Tyler Refrigeration Corporation

American Standard Inc.

Kwok K Fung

Fayez F Ibrahim

A compressor control system for a commercial refrigeration system includes a variable speed compressor and multiple fixed speed compressors. The control system calculates a variable which fluctuates according to the desired capacity of the system and is calculated as a function of the difference between a variable indicative of the refrigeration load on the system, such as compressor suction pressure, and a target value. A 'PID' proportional-integral-differential (PID) controller is used in which terms have been added which fluctuate as a function of the square of the difference between the sensed variable and the target value and as a function of the second derivative of the control variable with respect to time. Fixed speed compressors are turned on or off and the speed of the variable speed compressor is adjusted to bring the actual refrigeration capacity of the system in line with the system refrigeration requirements.

Control for commercial refrigeration system

In an island type refrigeration display cabinet, a top aperture containing two oppositely disposed louvers for discharging oppositely directed coplanar air curtain sections, to form a single air curtain of multiple section in the top aperture of the display cabinet. Preferably, the cabinet also includes means for withdrawing air from the interior display space of the cabinet and forcing the air through a bifurcated conduit. Each bifurcation of the conduit is flowably connected to one of the respective louvers in the top opening of the display cabinet. Each bifurcation of the conduit also includes means for refrigerating the air flowing through the conduit to the louvers.

Island type refrigeration display cabinet

A refrigeration system for a display case including electronic means for controlling an expansion valve and a refrigerant compressor used in the system. The expansion valve is cycled between open and close positions to modulate refrigerant flow into an evaporator coil. A microprocessor controls the operation of the expansion valve in response to: (a) the relationship of the temperature of air that has passed over the evaporator coil to multiple upper and lower limits (b) time integrated temperature deviations beyond preselected limits (c) upward or downward trend of the differential in temperature in the refrigerant during its flow through the evaporator coil, and (d) extreme deviation of the temperature of air that has passed over the evaporator coil. Compressor cut-in and cut-out pressures are also adjusted by the control in response to these air and refrigerant temperatures. In addition, the various limits may be adjusted according to a night setback schedule, and an alarm is provided to warn of relatively long-term deviation of the controlled temperature.

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Niles, MI, United States of America

Kwok K Fung