Patent ID: 8290722

Claim:
A method for indicating the level of refrigerant charge in a refrigerant vapor compression system having a compressor, a condenser coil, an expansion device and an evaporator coil connected in serial relationship in refrigerant flow circuit, comprising the steps of sensing the pressure of the refrigerant at a location in the refrigerant flow circuit whereat the refrigerant is near or above normally full charge in a liquid state only and generating a first signal indicative of the sensed refrigerant pressure; sensing the temperature of the refrigerant at the same location in the refrigerant flow circuit and generating a second signal indicative of the sensed refrigerant temperature; calculating in real-time an instantaneous value for the degrees of subcooling present based upon the sensed refrigerant pressure and the sensed refrigerant temperature; storing the calculated instantaneous value for the degrees of subcooling in a dedicated data location associated with the sensed refrigerant temperature; accumulating the calculated instantaneous value for the degrees of subcooling associated with each respective sensed refrigerant temperature within the respective data location associated with the respective sensed refrigerant temperature; calculating an average value for the degrees of subcooling present based upon the accumulated instantaneous values for the degrees of subcooling; determining a system refrigerant charge status based upon a consideration of both the instantaneous value for the degree of subcooling and the average value for the degree of subcooling; outputting an indication of the system refrigerant charge status.