| 摘要 |
PROBLEM TO BE SOLVED: To decide an empty water heater heating state without damaging a heater. SOLUTION: A deciding means 11 for test energizing a heater 32 only for a predetermined test energizing time ta is provided. The means 11 monitors a temperature rise of an outer surface near the heater 32 after the test energizing, can decide an empty water heater heating state of the heater 32, and limits the energizing time of the heater 32 only for the time ta, thereby suppressing the temperature rise of the heater 32 at the time of empty water heater heating to a small value. |
