Air conditioner with refrigerant quantity judging mode

An air conditioner comprising:

• a refrigerant circuit including
• a heat source unit including a compressor having a variable operation capacity and a heat source heat exchanger,
• a utilization unit including a utilization expansion mechanism and a utilization heat exchanger, and
• refrigerant communication pipes connecting the compressor, the heat source heat exchanger, the utilization expansion mechanism and the utilization heat exchanger;
• a heat source controller controlling the compressor and the heat source heat exchanger;
• a utilization controller controlling the utilization expansion mechanism and the utilization heat exchanger;
• and
• an accumulator connected to an intake side of the compressor and configured to accumulate excess refrigerant generated in the refrigerant circuit depending on an operation load of the utilization unit,
• the heat source controller and the utilization controller controlling the compressor, the heat source heat exchanger, the utilization expansion mechanism and the utilization heat exchanger such that the refrigerant circuit performs at least a cooling operation that causes the heat source heat exchanger to operate as a condenser of refrigerant compressed in the compressor and causes the utilization heat exchanger to operate as an evaporator of the refrigerant condensed in the heat source heat exchanger,
• the heat source controller and the utilization controller further controlling the compressor, the heat source heat exchanger, the utilization expansion mechanism and the utilization heat exchanger such that the air conditioner switches between and operates in a normal operation mode and a refrigerant quantity judging operation mode, with
• the heat source unit and the utilization unit being controlled depending on the operation load of the utilization unit in the normal operation mode,
• the utilization heat exchanger operating as an evaporator in the refrigerant quantity judging operation mode,
• the utilization expansion mechanism being controlled such that a degree of superheating of the refrigerant in an outlet of the utilization heat exchanger becomes a positive value in the refrigerant quantity judging operation mode, and
• the variable operation capacity of the compressor being variably controlled such that evaporation pressure of the refrigerant in the utilization heat exchanger becomes constant in the refrigerant quantity judging operation mode, and
• the heat source controller and the utilization controller judging whether or not the refrigerant circuit is filled with an appropriate quantity of refrigerant in the refrigerant quantity judging operation mode based on
• a degree of subcooling of the refrigerant occurring between within the heat source heat exchanger and an outlet of the heat source heat exchanger, or
• an operation state quantity that varies depending on variations in the degree of subcooling.