Due to the special design structure, the vacuum boiler can be used for one machine and multiple uses. At the same time, it can provide multiple hot water with different temperature difference, which can meet the needs of users' central air conditioning, heating, sanitary hot water, advanced swimming pool, hotel and other hot water supply. It can also provide process water for various industrial and mining enterprises. Due to the good heat preservation effect, the imported burner is adopted, which is suitable for the area with the altitude less than 3000m. For being heated, the heat of the burner is indirectly received through the negative pressure steam. Under the standard state, the vacuum degree in the vacuum chamber of - 76cmhg decreases with the increase of the steam pressure in the vacuum chamber; when the negative pressure steam temperature of the thermal medium reaches 94 ℃, the vacuum degree drops to - 15cmhg, at this time, the vacuum switch starts and stops the combustion operation; as the heat exchanger takes away the heat, the temperature of the thermal medium and its steam decreases, the negative pressure increases, and the vacuum is always on The switch starts the burner to cycle back and forth so as to achieve the purpose of heating water and heating. The vacuum degree of the vacuum chamber in the furnace is at least - 15cmhg and at most - 76cmhg, which always keeps the negative pressure state to ensure absolute safety. The temperature of the thermal medium and steam in the vacuum chamber can be increased to 94 ℃, so the temperature of the heating and heating water can reach more than 80 ℃. The boiler body and vacuum chamber do not bear any pressure, while the heat exchanger can bear pressure. Therefore, the whole process from commissioning to operation does not need to be checked, and no licensed boiler worker is required.