China's non-pressure hot water boiler, also known as atmospheric boiler, means that the top of the boiler does not withstand the hydrostatic pressure of the heating system. That is quite a "open hot water tank." Circulating pumps can only be installed in the hot water pipe. And to install check valve and flow control valve. So circulating water pump "does not play the role of water circulation, while the role of pressurized water, is actually a pressurized water pump." This is like the water supply pump pressurized water pump, the reservoir water out to the water tower , Then by gravity to the user. However, Japanese pressure-free boilers are not the case, it is a water-water heat exchanger installed inside the boiler, hot water heating system is not in contact with the furnace water. Circulating water pump and the role of ordinary pressure boilers, only to overcome the cycle resistance of the system without having to overcome the system of Yang Yang pressure. This is completely different from the pressureless boiler in our country. Can not vaguely say that "in recent years, 60% of Japan's hot water boilers have been replaced by pressureless boilers." So as not to be misunderstood as the promotion of pressureless boilers in Japan is Japan's kind of pressure cooker care. Advantages and disadvantages of pressureless hot water boilers 1, Advantages: According to available information summarized as follows: (1) There is no risk of explosion, may not be supervised. (2) Do not need to consider the problem of pressure relief in boiler room. (3) save steel and simplify the process. (4) scrap boiler reuse. (5) Cancel replenishment pump. (6) Power outage protection is good. (7) durable surface use. (8) to save user investment 2, disadvantages: (1) system cycle energy consumption. (2) the problem of low static pressure of circulating pump population. (3) circulating water pump inlet water temperature problem. (4) pot water and the atmosphere in direct contact with the problem. The main disadvantage of pressureless boilers is that circulating pumps have to bear the hydrostatic pressure of the system. Pressureless boilers consume about 2-7 times the pressure boilers. The higher the building, the greater the multiple.