PURPOSE: To prevent the scalding due to unexpected delivery of high temperature water from developing by a constitution wherein the hot water supply is stopped by closing a motor driven valve, when hot water temperature becomes higher beyond the set range of service hot water temperature, and the motor driven valve is opened only for a certain period of time by operating a manual switch equipped on a hot water supplier.

CONSTITUTION: When hot water temperature becomes higher beyond the range of service hot water temperature, a comparator circuit 18 releases the drive of a relay 19, resulting in changing-over a contact 24 to a normally closed contact in order to actuate a motor valve 11 until the state to close a hot water supplying piping 8 is realized and then stopped. At this time, at the same time, an alarm is generated by an abnormal temperature alarming part 25. In order to make the spontaneous hot water supply possible, a switch 21 to release the motor valve 11 is equipped. When the switch 21 is closed, a timer circuit 20 is put into actuation so as to drive the relay 19 for a certain period of time in order to make hot water supply possible. After the predetermined time, the drive of the relay 19 is released, resulting in closing the hot water supplying piping.