Method of determining refrigerant charge level in a space temperature conditioning system

In a space temperature conditioning system having a condenser, an evaporator and a compressor for circulating a vapor compression refrigerant between the evaporator and the condenser, a method of determining refrigerant charge level, comprising the steps of:

• establishing a relationship between refrigerant charge level and a plurality of system operating parameters for a plurality of known refrigerant charge levels, independent of ambient temperature conditions;
• operating the system;
• measuring said plurality of system operating parameters while the system is in operation;
• determining the refrigerant charge level based on said relationship in response to said measuring.

In a space temperature conditioning system having a condenser, and an evaporator and a compressor for circulating a vapor compression refrigerant between the evaporator and the condenser, a method of determining refrigerant charge level, comprising the steps of:

• establishing a relationship between refrigerant charge level and at least first, second and third system operating parameters for a plurality of known refrigerant charge levels, independent of ambient temperature conditions, said first system operating parameter corresponding to refrigerant subcooling, said second system operating parameter corresponding to refrigerant pressure at a selected location on a discharge side of the condenser, said third system operating parameter corresponding to refrigerant pressure at a selected location on a suction side of the compressor;
• operating the system to cool air passing through the evaporator;
• measuring said first, second and third system operating parameters while the system is in operation;
• and
• determining refrigerant charge level based on said relationship in response to said measuring.