Method for detecting a loss of refrigerant charge of a refrigeration system
A method of determining charge loss of a refrigeration system includes the steps of inputting an ambient temperature, a box temperature, and a compressor speed into an electronic controller of the refrigeration system, and calculating a first air side temperature difference across an evaporator by applying an algorithm having a first T-Map representative of normal operating conditions. The controller may then confirm a detection prerequisite is satisfied. Upon confirmation, the controller calculates a second air side temperature difference across the evaporator by applying the algorithm having a second T-Map representative of a loss of refrigerant charge. An action may then be taken from the controller if the first air side temperature difference is less than the second air side temperature difference.
1. A method of determining charge loss of a refrigeration system comprising:
inputting a supply air temperature, a return air temperature, an ambient temperature, a box temperature, and a compressor speed into an electronic controller of the refrigeration system;
measuring a real-time air side temperature difference across an evaporator;
calculating a first air side temperature difference across the evaporator by applying an algorithm having a first T-Map representative of normal operating conditions;
confirming a detection prerequisite is satisfied;
calculating a second air side temperature difference across the evaporator by applying the algorithm having a second T-Map representative of a loss of refrigerant charge;
taking a first action if the real-time air side temperature difference is less than the first air side temperature difference; and
taking a second action if the real-time air side temperature difference is less than the second air side temperature difference.
2. The method set forth in claim 1 further comprising:
inputting an evaporator multi-speed fan speed.
3. The method set forth in claim 1 , wherein the algorithm applies a polynomial.
4. The method set forth in claim 3 , wherein the first and second T-Maps are pre-programmed into the controller and provide a curve fit of a plurality of constants versus compressor speed.
5. The method set forth in claim 4 , wherein the plurality of constants are six constants applied to ambient temperature and box temperature variables as part of the polynomial.
6. The method set forth in claim 1 , wherein the detection prerequisite is a measured compressor speed being greater than a predefined compressor speed.
7. The method set forth in claim 1 , wherein the detection prerequisite is the first air side temperature difference being greater than a predefined temperature difference.
8. The method set forth in claim 1 , wherein the detection prerequisite is that the first air side temperature difference is determined after a predefined time span from initial system startup and initial pulldown.
9. The method set forth in claim 1 , wherein the detection prerequisite is one of a plurality of detection prerequisites and at least includes a measured compressor speed being greater than a predefined compressor speed, the first air side temperature difference being greater than a predefined temperature difference, and the first air side temperature difference is determined after a predefined time span from initial system startup and initial pulldown.
10. The method set forth in claim 1 , wherein the first and second T-Maps are representative of evaporator air side temperature difference versus ambient temperature, box temperature, compressor speed and refrigerant charge.
11. The method set forth in claim 1 , wherein the refrigeration system is a transcritical refrigeration system.
12. The method set forth in claim 1 further comprising:
inputting an evaporator variable speed fan speed.
13. A refrigeration system comprising:
an electronic controller including,
pre-programmed first and second T-Maps both representative of evaporator air side temperature difference versus ambient temperature, box temperature, compressor speed and refrigerant charge operating conditions, and wherein the first T-Map is representative of normal operating conditions and the second T-Map is representative of a loss of refrigerant charge, and
pre-programmed prerequisites configured to be met prior to initiating an action based on a loss of refrigerant charge; and
wherein the electronic controller is configured to calculate first and second evaporator air side temperatures based on the respective first and second T-maps and initiates an action if the first air side temperature difference is less than the second air side temperature difference.
14. The refrigeration system set forth in claim 13 , wherein the refrigeration system is a transcritical refrigeration system.
15. The refrigeration system set forth in claim 14 , wherein the refrigerant is CO2.