| 摘要 |
PROBLEM TO BE SOLVED: To reliably open and close an automatic air vent device for releasing air retained in a pipe of a hot water heater without causing chattering, and make the air vent device function as a pressure relieving device. SOLUTION: A solenoid ON-OFF valve 6 is mounted on the top end of an air separating cylinder 2 of the automatic air vent device 1. A water fill-up electrode 7 and an idle heating avoiding electrode 8 are installed on the upper part and the lower part of the side part of the cylinder 2. A pressure sensor 13 is installed above the electrode 7. When the water level is lowered below the electrode 8 due to increase of air quantity in the cylinder 2, the valve 6 is opened to release air. When the water level is raised above the electrode 7, the valve 6 is closed. When pressure in the cylinder 2 reaches a limit pressure or higher, the valve 6 is opened irrespective of the water level by a signal from the pressure sensor 13.
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