• Evaporating temperature -30~-60℃, especially for high quality low temperature cold room such as tuna room and blast freezing. • 2-stage screw in parallel with intermediate economizer to provide high liquid subcooling. COP is 30% higher than 1-stage screw rack. • Individual compressor offers capacity unloading plus compressors on-off control, provide sufficient capacity regulating stages to save energy under partial load condtion. • Touch view screen + PLC controller, controlled program dedicatedly developed for 2-stage screw rack, provide stable and reliable control. Support remote access through internet. • Low discharge temperature and vibration, high reliability • Compact design, small space, convenient installation.