Automatic switching refrigeration system

• US 6,679,074 B2
• Filed: 07/29/2002
• Issued: 01/20/2004
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: Thermo King Corporation (Trane Technologies plc)
• Original Assignee: Thermo King Corporation (Trane Technologies plc)
• Inventors: Hanson, Jay Lowell
• Primary Examiner(s): NORMAN, MARC E
• Application Number:
  US10/207,553
• Publication Number:
  US 20030024256A1
• Time in Patent Office: 540 Days
• Field of Search: 621/60, 621/59, 622/285, 622/29, 622/09
• US Class Current: 62/160
• CPC Class Codes: F25B 27/00 Machines, plants or systems, using particular sources of energy F25B30/06 takes precedence
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 47/022 hot gas defrosting
• CPC Class Codes: F25D 17/06 by forced circulation
• CPC Class Codes: F25D 29/003 for movable devices

Abstract

A method of operating a refrigeration system having a discharge port that guides conditioned air from the system to a conditioned space and a return port that guides air from the conditioned space back to the system. The method comprises providing a first control algorithm and second control algorithm for controlling the system. The first control algorithm is a function of the air temperature at the discharge port, and the second control algorithm is a function of the air temperature at the return port. The method further comprises operating the system using the first control algorithm when a first condition is met, operating the system using the second control algorithm when a second condition is met, and automatically switching between the first control algorithm and the second control algorithm depending on the status of the first and second conditions.

Claims

1. A method of operating a refrigeration system designed to condition a conditioned space to a set point temperature, the system having a discharge port that guides conditioned air from the system to the conditioned space and a return port that guides air from the conditioned space back to the system, the method comprising:

providing a first control algorithm and second control algorithm for controlling the system, the first control algorithm being a function of the air temperature at the discharge port, and the second control algorithm being a function of the air temperature at the return port;

operating the system using the first control algorithm when a first condition is met, and operating the system using the second control algorithm when a second condition is met; and

automatically switching between the first control algorithm and the second control algorithm depending on the status of the first condition and the second condition.

2. The method of claim 1 further comprising measuring a temperature of ambient air outside of the conditioned space, wherein the first and second conditions are a function of the ambient air temperature.

3. The method of claim 2 wherein the first condition comprises the ambient temperature being greater than or equal to the set point.

4. The method of claim 2 wherein the second condition comprises the ambient temperature being less than the set point.

5. The method of claim 1 wherein operating the system using the first control algorithm when a first condition is met, and operating the system using the second control algorithm when a second condition is met includes:

measuring a temperature of ambient air outside of the conditioned space;

comparing the ambient air temperature to the set point;

controlling the system utilizing the first control algorithm if the ambient air temperature is greater than or equal to the set point; and

controlling the system utilizing the second control algorithm if the ambient air temperature is less than the set point.

6. The method of claim 1 wherein the system can operate in a high speed heat mode or a low speed heat modulation mode, and wherein operating the system using the second control algorithm when the second condition is met includes:

operating the system in the high speed heat mode if the return air temperature is more than about 5 degrees below the set point; and

operating the system in the low speed heat modulation mode if the return air temperature is less than about 1.5 degrees above the set point.

7. The method of claim 1 wherein the system can operate in a high speed heat mode, a low speed heat modulation mode, and a timed mode, and wherein operating the system using the second control algorithm when the second condition is met includes:

operating the system in the low speed heat mode if the return air temperature is less than about 1.5 degrees above the set point;

operating the system in the timed mode a predetermined period of time if the return air temperature is more than about 3 degrees below the set point temperature; and

operating the system in the high speed heat mode if the return air temperature is more than about 3 degrees below the set point temperature for the predetermined period of time.

8. The method of claim 1 wherein the system can operate in a low speed cool modulation mode and a low speed cool mode, and wherein operating the system using the first control algorithm when the first condition is met includes:

operating the system in low speed cool mode if the return air temperature is less than about 0.5 degrees below the set point; and

operating the system in low speed cool modulation mode if the return air temperature is less than about 3 degrees above than the set point.

9. The method of claim 1 wherein the system can operate in a low speed cool modulation mode, a high speed cool mode, and a timed mode, and wherein operating the system using the first control algorithm when the first condition is met includes:

operating the system in the low speed cool modulation mode if the discharge air temperature is less than about 5.0 degrees above the set point;

operating the system in the timed mode a predetermined period of time if the discharge air temperature is more than about 5.0 degrees above the set point temperature; and

operating the system in the high speed cool mode if the discharge air temperature is more than about 5.0 degrees above the set point temperature for the predetermined period of time.

