| 摘要 |
PURPOSE:To secure the freezing preventive effect and the reliability of the titled device by a method wherein freezing preventive and water temperature controlling thermostats are used and the operation of a cooling water circulating pump is not stopped even when the freezing preventive thermostat is operated. CONSTITUTION:The freezing preventive thermostat as a first temperature detecting element 15-a is attached to a cooling water outlet of a water side heat exchanger and the water temperature controlling thermostat as a second temperature control element 15-b is attached to a cooling water inlet of the heat exchanger. In the normal operation condition, the potentials at positive phase input terminals 15-e and 15-f of voltage comparators 15-c and 15-d are made lower than the potentials at negative phase input terminals 15-g and 15-i by so selecting the values of resistors connected to the voltage comparators. However, the above relationship between the positive input terminals and the negative input terminals of the voltage comparators is reversed when the temperature of the cooling water at the cooling water inlet and outlet of the heat exchanger reaches a set value for the prevention of freezing or the control of cooling water temperature, so that the output 15-j or 15-k of the voltage comparator 15-c or the voltage comparator 15-d goes to H-level. This H-level output is positively fed back to the input side of the voltage comparator through a feedback resistor 15-l or 15-m and such output condition of each of the voltage comparators is maintained until the temperature of the cooling water reaches a value at which the freezing preventive and the water temperature controlling operations are started again. |
