Heat pump system with multi-stage centrifugal compressors

摘要

The heat pump system includes a first and a second centrifugal compressor arranged in series relation in a system including interstage expansion of the refrigerant. A pair of parallel circuits is provided for controlling the energization of the compressors in a sequence in which the first to start compressor must be energized to obtain completion of the second parallel circuit required for energization of the second to start compressor. The start of the second compressor is delayed for a period permitting the first compressor to come up to speed and the first circuit controlling the energization of the first compressor will be interrupted unless the second compressor has started within a short period of time after the time delay in starting the second compressor.