Multi-stage cooling system with tandem compressors and optimized control of sensible cooling and dehumidification

A cooling system, comprising:

• a cabinet having an air inlet and an air outlet;
• an air moving unit disposed in the cabinet;
• a plurality of separate cooling stages including an upstream cooling stage and a downstream cooling stage, the upstream cooling stage having an upstream cooling circuit and the downstream cooling stage having a downstream cooling circuit;
• the upstream and downstream cooling circuits are each a direct expansion refrigeration cooling circuit including an evaporator, a condenser, a tandem compressor and an expansion device, the evaporator having an inlet coupled to an outlet of the expansion device and an outlet coupled to an inlet of the tandem compressor, the tandem compressor having an outlet coupled to an inlet of the condenser and the condenser having an outlet coupled to an inlet of the expansion device;
• each tandem compressor including a fixed capacity compressor and a variable capacity compressor;
• the evaporator of the upstream cooling circuit and the evaporator of the downstream cooling circuit arranged in the cabinet so that air to be cooled passes over them in serial fashion, first over the evaporator of the upstream cooling circuit and then over the evaporator of the downstream cooling circuit;
• and
• a controller coupled to the tandem compressors that in a sensible cooling control controls the fixed capacity compressor and variable capacity compressor of each of the tandem compressors based on a Call for Cooling, also based on which of a plurality of sensible cooling control ranges that the Call for Cooling falls within and also based on whether the Call for Cooling is ramping up or ramping down, wherein when there is an unmet Call for Dehumidification, the controller switching from the sensible cooling control to a dehumidification control and controls the fixed capacity compressor and variable capacity compressor of each of the tandem compressors based on the Call for Dehumidification and also based on which of a plurality of dehumidification control ranges that the Call for Cooling falls within until the Call for Dehumidification has been met and then switching back to the sensible cooling control.