One of the main advantages of parallel compressor systems is their ability to closely match the refrigeration load. Parallel systems apply two or more compressors to a common suction header and a common discharge header. (See Figure 1.)
Under high evaporator heat loading, all compressors may be operating. As the evaporator's heat load decreases, compressors will start to cycle off. A pressure transducer connected to the common suction header and hardwired to a microprocessor senses the ever-changing refrigeration load.