Abstract: Method for controlling a multi-type air conditioner having a plurality of indoor units each with an expansion valve, an indoor heat exchanger, and an indoor fan, some of which heat rooms, and rest of which are turned off, including the steps of (S11) defining a saturation temperature of refrigerant by using a heating cycle of the refrigerant, and Mollier chart, (S12) measuring a temperature of the refrigerant stagnant at the turned off indoor units, (S13) determining if a temperature difference of the refrigerant temperature and the saturation temperature is within a temperature range preset at a control part, (S14) opening the expansion valves of the turned off indoor units, if the temperature difference is within the temperature range preset at the control part, and (S15) closing the expansion valve of the turned off indoor units, if the temperature difference is not within the temperature range preset at the control part, whereby minimizing stagnation of refrigerant at turned off indoor units during some o

Abstract: There is provided a system and method for controlling a temperature of a refrigerant in an air conditioner, in which a supercooling degree and/or a superheating degree can be secured by controlling a difference in refrigerant temperatures of a pipe connecting one or more indoor units to one or more outdoor units, and a flow of a specific refrigerant. The system includes: one or more indoor units; one or more outdoor units; a high-pressure pipe and a low-pressure pipe for connecting the indoor units and the outdoor units; and a refrigerant temperature control unit coupled to the high-pressure pipe and the low-pressure pipe, for performing a heat exchange with respect to flowing refrigerants by coupling an inner pipe to an outer pipe, the inner pipe passing through the another pipe.