| 摘要 |
PROBLEM TO BE SOLVED: To prevent possible erroneous recognition of the opening or closing state of a door, caused by the lowered insulating performance of a electric heater. SOLUTION: There are arranged an electric heater 9 earthed for raising the temperature of water in a water storage tank, a connection circuit 28 in which a first series circuit portion 46 comprising a power source 50 with one side thereof earthed and a door switch 22 and a second series circuit portion 47 comprising a current actuation element 51, the electric heater 9 and a heater switch 57 are connected in parallel and a heater control means 54 recognizes the opening or closing state of a door from the presence of the operation of the current actuation element 51 to cut the energization of the electric heater 9 by opening the heater switch 57, an isolating switch 57 adapted to be opened when at least the door switch 22 is opened is inserted and connected between the second series circuit portion 47 and a terminal (c) connected to the side of the door switch 22 of the first series circuit portion 46 out of two terminals, i.e., one of the second series circuit portion 47 and the other of the current actuation element 51.
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