AIR CONDITIONER

PURPOSE:To stably perform a proper operation even when the operating conditions are changed, by a method wherein the opening degree of a pressure reducing device is controlled during cooling operation so that the difference between temperatures detected by temperature detectors reaches a set value, and the combustion rate of a refrigerant heater is controlled only when the temperature difference exceeds the first set value during heating operation so that the temperature difference reaches a second set value higher than a first set value. CONSTITUTION:In cooling operation, the temperature of an indoor heat exchanger 6 is detected by a first temperature sensor 16, the outlet temperature of the indoor heat exchanger 6 by a second temperature sensor 17, and the opening degree of an expansion valve 5 is controlled so that difference between the detected temperatures reaches a set value. In cooling operation, the temperature difference represents super-heating state of the refrigerant at the outlet of the indoor heat exchanger 6, and when the temperature difference is within a specified proper range, a compressor 1 can be stably operated regardless of changes in the refrigerant conditions without over-heating of the compressor 1 and deterioration in the durability caused by liquid pack. In heating operation, the combustion rate of a refrigerant heater 9 is controlled only when the difference between the temperatures detected by the temperature sensors 16 and 17 exceeds the first set value so that the temperature difference reaches a second set value being higher than the first one.