MULTI-UNIT AIR CONDITIONER, OUTDOOR UNIT THEREOF, AND METHOD OF CONTROLLING THE MULTI-UNIT AIR CONDITIONER

摘要

PPROBLEM TO BE SOLVED: To install an outdoor unit and an indoor unit with difference in height more than that in a conventional one while easily installing them and preventing refrigerant pressure in a refrigerant circuit from being excessive without performing complicated control, even when the difference in height in installing the outdoor unit and the indoor unit is large. PSOLUTION: The opening control of a pressure reducing expansion valve 40 is performed only when the refrigerant pressure on a high-pressure side in the outdoor unit 10 is high during a cooling operation. In the opening control of the pressure reducing expansion value 40, the opening of the pressure reducing expansion valve 40 is determined on the basis of a driving frequency of a compressor 16 at that point in time, i.e., a volumetric flow volume of a refrigerant, a pressure reduction in the pressure reducing expansion valve 40 is suppressed when the volumetric flow volume of the refrigerant is large and a pressure loss in a communication pipe 30 is large, and the pressure reduction in the pressure reducing expansion valve 40 is increased when the volumetric flow volume of the refrigerant is small and the pressure loss in the communication pipe 30 is small, whereby the amount of pressure reduction of the refrigerant is adjusted in the total refrigerant circuit from the compressor 16 to an indoor expansion valve 22. Thus the refrigerant pressure is properly reduced and suppressed constantly regardless of operating conditions so as to prevent the excess refrigerant pressure from being applied to the indoor expansion valve. PCOPYRIGHT: (C)2010,JPO&INPIT