CO2 refrigeration system

1. A CO 2 refrigeration system, including: a compressor, a gas cooler, a temperature sensor, and an electronic control system, the electronic control system including a processor device arranged to control operation of the compressor according to input signals received from the temperature sensor, wherein:

(a) the temperature sensor is positioned to read an output temperature of the gas cooler,

(b) the processor device is arranged to compare the measured temperature of the gas cooler output with a lower threshold temperature value, and

(c) in a condition where the processor device determines that the measured temperature is less than or equal to the lower threshold temperature value, the processor device is arranged to initiate an extended rest period for the compressor, and

(d) the processor device is arranged to activate the compressor device when the extended rest period has ended.

2. The refrigeration system according to claim 1 , wherein the temperature sensor is positioned to measure the temperature of the CO 2 refrigerant directly as it exits the gas cooler.

3. The refrigeration system according to claim 1 , wherein the temperature sensor is mounted on at least one of a gas cooler wall and an adjacent conduit.

4. The refrigeration system according to claim 1 , including an upper threshold temperature value stored in memory in the processor device, wherein the processor device is arranged to compare the measured temperature of the gas cooler output with the upper threshold temperature value and wherein in a condition where the processor device determines that the measured temperature is greater than or equal to the upper threshold temperature value, the processor device is arranged to deactivate the compressor.

5. The refrigeration system according to claim 4 , wherein the processor device is arranged to generate a gas cooler alarm signal each time the measured temperature is determined to be greater than or equal to the upper threshold temperature value and wherein the processor device is arranged to shut down the refrigeration system if the number of gas cooler alarms exceeds a predetermined value within a predetermined time period.

6. The refrigeration system according to claim 1 , wherein the extended rest period is a fixed time period.

7. The refrigeration system according to claim 6 , wherein the extended rest period lasts for at least 5 minutes.

8. The refrigeration system according to claim 6 , wherein the extended rest period lasts for at least 8 minutes.

9. The refrigeration system according to claim 6 , wherein the extended rest period lasts for at least 10 minutes.

10. The refrigeration system according to claim 1 , the system further including a clock and the extended rest period is timed by the clock.

11. The refrigeration system according to claim 1 , wherein the lower threshold temperature value is determined by subtracting an offset temperature value from the lower threshold temperature value.

12. The refrigeration system according to claim 11 , wherein the offset temperature value is at least 5° C.

13. The refrigeration system according to claim 11 , wherein the offset temperature value is at least 8° C.

14. The refrigeration system according to claim 11 , wherein the offset temperature value is at least 10° C.

15. The refrigeration system according to claim 11 , wherein the offset temperature value is at least 12° C.

16. The refrigeration system according to claim 1 , wherein the temperature sensor is connected to an auxiliary input of the processor device.

17. The refrigeration system according to claim 1 , the system further including a pressure sensitive device.

18. The refrigeration system according to claim 1 , the system further including a rupturing device that is arranged to rupture when the operating pressure within the refrigeration system reaches a rupture pressure, wherein the processor device is arranged to control operation of the compressor to maintain the refrigeration system operating pressure at a value that is less than the rupture pressure.

19. The refrigeration system according to claim 1 , wherein the processor device includes an interface that is arranged to enable the user to set at least one of the following parameters: the upper threshold temperature value, the lower threshold temperature value, and the length of the extended rest period for the compressor.

20. A method for controlling a compressor in a CO 2 refrigeration system, said CO 2 refrigeration system having a compressor, a gas cooler, a temperature sensor and an electronic control system including a processor device, wherein the method comprises:

(a) measuring CO 2 refrigerant temperature at the output of the gas cooler with the temperature sensor and using the processor device to control operation of the compressor according to input signals received by the processor device from the temperature sensor;

(b) comparing the measured temperature of the gas cooler output with a lower threshold temperature value stored in memory in the processor device;

(c) automatically initiating an extended rest period for the compressor when the processor device determines that the measured temperature is less than or equal to the lower threshold temperature value; and

(d) activating the compressor when the extended rest period has ended.

21. The method according to claim 20 , the method further including comparing the measured temperature of the gas cooler output with an upper threshold temperature value stored in a memory means and automatically deactivating the compressor when the processor device determines that the measured temperature is greater than or equal to the upper threshold temperature value.

22. The method according to claim 21 , the method further including the processor device generating a gas cooler alarm signal each time the measured temperature is determined to be greater than or equal to the upper threshold temperature value.

23. The method according to claim 22 , the method further including the processor device shutting down the refrigeration system if the number of gas cooler alarms exceeds a predetermined value within a predetermined time period.

24. The method according to claim 20 , wherein the extended period is a fixed period of time.

25. The method according to claim 24 , the wherein the extended rest period lasts for at least 3 minutes.

26. The method according to claim 20 , the method further including calculating the lower threshold temperature value by subtracting an offset temperature value from the lower threshold temperature value.

27. The method according to claim 26 , wherein the offset temperature value is at least 8° C.

28. The method according to claim 26 , wherein the offset temperature value is at least 10° C.

29. The method according to claim 26 , wherein the offset temperature value is at least 12° C.

30. The method according to claim 20 , wherein the refrigeration system further includes a rupturing device that is arranged to rupture at when the operating pressure within the refrigeration system reaches a rupture pressure, wherein the processor device is arranged to control operation of the compressor to maintain the refrigeration system operating pressure at a value that is less than the rupture pressure.

31. The method according to claim 20 , wherein the extended rest period lasts for at least 5 minutes.

32. The method according to claim 20 , wherein the extended rest period lasts for at least 8 minutes.

33. The method according to claim 20 , wherein the extended rest period lasts for at least 10 minutes.