A water source heat pump is a water heater that USES the energy in the water to generate heat energy. This heat is converted to indoor hot water and heating, which can provide different hot water needs for the family 24 hours a day and at the same time use the least amount of energy to meet the water demand. The water source heat pump works in accordance with the principle of \"reverse Carnot\". The principle of reverse Carnot cycle is that the liquid refrigerant of low temperature and high pressure is changed into the liquid refrigerant of low temperature and low pressure after being throttled by the expansion mechanism, and then enters the water exchange system to absorb the heat of water through evaporation for heat exchange.