Patent ID: 8648729

Claim:
A refrigerant charge monitoring system comprising: a first sensor operable to provide an output indicative of a sensed refrigerant liquid temperature of a liquid refrigerant line that is within or extending from an outlet of a condenser coil of an air conditioner or heat pump unit; a second sensor operable to provide an output indicative of a sensed refrigerant liquid pressure of the liquid refrigerant line; and a controller configured to determine at least one target pressure value from the output indicative of the sensed refrigerant liquid temperature, the controller being configured to determine if the level of refrigerant charge is at, above, or below an acceptable level based on a comparison of the output indicative of sensed refrigerant liquid pressure to the at least one target pressure value; wherein the controller is a processor of a thermostat that is configured to wirelessly receive the output indicative of sensed pressure and the output indicative of a sensed temperature of a liquid refrigerant line.