Capacity control for multi-stage compressors

摘要

In a positive displacement compressor (10) having a plurality of banks (112,114), operation can be multi-staged or single staged. Single stage operation can be of a single bank or plural banks in parallel. Switchover between modes of operation is under the control of a microprocessor (50) responsive to sensed inputs. During pulldown under ambient or condenser entering air temperatures of 100 DEG F, or more, suction modulation is used to limit the suction pressure thereby permitting a switchover to two-stage operation and the use of an economizer (70).