PURPOSE: To assure a heating capability of an indoor unit being operated without having any relation with a length of a connecting pipe and temperature of surrounding air by a method wherein a degree of opening or closing of an electrical expansion valve corresponding to a stopped indoor unit is adjusted in response to a detected temperature of a saturation temperature sensor when a few number of heating devices are operated.

CONSTITUTION: In the case that the surrounding air temperature is high, only an indoor unit 109 is operated to heat and a low pressure of a compressor 103 shows a high temperature, so that the detected temperature of a saturation temperature sensor 118 is also increased, a degree of opening of instruction for each of the electrical expansion valves 106 and 107 is made lower than that of a low pressure adjusting device 1 through an electrical expansion valve control device 113, a flow rate of refrigerant flowing in the indoor units 110 and 111 is reduced and then the heating capability of the indoor unit 109 is assured. As the low pressure is increased, the detected temperature of the saturation temperature sensor 118 is also increased, resulting in that when it reaches a value more than a specified value, the degree of opening of each of the electrical expansion valves 106 and 107 is reduced by the low pressure adjusting device 1, a flow rate of the refrigerant flowing in each of the indoor units 110 and 111 not being operated can be reduced and a heating capability of the indoor unit 109 can be increased.