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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 crucial factor for user health. Additionally, the quality of tap water in China, especially when using circulating water pumps, plays a vital role and cannot be overlooked. Therefore, not every shielded pump available on the market is suitable for use as a circulating pump in heat pump water heaters.
From a health perspective, according to the Chinese 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 standards, all pipelines and heat exchange equipment on the heat source side must have anti-corrosion properties. The heat pump water heater should not contaminate the water it uses. As an essential component on the hot water side, the pump must be free from any potential sources of secondary pollution.
Another major concern is scaling. Tap water in most parts 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 in water pumps and piping systems. Since shielded pumps rely on the transported medium for lubrication of the shaft and bearings, scaling is almost inevitable. In prolonged periods of inactivity, water can remain inside the pump, leading to blockage of the shaft and bearings. This can result in the pump failing to start when the heat pump water heater is turned on, causing the compressor’s temperature to rise excessively and triggering the protector to trip repeatedly.
Energy efficiency is also a key consideration. According to the national standard "Household and Similar Purpose Heat Pump Water Heater," the actual power consumption of the pump must be included in the energy efficiency calculation. Furthermore, circulating heat pump water heaters are required to meet an energy efficiency rating above 3.6, which is higher than the 3.4 requirement for static models. This makes the energy consumption of the pump even more critical, as it directly impacts the overall efficiency and performance of the system.