| 摘要 |
The present invention relates to a gas boiler having a hybrid open-and-closed-type expansion tank that is controlled to adopt an open configuration when water must be added into the boiler so as to enable water to be easily added regardless of the water pressure of a tap, and adopt a closed configuration when the boiler operates after water is added so as to maintain the pressure within the expansion tank at a suitable level during switching, to thereby enable heating water to flow smoothly and the boiler to operate smoothly. For this purpose, a gas boiler of the present invention, having an expansion tank for storing circulated heating water therein and absorbing pressure changes in the heating water, comprises: a water level sensor for sensing whether or not the water level of heating water in the expansion tank lies within a set water level range; an air vent provided at one side of the expansion tank, for opening and closing an air outlet that is in communication with the atmosphere in accordance with changes in the water level in the expansion tank; and an overpressure safety valve provided at an upper portion of the expansion tank, for maintaining the pressure inside the expansion tank below a certain pressure.
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