Heat pump is an energy-saving device that uses high-level energy to make heat flow from low-level heat source to high-level heat source.  As the low-level heat source of the heat pump, air is inexhaustible, available everywhere and can be obtained free of charge. Moreover, the installation and use of the air source heat pump are relatively convenient.
 Classification of Air Source Heat Pumps 
According to the unit capacity, it is divided into: household small unit, medium unit, large unit, etc.
According to the unit combination form, it is divided into: integral unit (unit with one or several compressors sharing one water-side heat exchanger is called integral unit) and modular unit (unit with several independent modules is called modular unit).

 Characteristics of Air Source Heat Pump 
(1) The air source heat pump system integrates cold and heat sources, does not need to set up a special refrigerating machine room and boiler room, the unit can be placed on the roof or the ground at will, does not occupy the effective use area of the building, and is very simple to construct and install.
(2) Air source heat pump system has no cooling water system, no cooling water consumption and no power consumption of cooling water system.  In addition, many cases of Legionella infection caused by cooling water pollution have been reported. Considering air source heat pump has obvious advantages from the perspective of safety and hygiene.
(3) The air source heat pump system is safe and reliable, and has no pollution to the environment because it does not need a boiler, a corresponding boiler fuel supply system, a dust removal system and a flue gas discharge system.
(4) The air source heat pump cold (hot) water unit adopts modular design, no need to set up a standby unit, and the computer automatically controls the operation process to adjust the operation state of the unit so as to adapt the output power to the working environment.
(5) The performance of air source heat pump will change with outdoor climate change.
(6) In places with low outdoor air temperature in northern China, auxiliary heaters are required due to insufficient heat supply from heat pumps in winter.