System and method of controlling a variable-capacity compressor

1. A climate-control system comprising a variable-capacity compressor unit and a control module controlling the compressor unit, the compressor unit operable at a first capacity and at a second capacity that is different than the first capacity, the control module configured to switch the compressor unit between the first capacity and the second capacity during a demand period based on an outdoor-air-temperature slope, and a previous runtime of the compressor unit at the second capacity during a previous demand period.

2. The climate-control system of claim 1 , wherein the control module is configured to switch the compressor unit between the first capacity and the second capacity based a current outdoor air temperature.

3. The climate-control system of claim 1 , wherein the control module determines which of a first range, a second range, a third range, and a fourth range the outdoor-air-temperature slope is within.

4. The climate-control system of claim 3 , wherein the control module sets a runtime of the compressor unit in the first capacity according to one of four columns in a lookup table based on which one of the first, second, third and fourth ranges the outdoor-air-temperature slope is within.

5. The climate-control system of claim 4 , wherein the first range includes an outdoor-air-temperature slope of zero, the second range corresponds to a positive outdoor-air-temperature slope, the third range corresponds to a negative outdoor-air-temperature slope, and the fourth range corresponds to an extreme negative outdoor-air-temperature slope.

6. The climate-control system of claim 1 , wherein the control module accounts for relative humidity based on the outdoor-air-temperature slope.

7. The climate-control system of claim 1 , wherein the control module accounts for a thermal load of a building to be heated or cooled by the climate-control system based on the outdoor-air-temperature slope.

8. The climate-control system of claim 1 , further comprising an indoor blower forcing air over an indoor heat exchanger, the indoor blower having a speed setting determined based on a region in which the climate-control system is installed.

9. The climate-control system of claim 1 , wherein the control module sets system operating parameters based on a region in which the climate-control system is installed, wherein the system operating parameters include one or more of a runtime of the compressor unit at the second capacity, a runtime of the compressor unit at the first capacity, and a fan speed.

10. The climate-control system of claim 9 , wherein the control module selects a region based on a comparison of outdoor-air-temperature values and outdoor-relative-humidity values with predetermined ranges of outdoor-air-temperature and outdoor-relative-humidity values.

11. The climate-control system of claim 9 , wherein the control module selects a region based on a comparison of user-selected indoor temperature setpoints with predetermined ranges of indoor temperature setpoints.

12. The climate-control system of claim 1 , wherein the second capacity is higher than the first capacity.

13. A climate-control system comprising:

a variable-capacity compressor unit operable at a first capacity and at a second capacity that is different than the first capacity; and

a control module configured to receive outdoor-air-temperature data and determine an outdoor-air-temperature slope, and wherein the control module is configured to switch the variable-capacity compressor unit between the first capacity and the second capacity during a demand period based on the outdoor-air-temperature slope.

14. The climate-control system of claim 13 , wherein the control module switches the variable-capacity compressor unit between the first capacity and the second capacity during the demand period based on a current outdoor air temperature and a previous runtime of the compressor unit at the second capacity during a previous demand period.

15. The climate-control system of claim 13 , wherein the control module is configured to set at least one system operating parameter based on a region in which the climate-control system is installed, wherein the at least one system operating parameter includes at least one of a runtime of the variable-capacity compressor unit at the first capacity, a runtime of the variable-capacity compressor unit at the second capacity, and a fan speed.

16. The climate-control system of claim 15 , wherein the control module sets the at least one system operating parameter based on a time of day.

17. The climate-control system of claim 16 , wherein the control module approximates the time of day based on the outdoor-air-temperature slope.

18. The climate-control system of claim 15 , wherein the control module determines which of a first range, a second range, a third range, and a fourth range the outdoor-air-temperature slope is within.

19. The climate-control system of claim 18 , wherein the control module sets a runtime of the variable-capacity compressor unit at the first capacity according to one of four columns in a lookup table based on which one of the first, second, third and fourth ranges the outdoor-air-temperature slope is within.

20. The climate-control system of claim 19 , wherein the first range includes an outdoor-air-temperature slope of zero, the second range corresponds to a positive outdoor-air-temperature slope, the third range corresponds to a negative outdoor-air-temperature slope, and the fourth range corresponds to an extreme negative outdoor-air-temperature slope.

21. The climate-control system of claim 20 , wherein the control module accounts for relative humidity based on the outdoor-air-temperature slope.

22. The climate-control system of claim 21 , wherein the control module accounts for a thermal load of a building to be heated or cooled by the climate-control system based on the outdoor-air-temperature slope.

23. The climate-control system of claim 13 , wherein the second capacity is higher than the first capacity.