| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an electric water heater which can boil up hot water in a hot water storage tank even when hot water is used during the waiting time to the start of electric energization. SOLUTION: This electric water heater is provided with a heater 2 for boiling up hot water by electric power, a hot water storage tank 1 for storing hot water, a cold water temperature sensor 5 for detecting the temperature of water, residual hot water sensors 71 -73 for detecting temperature according to the reside of hot water, a boil up sensor 6 to detect boiling up temperature of hot water and a controller 8. This controller 8 calculated waiting time for boiling up hot water at the end of the midnight power period on a basis of the temperature of the residual hot water and the detected residue thereof to supply a midnight power as a specified time passes. But when the water temperature sensor 5 and/or the residual hot water sensors 71 -73 detect changes in temperature during the waiting time, the midnight power is immediately supplied to the heater 2 and the supply of the midnight power is stopped as the temperature of the boil up sensor 6 reaches a specified boil up temperature.</p> |
