Patent ID: 8466798

Claim:
A refrigerant charge monitoring system, comprising: a first sensor that provides an output indicative of a sensed 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 that provides an output indicative of a sensed pressure in the liquid refrigerant line; a controller configured to determine at least one target pressure value from the output indicative of the sensed temperature of the liquid refrigerant line, 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 pressure to the at least one target pressure value; and a display that displays an indication of whether the level of refrigerant charge is at, above or below an acceptable level; wherein the controller is a communication device for communicating information indicating that the refrigerant charge is at, above or below an acceptable level based on a comparison of the output indicative of sensed pressure to the at least one target pressure value, and the display is a display of a thermostat configured to display an indication of whether the level of refrigerant charge is at, above or below an acceptable level.