Refrigerating system employing a compressor for single or multi-stage operation with capacity control

Claim 1

A refrigeration system having a closed circuit serially including a multi-stage compressor, a condenser, an economizer, an expansion device and an evaporator, a branch line connected to said closed circuit intermediate said condenser and said economizer and having a flow path including a first valve, an expansion device, and said economizer and connected to said compressor at an interstage location, said system including a microprocessor for controlling said system responsive to zone and system inputs, said compressor comprising: a first stage including at least two banks; a second stage; said banks of said first stage have discharge chambers and said second stage has a suction chamber; said second stage has a discharge chamber and said discharge chambers of said first stage and said suction chamber of said second stage are fluidly connected via a flow path which extends through said discharge chamber of said second stage; means for unloading one of said banks of said first stage; means for unloading one of said first and second stages; said microprocessor controlling said first valve, said means for unloading one of said banks and said means for unloading one of said first and second stages whereby said system can be operated single stage, two stage with or without economized flow and with or without unloading of said one of said banks of said first stage.