Method and apparatus for using single-stage thermostat to control two-stage cooling system

• US 6,370,894 B1
• Filed: 03/08/2001
• Issued: 04/16/2002
• Est. Priority Date: 03/08/2001
• Status: Active Grant

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Kiningham, Paul, Tumbusch, Dave, Thompson, Kevin D.
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US09/802,578
• Time in Patent Office: 404 Days
• Field of Search: 622/31, 621/58, 621/75, 236/1.EA
• US Class Current: 62/158
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: G05D 23/1912 whose output amplitude can take more than two discrete values

Abstract

When a single-stage thermostat is appropriately connected to a two-stage cooling system, a microprocessor control activates low and high stages of cooling based on preset parameters. The cooling load requirement is determined and compared to the maximum load requirement that can be satisfied in low-stage cooling mode and the minimum load requirement which can be satisfied in high-stage cooling mode. The desired low-stage cooling time limit is then determined for the next cycle. After the first cycle, the desired low-stage cooling time limit may be equal to zero in which case the next cycle is spent in high-stage cooling mode, or, if greater than zero, the next cycle runs in low-stage cooling mode up to the desired low-stage cooling time limit, with an additional high-stage cooling mode run if the thermostat is not satisfied within the desired time.

Claims

1. A method for selectively providing a low cooling mode and a high cooling mode of a cooling cycle in an air conditioning unit as a function of a previous cooling cycle, comprising the steps of:

storing a previous duration of operation of a low cooling mode and a previous duration of operation of a high cooling mode of a previous cooling cycle;

determining an existence of a cooling load to be satisfied;

recalling the stored duration of the previous low cooling mode;

providing a low cooling mode for a selected first time period dependent upon the stored duration of the previous low cooling mode; and

terminating the low cooling mode if the cooling load is satisfied during the selected first time period.

2. The method of claim 1, further comprising the steps of:

determining whether continuation of the cooling load still exists after the selected first time period of the low cooling mode;

providing a high cooling mode if the cooling load continues until the cooling load is satisfied; and

terminating the high cooling mode when the cooling load is satisfied.

3. The method of claim 1 wherein the selected first time period of the low cooling mode is greater than the stored duration of the previous low cooling mode when the stored duration of the previous high cooling mode is less than a predetermined amount of time.

4. The method of claim 1 wherein the selected first time period of the low cooling mode is less than the stored duration of the previous low cooling mode when the stored duration of the previous high cooling mode is greater than a predetermined amount of time.

5. The method of claim 1 wherein determination of the existing cooling load is performed by a single-stage thermostat.

6. The method of claim 1, wherein said air conditioning unit includes an air conditioning relay, said air conditioning relay is disabled, and determination of the existing cooling load is performed by a two-stage thermostat.

7. A method for selectively providing a low cooling mode and a high cooling mode of a cooling cycle in an air conditioning unit as a function of a previous cooling cycle, comprising the steps of:

storing the duration of a previous cooling cycle;

determining the existence of a cooling load to be satisfied;

recalling the stored duration of the previous cooling cycle;

providing a low cooling mode for a selected first time period dependent upon the time duration of the previous cooling cycle and the determination of the existing cooling load to be satisfied; and

terminating the low cooling mode if the cooling load is satisfied during the selected first time period.

8. The method of claim 7, further comprising the steps of:

determining whether continuation of the cooling load still exists after the selected first time period of the low cooling mode;

providing a high cooling mode if the cooling load continues until the cooling load is satisfied; and

terminating the high cooling mode when the cooling load is satisfied.

9. The method of claim 7 wherein determination of the existing cooling load is performed by a single-stage thermostat.

10. The method of claim 7, further comprising the step of:

storing a previous time period of operation of a low cooling mode and a previous time period of operation of a high cooling mode of the previous cooling cycle;

wherein the step of recalling includes recalling the stored time period of the previous high cooling mode; and

wherein the step of providing the low cooling mode is further dependent upon the stored time period of the previous high cooling mode.

