Method for detection of loss of refrigerant

A method for detecting in real-time a refrigerant charge loss in a refrigerant vapor compression system having a refrigerant circuit including a refrigerant compression device, a refrigerant heat rejection heat exchanger, an evaporator and an electronic expansion valve operatively associated with the evaporator, the method comprising:

• determining at a controller whether 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 the electronic expansion valve exceeds a preset degree of openness for a preset time of period;
• in response to both the sensed evaporator outlet superheat exceeding the target evaporator outlet superheat by at least the preset amount of superheat and the sensed degree of openness of the electronic expansion valve exceeding the preset degree of openness for the preset time of period, determining at the controller whether at least one air temperature of a sensed supply air temperature of a flow of air having traversed the evaporator or a sensed return air temperature of a flow of air returning to the evaporator is changing at a rate less than a preset air temperature rate of change;
• and
• in response to the at least one air temperature of the sensed supply air temperature of a flow of air having traversed the evaporator or the sensed return air temperature of a flow of air returning to the evaporator changing at a rate less than the preset air temperature rate of change, the controller generating a service alarm indicating a loss of charge warning.