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Circulating pump requirements for heat pump water heaters
At present, the hot water generated by domestic heat pump water heaters is directly used as tap water, making its quality a critical factor in user health. Therefore, ensuring that the hot water remains free from contamination is essential. Additionally, when selecting circulating water pumps, the quality of tap water in China must be taken into serious consideration, as it significantly affects system performance and longevity. Not all shielded pumps available on the market are suitable for use in heat pump water heater systems.
Health standards play a vital role in this context. According to the national standard GB/T 23137-2008 "Household and Similar Purpose Heat Pump Water Heater," section 5.1.2 states that, under the condition that the inlet water meets national requirements, all pipelines and heat exchange equipment on the heat source side must have anti-corrosion properties. Moreover, the heat pump water heater should not contaminate the water during operation. As an essential component of the hot water piping system, the pump must not become a source of secondary pollution.
Another significant issue is scaling. Tap water in most regions of China is classified as hard water, containing ions such as Ca²âº, HCO₃â», Fe²âº, Mg²âº, and Cr³âº. Over time, these minerals can lead to scale buildup inside the pump and piping system. Since shielded pumps rely on the transported medium for lubrication of the shaft and bearings, scaling is an unavoidable problem. In particular, if the pump remains idle for extended periods, water can stagnate inside, leading to blockage of the shaft and bearings. This can result in the pump failing to start when the heat pump is activated, causing the compressor’s temperature to rise excessively and triggering the protector to trip repeatedly.
Energy efficiency is another crucial aspect. According to the national standard "Household and Similar Purpose Heat Pump Water Heater," the actual power consumption of the circulating pump must be included when calculating the energy efficiency of the system. Furthermore, the energy efficiency requirement for circulating heat pump water heaters is above 3.6, which is higher than the 3.4 threshold for static models. Therefore, minimizing the pump's energy consumption is even more important in these systems to ensure overall efficiency and compliance with regulations.