US Patent 9869499 Method for detection of loss of refrigerant

A method is provided for detecting in real-time a refrigerant charge loss in a refrigerant vapor compression system. If both a sensed evaporator outlet superheat exceeds a target evaporator outlet superheat by at least a preset amount of superheat and a sensed degree of openness of an electronic expansion valve exceeds a preset degree of openness for a preset time of period, and a sensed air temperature of either a flow of supply air having traversed the evaporator or a flow of return air returning to the evaporator is changing at a rate less than preset air temperature rate of change, a service alarm is generated indicating a loss of charge warning.