| 摘要 |
PROBLEM TO BE SOLVED: To reduce switching loss from a forward cycle defrost to a reverse cycle defrost by conducting a reverse defrost operation for a predetermined time when a detected temperature exceeds a predetermined threshold value at the time of forward cycle defrost operation, and then closing a switching valve in a bypass circuit. SOLUTION: When a defrost start command is generated from a defrost controller according to information from a defrost condition detector 11 at the time of heating operation, a switching valve 7 is first opened, part of high temperature and high pressure gas refrigerant from a compressor 1 is introduced into an outdoor side heat exchanger 5 via a bypass circuit 6, and frost adhered to the exchanger 5 is melted. Thereafter, when frost melting is proceeded and a detected temperature of the detector 11 exceeds a predetermined threshold value, a four-way valve 4 is switched to switch it to a reverse cycle. The valve 7 is closed after a predetermined time is elapsed, all high temperature and high pressure gas refrigerant is introduced into the exchanger 5, and front adhered to the exchanger 5 is melted by the heat of the refrigerant. |
