| 摘要 |
PROBLEM TO BE SOLVED: To provide a main stop type water heater in which it is prevented from being frozen and damaged with a simplified structure even without drain operation and is again useable at all times. SOLUTION: Once ignition operation is applied to a main stop type water heater and water is supplied to a heat exchanger 1 through a water supply passage 3, a gate valve 9 opens a hot water output passage 5, and an atmosphere opening valve 8 interrupts hot water output passage 7 from the atmosphere, and further hot water heated with the heat exchanger 1 is guided to the flexible hot water output tube 5 for water output. Once the water supply is interrupted, the gate valve 9 confines the hot water in the hot water output passage 7, and the atmosphere opening valve 8 opens the hot water output passage 7 located downstream the gate valve 9 to the atmosphere, and further hot water existent downstream the gate valve 9 including the flexible hot water output tube 5 is substituted for air and is automatically drained to the outside of the apparatus. When predetermined temperature or lower is achieved, power is supplied to an electric heater 34 for heat production to insulate a water passage.
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