| 摘要 |
PURPOSE: To prevent the useless defrosting and idle defrosting at low temperature of outside air, by providing an outside heat exchanger with a temperature detector, and providing it a frosting judgment controller which receives the input of a detection signal and performs a logical operation and outputs the switching signal of a four-way valve. CONSTITUTION: A temperature detector 6 for detecting the temperature of an outdoor heat exchanger 4 is attached to the refrigerant pipe 8 on inlet side of an outdoor heat exchanger 4. The detection signal is inputted into a frosting judgment controller 7, and a judgment signal 9, which is to be outputted at judgment of the frosting, is inputted into a four-way valve 5. The logical circuit of the frosting judgment controller 7 judges the frosting when the initial value Teo reaches -20 deg.C<=Teo <=-10 deg.C and besides the differential temperatureαreaches the set value 2 deg., and outputs a defrosting start signal. Moreover, when the initial value Teo is -20 deg.C or under, it outputs a defrosting start signal regardless of the differential temperatureα. This defrosting start signal is inputted into the four-way valve 5, and the flow direction of a refrigerant is switched. Whereupon, the refrigerant compressed and heated with the compressor 3 is supplied to an outdoor heat exchanger 4, and the frost is removed by that temperature.
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