Compressor of Air Source Heat Pumps vs. Compressor of Air Conditioners

With the development of the market of air to water heat pumps (heat pump water heaters), the mode of using the structure design of air conditioners adopted before has been changed. Many compressor manufacturers have invested in the development of special compressors for heat pumps in order to provide essential guarantee for the healthy development of heat pump water heaters (HPWH). The operation principle of HPWH is quite different from that of air conditioners, which determines the differences in design concepts between heat pump compressors and AC compressors.

In addition, air conditioners are mainly used for cooling in summer, so AC compressors were applied in air source water heaters at the beginning. The temperature in the south is generally above 0 ℃. Therefore, these compressors can also support the operation of the water heaters. However, with the popularity of air source heat pump water heaters in colder areas, as well as the rise of house heating & cooling needs, AC compressors gradually can not meet the market demand. Therefore, air to water heat pump should be equipped with a heat pump compressor instead of an AC compressor, the reasons of which will be listed as follows.

1.         Air conditioners are mainly used in summer. Water heaters belong to a type of daily necessities needed all the year round, and the operation time in winter is particularly long. The time needed to heat a tank of water in winter is several times as long as that in summer. Therefore, two thirds of the life of a heat pump water heater is consumed in winter.

2.         The outlet water temperature of the air source heat pump is above 55℃, and the water tank temperature will drop gradually when it is being used. When it drops to about 45℃, the compressor needs to start running, so it is basically operating in the area with high condensation temperature. The condensation temperature is the main factor affecting the life of the compressor. Under the same operation time, the comprehensive load of the compressor in the heat pump water heater is much higher than that of the compressor in the air conditioner.

3.         If the air water heat pump is used for house heating + domestic hot water, it will run for a long time in winter, especially in the cold climate. The compressor can operate in -25℃ ultra-low temperature environment, and the low-temperature heating capacity can be increased by 100%. In contrast, the performance of the AC compressor begins to decline below 0℃. To a certain extent, although it can still be started, the defrosting time is very long. The performance is not efficient even when it is turned on, which consumes a lot of electricity. In some southern areas, the winter is short. Some people will buy AC for house heating, but the heat distributed is not comfortable, and what's more, the power consumption is high.

4.         The main driving force for consumers to buy air source heat pump water heaters is energy saving, comfortable and convenient with a large amount of hot water. The ASHP is able to supply 24-hour constant temperature hot water. They can use hot water for bathing, washing vegetables, washing dishes and washing clothes. In winter when the water temperature is too low, more hot water is used, which also increases the working time of the unit.

Based on the above factors, it can be seen that the actual operation time of air source heat pump water heaters will be greatly increased. In order to ensure that there is less failure in the life cycle with stable operation and strong heating efficiency, the compressor needs to be able to withstand 20000 hours of actual operation, which the AC compressor can not load at all. Therefore, it is very necessary to use heat pump compressors for air to water heat pumps.