| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-conditioner for efficiently and positively performing defrosting even at an extremely cold region where much frost adheres to. SOLUTION: An air-conditioner 21 is composed of a compressor 22, a four- way valve 23, an outdoor heat exchanger 24, an expansion device 25, an outdoor heat exchanger 26, and a refrigerant pipe 27 for connecting them. A fresh air temperature sensor 27 and an outdoor heat exchanger temperature sensor 33 are provided near the outdoor heat exchanger 26, and a suction temperature sensor 34 is provided at the suction-side refrigerant pipe 27 of the compressor 22. When an defrosting operation for eliminating frost adhering to the outdoor heat exchanger 26 is to be made during heating operation, first, the four-way valve 23 is switched to a cooling side for performing defrosting operation in a reverse cycle system. At this time, defrosting operation time ITdef from the start of defrosting operation is counted, the four-way valve 23 is switched to a heating side when the defrosting operation time ITdef reaches preset switching time ITdef, m, and a solenoid two-way valve 30 is opened for performing defrosting operation in a bypass cycle system, thus completely eliminating frost adhering to the outdoor heat exchanger 26. |
