| 摘要 |
PURPOSE:To make it possible to defrost on outdoor heat exchanger during heating operation in continuous mode by changing over the flowing direction of refrigerant to the opposite direction, retaining the flow direction of refrigerant to each indoor unit, and maintaining simultaneously the pressure of the refrigerant which flows into an indoor heat exchanger at a specified value. CONSTITUTION:When heating operation mode is set with indoor units C1 and C2, and cooling operation mode is set with an indoor unit C3, solenoid on/off valves 9, 25, 35, and 46 are opened while solenoid on/off valves 26, 36, and 45 are closed. Furthermore, refrigerant flow rate control valves 2 and 6 are closed. The temperature of an outdoor heat exchanger 3 is detected with a heat exchanger temperature sensor 11. When the detected temperature drops below zero deg.C, the refrigerant flow rate control valves are opened while the solenoid on/off valve 9 is closed, there by defrosting with the heat of refrigerant. During this defrosting operation, a refrigerant pressure sensor 13 detects the pressure of refrigerant which flows into the indoor units C1 and C2 on the heating side and controls the opening of refrigerant flow rate control valves 21 and 31 so that the detected pressure may be constant with the specified values. |