11. The method of claim 10, further comprising the steps of:

determining whether continuation of the cooling load still exists after the selected first time period of the low cooling mode;

providing a high cooling mode if the cooling load continues until the cooling load is satisfied; and

terminating the high cooling mode when the cooling load is satisfied.

12. An adaptive control system for providing a low cooling mode and a high cooling mode of a cooling cycle in an air conditioning unit as a function of a previous cooling cycle, comprising:

means for storing a previous duration of operation of a low cooling mode and a previous duration of operation of a high cooling mode of a previous cooling cycle;

means for determining the existence of a cooling load to be satisfied;

means for recalling the stored duration of the previous low cooling mode;

means for providing a low cooling mode for a selected first time period dependent upon the stored duration of the previous low cooling mode; and

means for terminating the low cooling mode if the cooling load is satisfied during the selected first time period.

13. The system of claim 12, wherein:

the determining means determines whether continuation of the cooling load still exists after the selected first time period of the low cooling mode;

the providing means further provides a high cooling mode if the cooling load continues until the cooling load is satisfied; and

the terminating means terminates the high cooling mode when the cooling load is satisfied.

14. The system of claim 12 wherein:

the storing means further stores the time at which the previous cooling cycle ended;

the recalling means further recalls the previous cooling cycle end time; and

the providing means provides the low cooling mode dependent upon the time duration of the previous cooling cycle and the determination of the existing cooling load to be satisfied.

15. The system of claim 12 wherein the determining means is a single-stage thermostat.

16. An adaptive control system for providing a low cooling mode and a high cooling mode of a cooling cycle in a furnace as a function of a previous cooling cycle, comprising:

means for storing the duration of a previous cooling cycle;

means for determining the existence of a cooling load to be satisfied;

means for recalling the stored duration of the previous cooling cycle;

means for providing a low cooling mode for a selected first time period dependent upon the duration of the previous cooling cycle and the determination of the existing cooling load to be satisfied; and

means for terminating the low cooling mode if the cooling load is satisfied during the selected first time period.

17. The system of claim 16 wherein:

the determining means determines whether continuation of the cooling load still exists after the selected first time period of the low cooling mode;

the providing means further provides a high cooling mode if the cooling load continues until the cooling load is satisfied; and

the terminating means terminates the high cooling mode when the cooling load is satisfied.

18. The system of claim 16 wherein the determining means is a single-stage thermostat.

19. The system of claim 16, wherein said furnace unit includes an air conditioning relay, said air conditioning relay is disabled, and determination of the existing cooling load is performed by a two-stage thermostat.

20. A method for providing a low cooling mode and a high cooling mode of a cooling cycle in a current cycle of an air conditioner unit as a function of the previous cooling cycle wherein the current cooling cycle is a function exclusively of time run in the low cooling mode and time run in the high cooling mode of said previous cooling cycle, comprising the steps of:

determining an existence of a cooling load to be satisfied;

running the unit in said low cooling mode for a first time interval that does not exceed a predetermined limit;

running the unit in said high cooling mode for a second time interval until the cooling load is satisfied;

calculating a cooling load requirement as a function of said first time interval and said second time interval; and

predetermining the low cooling mode time limit for a next cycle from the calculated cooling load requirement.

21. The method of claim 20, further comprising the steps of:

determining if the cooling load is satisfied while the unit is operating in low cooling mode;

if the cooling load is satisfied, terminating the low cooling mode; and

if the cooling load is satisfied in low cooling mode, aborting initiation of operation in high cooling mode.

22. The method of claim 20 wherein determining the existence of a cooling load to be satisfied is performed by a single-stage thermostat.

23. The method of claim 20 where the cooling load requirement to satisfy a call for cooling is calculated as CLR=(3×

LCT)+(5×

HCT), where CLR is the cooling load requirement, LCT is the first time interval, in minutes, and HCT is the second interval, in minutes.