An air-conditioning apparatus, including a compressor, a refrigerant flow switching device, a heat source side heat exchanger, a first expansion device, and an intermediate heat exchanger connected via refrigerant pipes, that constitutes a refrigerant circuit circulating a refrigerant, a pump, the intermediate heat exchanger, and a use side heat exchanger connected via heat medium pipes, that constitutes a heat medium circuit, the air-conditioning apparatus comprising:
- a second expansion device provided on an upstream side of the heat source side heat exchanger with respect to flow of the refrigerant during a heating operation, the second expansion device is disposed between the heat source side heat exchanger and the intermediate heat exchanger;
- an accumulator configured to accumulate excess refrigerant provided on an upstream side of the compressor with respect to the flow of the refrigerant, the accumulator is disposed between the compressor and the heat source side heat exchanger;
- a suction injection pipe, having one end connected on an upstream side of the second expansion device with respect to the flow of the refrigerant during the heating operation, and another end connected to a flow channel between a suction side of the compressor and the accumulator;
- a third expansion device provided on the suction injection pipe;
- a medium pressure detector configured to detect one of a refrigerant pressure and a refrigerant saturation temperature on an upstream side of the second expansion device with respect to the flow of the refrigerant during the heating operation, to detect pressure of the refrigerant that was depressurized by the first expansion device as medium pressure refrigerant which has a medium pressure, the medium pressure being lower than a pressure of the refrigerant supplied to the intermediate heat exchanger serving as a condenser, and being higher than a pressure of the refrigerant flowing out from the heat source side heat exchanger serving as an evaporator;
- a discharge refrigerant temperature detector configured to detect a discharge refrigerant temperature of the refrigerant which is discharged from the compressor;
- and a controller configured to control an opening degree of the second expansion device and the third expansion device based on a detection result from the medium pressure detector and the discharge refrigerant temperature detector;
- wherein, inside the refrigerant pipes, the refrigerant has a higher discharge refrigerant temperature than R410A, and the controller performs medium pressure control that controls the opening degree of the second expansion device based on a deviation between a target value of medium pressure and one of a detection result of the medium pressure detector and a predicted value, determines whether the discharge refrigerant temperature transiently rises and determines whether the discharge refrigerant temperature is in a steady state, responsive to the discharge refrigerant temperature of the compressor being determined to transiently rise and after starting the medium pressure control, performs activation control, and responsive to the discharge refrigerant temperature of the compressor being determined to be in the steady state and after starting the medium pressure control, performs steady-state control, regulates a flow rate of the refrigerant to supply to the suction side of the compressor via the suction injection pipe, closes the third expansion device until one of the activation control and the steady-state control is started, in the activation control, controls the opening degree of the third expansion device based on a detection result of the discharge refrigerant temperature detector and a first discharge refrigerant temperature target value, and, in the steady-state control, controls the opening degree of the third expansion device based on the detection result of the discharge refrigerant temperature detector and a second discharge refrigerant temperature target value that differs from the first discharge refrigerant temperature target value.