Multi-Air-Conditioner LX for 2004 needs 52% less installation space and has a 24% improved coefficient of performance (COP), as compared with the conventional KX2 series of 20 horsepower class. The compact design and higher COP have been realized by reduction of pressure loss in duct by four-side suction structure of the heat exchanger, optimization of fan and duct, and DC compressor motor, and all models conform to the standard values of the Energy Conservation Law of Japan. The maximum piping length has been extended to 160 meters, the longest in the industry, and by improved collection of running data, installation and maintenance have been made easier.