10. The method of claim 1 wherein the system can operate in a high speed cool mode or a low speed cool modulation mode, and wherein operating the system using the first control algorithm when a first condition is met includes:

operating the system in the high speed cool mode if the discharge air temperature is more than about 3 degrees above the set point; and

operating the system in the low speed cool modulation mode if the discharge air temperature is less than about 3 degrees above the set point.

11. The method of claim 1 wherein the system can operate in low speed heat mode or low speed cool modulation mode, and wherein the step of controlling the system utilizing the second algorithm includes:

operating the system in low speed heat mode if the return air temperature is less than about 1.5 degrees more than the set point; and

operating the system in low speed cool modulation mode if the return air temperature is greater than about 1.5 degrees more than the set point.

12. A method of operating a refrigeration system designed to condition the air of a conditioned space to a set point, the system having a discharge port that guides conditioned air from the system to the conditioned space and a return port that guides air from the conditioned space back to the system, the system being operable in discharge air control wherein control of the system is a function of the temperature of the air in the discharge port, and the system being operable in return air control wherein control of the system is a function of the temperature of the air in the return port, the method comprising:

operating the system using discharge air control when a first condition is met, and operating the system using return air control when a second condition is met; and

automatically switching between discharge air control and return air control depending on the status of the first condition and the second condition.

13. The method of claim 12 further comprising measuring ambient air temperature of the air outside of the conditioned space, wherein the first and second conditions are a function of the ambient air temperature.

14. The method of claim 13 wherein the first condition comprises the ambient temperature being greater than or equal to the set point.

15. The method of claim 13 wherein the second condition comprises the ambient temperature being less than the set point.

16. The method of claim 12 wherein the operating step comprises:

measuring a temperature of ambient air outside of the conditioned space;

comparing the ambient air temperature to the set point;

controlling the system utilizing discharge air temperature if the ambient air temperature is greater than or equal to the set point; and

controlling the system utilizing return air temperature if the ambient air temperature is less than the set point.

17. The method of claim 12 wherein the system can operate in high speed heat mode or low speed cool modulation mode, and wherein the step of controlling the system utilizing the first algorithm includes:

operating the system in high speed heat mode if the discharge air temperature is less than about 3.0 above the set point; and

operating the system in low speed cool modulation mode if the return air temperature is less than about 3.0 degrees above than the set point.

18. The method of claim 12 wherein the system can operate in low speed cool modulation mode or low speed cool mode, and wherein the step of controlling the system utilizing the second control algorithm includes:

operating the system in low speed cool modulation mode if the return air temperature is less than about 0.5 degrees more than the set point; and

operating the system in low speed cool mode if the return air temperature is greater than about 0.5 degrees more than the set point.

19. The method of claim 12 wherein the system can operate in high speed cool mode or low speed cool modulation mode, and wherein the step of controlling the system utilizing the first algorithm includes:

operating the system in high speed cool mode if the discharge air temperature is greater than about 3 degrees more than the set point; and

operating the system in low speed cool modulation mode if the discharge air temperature is less than about 3 degrees more than the set point.

20. The method of claim 12 wherein the system can operate in low speed heat mode or low speed cool modulation mode, and wherein the step of controlling the system utilizing the second algorithm includes:

operating the system in low speed heat mode if the discharge air temperature is less than about 1 degrees more than the set point; and

operating the system in low speed cool modulation mode if the discharge air temperature is greater than about 1 degrees more than the set point.

21. A refrigeration system comprising:

heat exchanger having an air discharge port and an air return port;

a first sensor positioned in the discharge port;

a second sensor positioned in the return port;

a controller in electrical communication with the first sensor and the second sensor, the controller alternately using a first control algorithm to control the system when a first condition is met and using a second control algorithm to control the system when a second condition is met, the first control algorithm being a function of the air temperature at the discharge port, the second control algorithm being a function of the air temperature at the return port.

22. The refrigeration system of claim 21 wherein the discharge port and the air return port are in thermal communication with an air conditioned space and further comprising a third sensor positioned outside the heat exchanger, the first and second conditions being a function of the ambient air temperature.

23. The refrigeration system of claim 22 wherein the first condition comprises the ambient temperature being greater than or equal to the set point.

24. The refrigeration system of claim 22 wherein the second condition comprises the ambient temperature being less than the set point.