Method and apparatus for monitoring a refrigeration-cycle system

1. A method for monitoring operation of a refrigerant-cycle system, comprising:

measuring a first pressure of refrigerant input to a compressor of the refrigerant-cycle system using a first pressure sensor;

measuring a first temperature of the refrigerant input to the compressor using a first temperature sensor;

measuring a second pressure of refrigerant output by the compressor and input to a condenser of the refrigerant-cycle system using a second pressure sensor;

measuring a second temperature of refrigerant output by the condenser using a second temperature sensor;

measuring a third pressure of refrigerant output by the condenser using a third pressure sensor;

measuring current to the compressor using an electrical sensor; and

using a processing system, determining whether the refrigerant-cycle system is at least one of undercharged or overcharged with refrigerant based on the first temperature, the first pressure, the second temperature, the second pressure, the third pressure, and the current.

2. The method of claim 1 further comprising:

determining an evaporating temperature based on the first pressure;

determining an evaporator superheat based on a difference between the first temperature and the evaporating temperature;

determining a condensing temperature based on the third pressure;

determining a condenser subcooling based on a difference between the second temperature and the condensing temperature; and

determining whether the refrigerant-cycle system is at least one of undercharged or overcharged with refrigerant based on the first pressure, the evaporator superheat, the second pressure, the condenser subcooling, and the current.

3. The method of claim 2 further comprising determining that the refrigerant-cycle system is at least one of undercharged or overcharged with refrigerant in response to the first pressure being less than a first predetermined value, the evaporator superheat being greater than a second predetermined value, the second pressure being less than a third predetermined value, the condenser subcooling being less than a fourth predetermined value, and the current being less than a fifth predetermined value.

4. A method for monitoring operation of a refrigerant-cycle system, comprising:

measuring a first pressure of refrigerant input to a compressor of the refrigerant-cycle system using a first pressure sensor;

measuring a first temperature of the refrigerant input to the compressor using a first temperature sensor;

measuring a second pressure of refrigerant output by the compressor and input to a condenser of the refrigerant-cycle system using a second pressure sensor;

measuring a second temperature of refrigerant output by the condenser using a second temperature sensor;

measuring a third pressure of refrigerant output by the condenser using a third pressure sensor;

measuring current to the compressor using an electrical sensor; and

using a processing system, determining whether a restriction is present in a refrigerant line of the refrigerant-cycle system based on the first temperature, the first pressure, the second temperature, the second pressure, the third pressure, and the current.

5. The method of claim 4 further comprising:

determining an evaporating temperature based on the first pressure;

determining an evaporator superheat based on a difference between the first temperature and the evaporating temperature;

determining a condensing temperature based on the third pressure;

determining a condenser subcooling based on a difference between the second temperature and the condensing temperature; and

determining whether a restriction is present in the refrigerant line based on the first pressure, the evaporator superheat, the second pressure, the condenser subcooling, and the current.

6. The method of claim 4 , wherein the refrigerant line is connected between an evaporator of the refrigerant-cycle system and the condenser.

7. The method of claim 4 , wherein the refrigerant line is connected between an evaporator of the refrigerant-cycle system and the compressor.

8. The method of claim 4 , wherein the refrigerant line is connected between the compressor and the condenser.

9. The method of claim 5 , wherein the refrigerant line is connected between an evaporator of the refrigerant-cycle system and the condenser.

10. The method of claim 9 further comprising determining that a restriction is present in the refrigerant line in response to the first pressure being less than a first predetermined value, the evaporator superheat being greater than a second predetermined value, the second pressure being less than a third predetermined value, the condenser subcooling being greater than a fourth predetermined value, and the current being less than a fifth predetermined value.

11. The method of claim 5 , wherein the refrigerant line is connected between an evaporator of the refrigerant-cycle system and the compressor.

12. The method of claim 5 , wherein the refrigerant line is connected between the compressor and the condenser.

13. The method of claim 11 further comprising determining that a restriction is present in the refrigerant line in response to the first pressure being less than a first predetermined value, the evaporator superheat being greater than a second predetermined value, the second pressure being less than a third predetermined value, the condenser subcooling being within a predetermined range, and the current being less than a fourth predetermined value.

14. The method of claim 12 further comprising determining that a restriction is present in the refrigerant line in response to the first pressure being greater than a first predetermined value, the evaporator superheat being greater than a second predetermined value, the second pressure being greater than a third predetermined value, the condenser subcooling being within a predetermined range, and the current being greater than a fourth predetermined value.

15. A method for monitoring operation of a refrigerant-cycle system, comprising:

measuring a first pressure of refrigerant input to a compressor of the refrigerant-cycle system using a first pressure sensor;

measuring a first temperature of the refrigerant input to the compressor using a first temperature sensor;

measuring a second pressure of refrigerant output by the compressor and input to a condenser of the refrigerant-cycle system using a second pressure sensor;

measuring a second temperature of refrigerant output by the condenser using a second temperature sensor;

measuring a third pressure of refrigerant output by the condenser using a third pressure sensor;

measuring current to the compressor using an electrical sensor; and

using a processing system, determining whether a metering device connected between the condenser and an evaporator is plugged based on the first temperature, the first pressure, the second temperature, the second pressure, the third pressure, and the current.

16. The method of claim 15 further comprising:

determining an evaporating temperature based on the first pressure;

determining an evaporator superheat based on a difference between the first temperature and the evaporating temperature;

determining a condensing temperature based on the third pressure;

determining a condenser subcooling based on a difference between the second temperature and the condensing temperature; and

determining whether the metering device is plugged based on the first pressure, the evaporator superheat, the second pressure, the condenser subcooling, and the current.

17. The method of claim 16 further comprising determining that the metering device is plugged in response to the first pressure being less than a first predetermined value, the evaporator superheat being greater than a second predetermined value, the second pressure being greater than a third predetermined value, the condenser subcooling being greater than a fourth predetermined value, and the current being less than a fifth predetermined value.