High-head pump for chillers/chiller units cannot be used for low-head applications.

Many users believe that selecting a pump with a higher head capacity before purchasing a chilled water unit or a chilled water package will allow for a broader range of head operation. This misleading misconception leads to the selection of a pump with an excessively high head capacity for chilled water units or packages. In reality, for centrifugal pumps in chilled water units or packages, once the pump model is determined, its power consumption is directly proportional to the actual pump size and flow rate. When the pump operates at a lower head, the flow rate increases; this results in higher current, while a lower flow rate corresponds to lower power consumption. Conversely, reducing the head increases the flow rate and the power consumption. Therefore, to prevent motor overload, it is generally required that the pump's actual head not be less than 60% of its rated head. Consequently, when a chilled water unit or package's high-head pump is used for low-head applications, it is prone to motor overload and overheating, which can lead to motor damage. If emergency use is necessary, the outlet flow must be regulated using the outlet valve installed on the discharge pipe, typically with an automatic regulating valve (or wooden blocks, and other methods) to reduce the outlet flow and prevent motor overload. Monitor the motor temperature, and if it overheats, reduce the outlet flow or shut down the motor promptly to avoid motor damage. Some users force a reduction in flow by lowering the power supply voltage, which increases the motor load. In fact, the opposite is true; all centrifugal pump discharge stations of chilled water units or packages are equipped with valves to reduce motor load. Before shutting down the pump, the valves should be closed, and after starting the pump, they should be gradually opened to prevent excessive current at startup.

The pressure of the串联水泵is cumulative.

Proper installation should be as follows: Install the low-head pump in front of the high-head pump, ensuring that the outlet of the low-head pump feeds into the inlet of the high-head pump. A challenge here is that the outlet pressure of the low-head pump must not exceed the maximum inlet pressure of the high-head pump; otherwise, overflow and leakage due to overpressure may occur.