Refrigeration monitoring system and method

1. A system comprising:

a refrigeration circuit including a condenser and a compressor having a motor;

a first sensor producing a signal indicative of a detected condenser temperature of said condenser;

a second sensor producing a signal indicative of one of current and power drawn by said motor; and

processing circuitry in communication with said first sensor and said second sensor and operable to determine a derived, non-measured condenser temperature by referencing said current or power signal on a map of current or power versus condenser temperature, said processing circuitry operable to compare said derived condenser temperature to said detected condenser temperature to determine a charge level of said refrigeration circuit.

2. The system of claim 1 , wherein said processing circuitry determines an overcharge condition or an undercharge condition if said derived condenser temperature varies from said detected condenser temperature by a predetermined amount and determines an adequate-charge condition if said derived condenser temperature varies from said detected condenser temperature less than said predetermined amount.

3. The system of claim 2 , wherein said processing circuitry controls said refrigeration circuit based on said detected condenser temperature when said normal-charge condition is determined and controls said refrigeration circuit based on said derived condenser temperature when said overcharge condition or said undercharge condition is determined.

4. The system of claim 1 , wherein said first sensor is positioned at one of an outlet and a mid-point of said condenser.

5. The system of claim 1 , wherein said processing circuitry determines an adequate-charge condition when said detected condenser temperature is representative of a saturated condensing temperature.

6. The system of claim 1 , wherein said processing circuitry determines one of an overcharge condition and an undercharge condition when said detected condenser temperature is not representative of a saturated condensing temperature.

7. The system of claim 1 , further comprising a second third sensor producing a signal indicative of a liquid-line temperature.

8. The system of claim 7 , wherein said processing circuitry determines a subcooling based on said liquid-line temperature.

9. The system of claim 1 , wherein said processing circuitry determines said derived condenser temperature independent from information received from said first sensor.

10. A method comprising:

detecting by a first sensor a temperature of a condenser;

communicating said detected condenser temperature to processing circuitry;

deriving by said processing circuitry a non-measured temperature of said condenser by referencing one of current and power drawn by a compressor on a map of current or power versus condenser temperature;

comparing by said processing circuitry said derived condenser temperature with said detected condenser temperature; and

determining one of an overcharge condition, an undercharge condition, and an adequate-charge condition based on said comparing.

11. The method of claim 10 , wherein one of said overcharge condition and said undercharge condition is determined when said derived condenser temperature deviates from said detected condenser temperature by more than a predetermined amount.

12. The method of claim 11 , wherein said adequate-charge condition is determined when said derived condenser temperature deviates from said detected condenser temperature by a value that is less than or equal to said predetermined amount.

13. The method of claim 10 , wherein said adequate-charge condition is determined when said derived condenser temperature deviates from said detected condenser temperature by a value that is less than or equal to said predetermined amount.

14. The method of claim 10 , further comprising controlling by said processing circuitry at least one of a refrigeration circuit and a compressor based on said detected condenser temperature when said adequate-charge condition is determined and controlling by said processing circuitry at least one of said refrigeration circuit and said compressor based on said derived condenser temperature when one of said overcharge condition or said undercharge condition is determined.

15. The method of claim 10 , further comprising determining said adequate-charge condition when said detected condenser temperature is representative of a saturated condensing temperature.

16. The method of claim 10 , further comprising determining one of said overcharge condition and said undercharge condition when said detected condenser temperature is not representative of said saturated condensing temperature.

17. The method of claim 10 , further comprising detecting by a second sensor a signal indicative of a liquid-line temperature.

18. The method of claim 17 , further comprising determining by said processing circuitry a subcooling based on said liquid-line temperature.

19. The method of claim 10 , wherein said deriving said condenser temperature includes deriving said condenser temperature based on information independent from information received from said first sensor.