The whole system of air energy water heater is composed of heat pump host, water tank, solenoid valve, circulating pump and pipeline. The water tank of household machine can be divided into water circulation type, external coil type and internal coil type according to the heat transfer structure. There are also direct heated commercial engines. Whether they are direct heated or circular, their working principles are almost the same.

The water circulating heating in the household appliance is fast, safe, and has a long service life. There is no distance limit between the host and the water tank, but the production cost is relatively high, and the efficiency is very low. The most vulnerable thing is the circulating pump, which increases the power consumption, which is contrary to energy conservation. At the same time, circulating heating in the process of using water will lead to serious water mixing, and the heat source is also unstable. The external coil type has a long life and good safety performance, but the heating is slow and the waiting time is relatively long. Built in coil type heating is fast and efficient, but due to the influence of water quality, pipe material and thickness, there will be hidden dangers of coil corrosion and leakage after long-term use.