How heat pump water heater works in heating?

Systems of heat pump water heater works in sanitary hot water heating:



  1. Compressed by compressor, low pressure and low temperature refrigerant turns into high pressure and high temperature, and passes through reverse valve to condenser (Water Heat Exchanger); heat energy transferred to water and refrigerant turns into high pressure and low temperature liquid; and water was heated.
  2. Then refrigerant throttled by expansion valve and becomes bigger in size, changed to low temperature and low pressure refrigerant in partial liquid and partial gas status.
  3. Then liquid gas mixed refrigerant goes into evaporator Air Heat Exchanger); fan system blows air through the fin-tube air heat exchanger so that refrigerant will absorb heat from surrounding air and turn into gas status.
  4. Eventually, the refrigerant passes through reverse valve and goes into compressor and repeats the cycle.       


  1. When system operates in heating mode in condition of cold weather, frost will be possibly formed on the surface of evaporator (Fin-tube Air Heat Exchanger) and reduce the heat absorption.
  2. Activation of defrost will depends on temperature and operating time.
  3. If defrost program activated, system will reverse to cooling, so that the frost on fin-tube air heat exchanger will be melted. During this process, fan does not rotate when system defrosting.
  4. When defrost program stop, system will switch back to heating.