Refrigerant charge level detection

1. 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.

2. The system of claim 1 , wherein the controller is configured to determine at least one target pressure value by converting at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant.

3. The system of claim 1 , wherein the controller is configured to compare the output indicative of sensed pressure to at least one target pressure value to determine if the sensed pressure is below a minimum threshold indicative of a low refrigerant charge level, and to display on the display device an indication of a low refrigerant charge level.

4. The system of claim 1 , wherein the controller is configured to compare the output indicative of sensed pressure to at least one target pressure value to determine if the sensed pressure exceeds a threshold indicative of a high refrigerant charge level, and to display on the display device an indication of a high refrigerant charge level.

5. The system of claim 1 , wherein the controller is configured to determine a difference between the output indicative of sensed pressure and at least one target pressure value, and to display on the display device an indication of a low refrigerant charge level where the difference exceeds a threshold indicative of a low refrigerant charge level.

6. The system of claim 1 , wherein the controller is a processor of a control for activating at least a compressor of an air conditioner or heat pump.

7. 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 configured to determine at least one target pressure value by converting a sum of the sensed temperature of the liquid refrigerant line and a sub-cool temperature value into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant.

8. 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 configured to determine at least one target pressure value by converting at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant; and

wherein the controller is configured to determine at least two target pressure values from the sum of the corresponding pressure value and at least one pressure offset value.

9. 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 configured to determine a plurality of target pressure values, based on a temperature-pressure conversion of at least the sensed temperature of the liquid refrigerant line, to determine if the sensed pressure is within a range defined by at least two target pressure values representative of a sensed refrigerant level that is above, below or within an acceptable range, and the display is configured to display at least one of one or more indicators for indicating that the sensed refrigerant level is above, below or within the acceptable range.

10. The system of claim 9 , wherein the display displays one or more indicators representing a relative scale for indicating whether the sensed refrigeration level is above, below or within the acceptable range.

11. 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 configured to determine at least two target pressure values from a conversion of at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a refrigerant temperature-pressure relationship, and the display is configured to display an indication of whether the refrigerant charge is within or outside of an acceptable range where the output indicative of sensed pressure is respectively within or outside of an acceptable range defined by the at least two target pressure values.

12. 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 configured to determine a plurality of target pressure values, and to compare the output indicative of sensed pressure to the plurality of target pressure values to determine if the sensed pressure is between at least two target pressure values that are indicative of an acceptable range for a sensed refrigerant charge level.

13. The system of claim 12 , 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.

14. 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 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, and 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 at least one target pressure value determined from the sensed temperature of the liquid refrigerant line, 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.

15. A method for monitoring refrigerant charge, the method comprising:

sensing and providing a first 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;

sensing and providing a second output indicative of a sensed pressure in the liquid refrigerant line;

determining at least one target pressure value from the output indicative of the sensed temperature of the liquid refrigerant line;

determining 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

displaying an indication of whether the level of refrigerant charge is at, above or below an acceptable level;

wherein determining at least one target pressure value comprises determining at least two target pressure values from a conversion of at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a refrigerant temperature-pressure relationship, and displaying an indication comprises displaying an indication of whether the refrigerant charge is within or outside of an acceptable range where the output indicative of sensed pressure is respectively within or outside of an acceptable range defined by the at least two target pressure values.

16. The method of claim 15 , wherein determining at least one target pressure value comprises converting at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant.

17. The method of claim 15 , wherein determining if the level of refrigerant charge is at, above or below an acceptable level comprises comparing the output indicative of sensed pressure to at least one target pressure value to determine if the sensed pressure is below a minimum threshold indicative of a low refrigerant charge level, and displaying an indication comprises displaying an indication of a low refrigerant charge level.

18. The method of claim 15 , wherein determining if the level of refrigerant charge is at, above or below an acceptable level comprises comparing the output indicative of sensed pressure to at least one target pressure value to determine if the sensed pressure exceeds a threshold indicative of a high refrigerant charge level, and displaying an indication comprises displaying an indication of a high refrigerant charge level.

19. A method for monitoring refrigerant charge, the method comprising:

sensing and providing a first 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;

sensing and providing a second output indicative of a sensed pressure in the liquid refrigerant line;

determining at least one target pressure value from the output indicative of the sensed temperature of the liquid refrigerant line;

determining 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

displaying an indication of whether the level of refrigerant charge is at, above or below an acceptable level;

wherein determining at least one target pressure value comprises converting a sum of the sensed temperature of the liquid refrigerant line and a sub-cool temperature value into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant.

20. The method of claim 19 , wherein determining at least one target pressure value comprises determining at least two target pressure values from a conversion of at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a refrigerant temperature-pressure relationship, and displaying an indication comprises displaying an indication of whether the refrigerant charge is within or outside of an acceptable range where the output indicative of sensed pressure is respectively within or outside of an acceptable range defined by the at least two target pressure values.

21. A method for monitoring refrigerant charge, the method comprising:

sensing and providing a first 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;

sensing and providing a second output indicative of a sensed pressure in the liquid refrigerant line;

determining at least one target pressure value from the output indicative of the sensed temperature of the liquid refrigerant line;

determining 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

displaying an indication of whether the level of refrigerant charge is at, above or below an acceptable level;

wherein determining at least one target pressure value comprises converting at least the sensed temperature of the liquid refrigerant line into a corresponding pressure value based on a temperature-pressure relationship for the refrigerant; and

wherein determining at least one target pressure value comprises determining at least two target pressure values from the sum of the corresponding pressure value and at least one pressure offset value.

22. A method for monitoring refrigerant charge, the method comprising:

sensing and providing a first 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;

sensing and providing a second output indicative of a sensed pressure in the liquid refrigerant line;

determining at least one target pressure value from the output indicative of the sensed temperature of the liquid refrigerant line;

determining 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

displaying an indication of whether the level of refrigerant charge is at, above or below an acceptable level;

wherein determining at least one target pressure value comprises determining a plurality of target pressure values based on a temperature-pressure conversion of at least the sensed temperature of the liquid refrigerant line, and determining if the level of refrigerant charge is at, above or below an acceptable level comprises determining if the sensed pressure is within a range defined by at least two target pressure values representative of a sensed refrigerant level that is above, below or within an acceptable range, and displaying an indication comprises displaying at least one of one or more indicators for indicating that the sensed refrigerant level is above, below or within the acceptable range.

23. The method of claim 22 , wherein displaying comprises displaying one or more indicators representing a relative scale for indicating whether the sensed refrigeration level is above, below or within the acceptable range.