| 摘要 |
PURPOSE:To improve safety by providing a dry burning preventing control means to turn OFF a heater if a time when a heater is turned ON by a first temperature deciding means after the heater is turned OFF by a second temperature deciding means is below a given time. CONSTITUTION:A control device 13 is provided with a first temperature deciding means 14 to compare a temperature signal from a temperature detector 12 with a first reference temperature signal and a second temperature deciding means 15 to compare a temperature with a second reference temperature signal higher than the first reference temperature signal. A dry burning preventing control means 17 to turn OFF a heater 3 if a time when the heater 3 is turned ON by the first temperature deciding means 14 after the heater 3 is turned OFF by the second temperature deciding means 15 is below a given time is provided. When a power source is turned ON in a state that a dry burning state occurs as a result of a user leaving a tank 2 in a state not to feed water therein and a heater being turned ON though there is no water, this state is detected to forcibly turn OFF the heater 3, an alarm is displayed to report it to the user and a fire can be prevented from occurring. |
