Protection methods and systems for refrigeration systems suitable for a

Abstract

Calibrated methods and systems for protecting refrigerant motor/compressors against overload and loss of refrigerant conditions, independent of compressor and system size, while avoiding the need for a plurality of sensors. The disclosed methods and systems are generic in the sense that they may be employed in a variety of different air conditioner or heat pump models of different sizes and capacities, without being specifically tailored for a particular model, although a factory calibration adjustment is required. The disclosed methods and systems sense loading on the compressor motor, and make control decisions based thereon. A permanent compressor motor reference loading is established when the refrigeration system has a known correct refrigerant charge and the motor/compressor has a known load. This is typically accomplished in the factory after a predetermined stabilization interval has elapsed following initial start up of the motor/compressor. During operation thereafter, at least a representation of prevailing compressor motor loading is at least periodically sensed. A low-load condition indicative of a loss of refrigerant or of insufficient evaporator airflow is recognized if the prevailing loading is less than a low load threshold loading established as a first predetermined function of the permanent reference loading. A high load condition indicative of an excessive load on the motor/compressor is recognized if the prevailing loading exceeds a high load threshold loading established as a second predetermined function of the permanent reference loading. In either case, the motor/compressor is deenergized.