| 摘要 |
PROBLEM TO BE SOLVED: To secure safety and to establish redundancy and fail safe in a safety circuit for shutting a gas passage of a hot-water supply / heating machine. SOLUTION: Gas valves 1 and 2 are usually controlled by control from a microcomputer 13. When the microcomputer 13 fails, however, if a non-burning of a burner 3 occurs in a state of the gas valves 1 and 2 being opened, an abnormal detection signal is outputted from a monitor circuit 17 regardless the control of the microcomputer 13 to turn off power supply of the gas valves and to close the gas valves 1 and 2. Thus, even when the microcomputer 13 fails, the gas passage is shut to secure the safety. COPYRIGHT: (C)2004,JPO
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