sum of static head (vertical lift, if any) and all losses due to friction and fittings as water moves through pipes, valves, bends, heat exchangers, and other components. The pump must provide a head equal to TDH at the chosen flow rate, which you verify against the system curve and the pump’s performance curve. This ensures the pump operates near its best efficiency point and delivers reliable operation without over- or under-pumping.

Things like refrigerant type aren’t part of pump sizing since the pump handles water, not refrigerant. Pipe length is a factor because it contributes to friction losses, but sizing isn’t based on length alone—you must account for diameter, fittings, elevation changes, and overall system layout. Motor color has no engineering relevance to pump performance.