Patent ID: 8881541

Claim:
A cooling system, comprising: a cabinet having an air inlet and an air outlet; an air moving unit disposed in the cabinet; a tandem compressor, a condenser, an electronic expansion valve and an evaporator arranged in a direct expansion cooling circuit; the tandem compressor including a variable capacity digital scroll compressor and a fixed capacity scroll compressor; a controller coupled to the electronic expansion valve that controls the electronic expansion valve, the controller selecting which of a plurality of superheat control modes to use in operating the electronic expansion valve based on control parameters and a current operating status of each of the variable capacity digital scroll compressor and fixed capacity scroll compressor of the tandem compressor; wherein the plurality of superheat control modes include a gated mode, a system mapping mode and a constant mode, wherein: in the gated mode, each time the variable capacity digital scroll compressor unloads, the controller drives the electronic expansion valve from its current position down to a minimum open position until the variable capacity digital compressor stops unloading and once the variable capacity digital scroll compressor stops unloading, the controller adjusts the position of the electronic expansion valve to achieve a desired superheat; in the system mapping mode, each time the variable capacity digital scroll compressor unloads, the controller retaining the electronic expansion valve in its current position until the variable capacity digital scroll compressor stops unloading and once the variable capacity digital compressor stops unloading, the controller adjusts the position of the electronic expansion valve to achieve a desired superheat; and in the constant mode, the controller adjusts the position of the electronic expansion valve to achieve a desired superheat regardless of whether the variable capacity digital scroll compressor is unloading or loading.