Gas wall-hung boilers (also known as gas heating water heaters, see GB25034-2010 "Gas Heating Water Heaters") use natural gas, artificial gas or liquefied gas as fuel. The fuel is output through the burner and burned in the combustion chamber The heat exchanger absorbs heat, and the circulating water in the heating system is reciprocatingly heated while passing through the heat exchanger, thereby continuously outputting heat to the building and providing a heat source for the building. In addition to the heating function, the general dual-purpose gas wall-hung boiler also has the function of hot water (that is, in addition to heating, it also has the function of a gas water heater). Wall-hung boilers can provide heat sources for fins as well as for floor heating systems. Commonly used wall-hung boilers are divided into heating domestic hot water dual-use stoves and single floor heating stoves.