| 摘要 |
PURPOSE:To conduct most suitable defrosting operation in accordance with the state of frost formation on an outdoor heat exchanger by providing a temperature sensor which detects temperature change in an indoor heat exchanger, a frost formation sensing circuit, and a timer circuit which changes the setting of time for defrosting operation. CONSTITUTION:The input side of a microcomputer is provided with a thermistor 7 for temperature sensing via a comparator 8 and a setting resistor 13 for a set temperature difference DELTAT. The microcomputer 9 incorporates a memory 10 which stores the temperature Ts of an indoor heat exchanger at the time of starting defrosting operation and an arithmetic unit 12 which compares a set temperature difference with the temperature difference Ts-Td which is the temperature Ts minus Td, the temperature of an indoor heat exchanger at the time when a certain time has passed after starting the defrosting operation and conducts change-over of set defrosting operation time in a timer 11. A temperature difference DELTAT between a temperature Td after a certain time N1 has elapsed and the temperature Ts is taken and it is compared with temperature T1 set beforehand. If this temperature difference DELTAT is higher than T1, a shorter defrosting time N2 is used. On the contrary if DELTAT is lower than T1, a longer defrosting time N3 is used, and it is possible to carry out defrosting operation most suitable for the state of frost formation.
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