Applications of Deep-Well Pumps

A deep-well pump is a water-lifting device in which the motor and pump are directly coupled and submerged in water; it is suitable for extracting groundwater from deep wells as well as for water-lifting projects involving rivers, reservoirs, and canals. It is primarily used for agricultural irrigation and for supplying water to humans and livestock in highland or mountainous areas, but it also serves urban, industrial, railway, mining, and construction site water supply and drainage needs. Since the motor and pump body operate while fully submerged, their safety and reliability directly impact the pump's utility and operational efficiency; consequently, high-reliability deep-well pumps are the preferred choice.

 

In groundwater-source heat pump air-conditioning systems, the water supply from a single deep-well pump is often sufficient to meet the needs of two or more heat pump units. However, actual operation reveals that while heat pump units run at partial load for the majority of the time, the deep-well pump operates continuously at full load, resulting in significantly higher electricity and water costs.

 

Variable-frequency speed control technology is widely applied to pumps and fans in air-conditioning systems due to its significant energy-saving effects and reliable control methods; the technology is also quite mature. Yet, its application to deep-well pumps in groundwater-source heat pump systems remains rare, despite being highly necessary. A survey of pilot groundwater-source heat pump projects in the Shenyang area found that, for systems with smaller heat pump capacities, the output of a single deep-well pump could satisfy the requirements of two or more units. In practice, it was observed that the heat pump units operated at partial load most of the time, whereas the deep-well pump ran continuously at full load, leading to substantial increases in electricity and water expenses. Therefore, applying variable-frequency speed control technology to deep-well pumps in groundwater-source heat pump systems offers significant potential for energy savings.

 

Deep-well pumps can utilize a temperature-difference control method. Since heat pump units operating in heating mode require the evaporator outlet water temperature to remain above a certain minimum, a temperature sensor is installed on the deep-well pump's return water pipeline, with the set temperature designated as *tjh*. When the return water temperature on the water source side exceeds the *tjh* value, the deep-well pump controller sends a signal to the variable frequency drive (VFD) to reduce the current frequency; the VFD lowers the input power frequency, causing the deep-well pump's rotational speed to decrease accordingly, along with the water supply rate, shaft power, and motor input power, thereby achieving energy savings. When the return water temperature on the water source side falls below the *tjh* value, the frequency is increased.