PURPOSE: To reduce the range of hunting by a method wherein a thermosensor and an auxiliary thermosensor are provided on the side of the outlet and on the downstream side, respectively, of a heat exchanger and the delay of response time of the thermosensor is corrected by utilizing the phase difference in temperature due to distance so that when the temperature detected by the auxiliary sensor rises high, a set temperature is shifted to a high temperature side.
CONSTITUTION: The thermosensor 11 is provided between the outlet port of the heat exchanger 2 and the inlet port of a mixing tank 4 and the auxiliary thermosensor 12 is provided on the outlet port of the mixing tank 4. When the temperature of the thermosensor 11 rises, the resistance value of the sensor decreases and therefore, the voltage impressed upon an inertible input terminal (-) drops. Thus, when the voltage drops lower than a reference voltage at a non-invertible input terminal (+), the output terminal of a comparator 14 goes to Hi level to thereby stop the combustion of the hot water feeder. Further, since the thermosensor 11 and the auxiliary sensor 12 are connected in series with each other, the voltage to be impressed upon the invertible input terminal is determined by both of the temperatures detected by the thermosensors. On the other hand, when the temperature of the auxiliary thermosensor 12 rises, the voltage impressed upon the invertible input terminal increases and therefore, the set temperature for starting and stopping the combustion of the hot water feeder rises. Accordingly, the value of the set temperature for stopping the combustion is controlled to a low level while the value thereof for starting the combustion increases and as a result, the range of hunting is reduced.
ISHIYAMA MASAAKI
KODAMA YOSHIHIRO
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