| 摘要 |
PURPOSE:To prevent a boiler from freezing, by operating circulation pump only when a water temperature is lower than about 4 deg.C. CONSTITUTION:As for a controller 12 which controls a burner motor 2 and a circulation pump 5, a relay switch 15 is changed over to a contact point b when a water temperature of about 4 deg.C is detected by a water temperature detecting thermistor 6, only the circulation pump 5 is operated, and the relay switch 15 is changed over to a contact point a. The burner motor 2 is controlled by both an operation switch 13 and a relay switch 14 which is opened when the water temperature of about 80 deg.C is detected by the thermistor 6. |
