Abstract: An air conditioning apparatus includes a refrigerant circuit performing an air-warming operation by circulating refrigerant through the compressor, indoor heat exchanger, expansion valve, and outdoor heat exchanger in order. The outdoor heat exchanger has flat perforated tubes arrayed vertically in multiple levels. The heat transfer tubes are sectioned into main and subordinate heat exchange parts. Upper and lower exit-entry spaces are formed in the outdoor heat exchanger. When an oil-accumulation-resolving criterion is met during the air-warming operation, low-refrigerant-circulation control, in which the refrigerant is circulated through the compressor, indoor heat exchanger, expansion valve, and outdoor heat exchanger in order, is performed for a predetermined time with an operating capacity of the compressor having been lowered to a predetermined capacity.

Abstract: An air-conditioning apparatus includes an outdoor unit, an indoor unit having an indoor heat exchanger, and a controller for executing a pump down operation. The outdoor unit has an accumulator of a capacity (Va), a compressor, an outdoor heat exchanger, an expansion valve, a large-diameter tube, which are joined by refrigerant pipes. The capacity (Vhi) of the indoor heat exchanger is greater than the capacity (Vho) of the outdoor heat exchanger. The large-diameter tube, which is larger in diameter than the refrigerant pipes, is provided so that the capacity (Vt) of the large-diameter tube satisfies the formula: capacity (Vt)>capacity (Vhi)?capacity (Vho)?capacity (Va).

Abstract: An air conditioning apparatus includes a refrigerant circuit performing an air-warming operation by circulating refrigerant through the compressor, indoor heat exchanger, expansion valve, and outdoor heat exchanger in order. The outdoor heat exchanger has flat perforated tubes arrayed vertically in multiple levels. The heat transfer tubes are sectioned into main and subordinate heat exchange parts. Upper and lower exit-entry spaces are formed in the outdoor heat exchanger. When an oil-accumulation-resolving criterion is met during the air-warming operation, low-refrigerant-circulation control, in which the refrigerant is circulated through the compressor, indoor heat exchanger, expansion valve, and outdoor heat exchanger in order, is performed for a predetermined time with an operating capacity of the compressor having been lowered to a predetermined capacity.

Abstract: An air-conditioning apparatus includes an outdoor unit, an indoor unit having an indoor heat exchanger, and a controller for executing a pump down operation. The outdoor unit has an accumulator of a capacity (Va), a compressor, an outdoor heat exchanger, an expansion valve, a large-diameter tube, which are joined by refrigerant pipes. The capacity (Vhi) of the indoor heat exchanger is greater than the capacity (Vho) of the outdoor heat exchanger. The large-diameter tube, which is larger in diameter than the refrigerant pipes, is provided so that the capacity (Vt) of the large-diameter tube satisfies the formula: capacity (Vt)>capacity (Vhi)?capacity (Vho)?capacity (Va).