Heating method, heating device and heating system

[0022] In order to enable those skilled in the art to better understand the solution of the application, the technical solutions in the embodiments of the application will be clearly and completely described below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only It is a part of the embodiments of this application, not all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work should fall within the protection scope of this application.

[0023] When the heat pump water heater is heated at low temperature, the high pressure that can be reached is lower. This is because at low temperatures, the compressor of the heat pump water heater cannot raise the temperature of the colder refrigerant higher than the saturation pressure corresponding to the temperature of the water tank to be heated. In this case, after the tempera