NATURAL CIRCULATION HEATING MULTI-PURPOSE PRESSURELESS WATER BOILER

The utility model relates to a natural circulation heating multipurpose hot water boiler without pressure, which is composed of a base, hot water tanks, a fold line type flue with a variable cross section running through the hot water tanks, an automatic water compensating apparatus, an atmospheric communicating tube, an air door controlling mechanism, an upper and a lower combustion chambers which are composed of two rectangular pyramid platforms or two circular cone platforms, a guiding priming apparatus, etc. The upper and the lower hot water tanks are interpenetrated; the flue is a structure of the variable cross section. The utility model has the advantages of high thermal efficiency, obvious coal saving, favorable natural circulation for the hot water and excellent performance for environmental protection, and the utility model is an ideal household multipurpose safe hot water boiler for heating and living.