System and method of controlling a variable-capacity compressor

1. A system comprising:

a variable-capacity compressor operable in a first capacity mode and in a second capacity mode that is higher than the first capacity mode; and

a controller configured to switch the variable-capacity compressor between the first capacity mode and the second capacity mode based on a demand signal from a thermostat and an indoor relative humidity sensed by an indoor relative humidity sensor,

wherein the controller determines whether the indoor relative humidity is greater than a predetermined humidity and operates the variable-capacity compressor in the second capacity mode in response to receiving the demand signal from the thermostat and the indoor relative humidity exceeding the predetermined humidity; and

wherein the controller is further configured to determine a number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within a predetermined period of time and to operate the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within the predetermined period of time being less than a predetermined threshold.

2. The system of claim 1 , wherein the thermostat includes the indoor relative humidity sensor and communicates indoor relative humidity data indicating the indoor relative humidity to the controller.

3. The system of claim 1 , wherein the controller is further configured to set a runtime of the variable-capacity compressor in the second capacity mode according to the indoor relative humidity.

4. The system of claim 1 , wherein the thermostat is configured to measure an air temperature, receive a setpoint temperature, and generate the demand signal based on a difference between the air temperature and the setpoint temperature.

5. The system of claim 1 , wherein the controller is further configured to receive outdoor-air-temperature data corresponding to an outdoor-air-temperature from an outdoor-air-temperature sensor and to set a runtime of the variable-capacity compressor in the second capacity mode according to the outdoor-air-temperature.

6. The system of claim 1 , wherein the controller is further configured to:

determine an average runtime of the previous consecutive operating cycles; and

operate the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold and the average runtime of the previous consecutive operating cycles being greater than or equal to a predetermined value.

7. The system of claim 1 , wherein the controller is further configured to:

determine an average runtime of the previous consecutive operating cycles; and

operate the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold, the average runtime of the previous consecutive operating cycles being less than or equal to a predetermined value, and the indoor relative humidity being less than or equal to the predetermined humidity.

8. The system of claim 1 , wherein the controller is further configured to:

determine an average runtime of the previous consecutive operating cycles; and

operate the variable-capacity compressor in the second capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold, the average runtime of the previous consecutive operating cycles being less than or equal to a predetermined value, and the indoor relative humidity being greater than or equal to the predetermined humidity.

9. A method of controlling a variable-capacity compressor operable in a first capacity mode and in a second capacity mode that is higher than the first capacity mode, the method comprising:

receiving, with a controller, a demand signal from a thermostat;

receiving, with the controller, an indoor relative humidity sensed by an indoor relative humidity sensor;

determining, with the controller, whether the indoor relative humidity is greater than a predetermined humidity;

operating, with the controller, the variable-capacity compressor in the second capacity mode in response to receiving the demand signal from the thermostat and to the indoor relative humidity exceeding the predetermined humidity;

determining, with the controller, a number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within a predetermined period of time; and

operating, with the controller, the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within the predetermined period of time being less than a predetermined threshold.

10. The method of claim 9 , wherein the thermostat includes the indoor relative humidity sensor and communicates indoor relative humidity data indicating the indoor relative humidity to the controller.

11. The method of claim 9 , further comprising:

setting, with the controller, a runtime of the variable-capacity compressor in the second capacity mode according to the indoor relative humidity.

12. The method of claim 9 , wherein the thermostat is configured to measure an air temperature, receive a setpoint temperature, and generate the demand signal based on a difference between the air temperature and the setpoint temperature.

13. The method of claim 9 , further comprising:

receiving, with the controller, outdoor-air-temperature data corresponding to an outdoor-air-temperature from an outdoor-air-temperature sensor; and

setting, with the controller, a runtime of the variable-capacity compressor in the second capacity mode according to the outdoor-air-temperature.

14. The method of claim 9 , further comprising:

determining, with the controller, an average runtime of the previous consecutive operating cycles; and

operating, with the controller, the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold and the average runtime of the previous consecutive operating cycles being greater than or equal to a predetermined value.

15. The method of claim 9 , further comprising:

determining, with the controller, an average runtime of the previous consecutive operating cycles; and

operating, with the controller, the variable-capacity compressor in the first capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold, the average runtime of the previous consecutive operating cycles being less than or equal to a predetermined value, and the indoor relative humidity being less than or equal to the predetermined humidity.

16. The method of claim 9 , further comprising:

determining, with the controller, an average runtime of the previous consecutive operating cycles; and

operating, with the controller, the variable-capacity compressor in the second capacity mode in response to the number of previous consecutive operating cycles being greater than or equal to the predetermined threshold, the average runtime of the previous consecutive operating cycles being less than or equal to a predetermined value, and the indoor relative humidity being greater than or equal to the predetermined humidity.

17. A system comprising:

a variable-capacity compressor operable in a first capacity mode and in a second capacity mode that is higher than the first capacity mode; and

a controller configured to determine whether to bypass the first capacity mode and initially operate the variable-capacity compressor in the second capacity mode during an operation cycle based on a demand signal from a thermostat, an indoor relative humidity sensed by an indoor humidity sensor, and a short cycle flag that is set and cleared by the controller;

wherein the controller is configured to set the short cycle flag when the first capacity mode is bypassed, clear the short cycle flag when the first capacity mode is not bypassed, determine whether the indoor relative humidity is greater than a predetermined humidity, and bypass the first capacity mode to operate the variable-capacity compressor in the second capacity mode in response to receiving the demand signal from the thermostat, the short cycle flag being set, and the indoor relative humidity exceeding the predetermined humidity; and

wherein the controller is further configured to determine a number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within a predetermined period of time and to not bypass the first capacity mode in response to the short cycle flag not being set and the number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within the predetermined period of time being less than a predetermined threshold.

18. The system of claim 17 , wherein the controller is further configured to determine an average compressor runtime during the previous consecutive operating cycles of the variable-capacity compressor and to not bypass the first capacity mode in response to (i) the short cycle flag not being set, (ii) the number of previous consecutive operating cycles of the variable-capacity compressor in the first capacity mode within the predetermined period of time being greater than the predetermined threshold, and (iii) the average compressor runtime during the previous consecutive operating cycles of the variable-capacity compressor being less than a predetermined value.

19. The system of claim 17 , wherein the controller is configured to set a runtime of the variable-capacity compressor in the second capacity mode according to the indoor relative humidity.

20. The system of claim 17 , wherein the thermostat is configured to measure an air temperature, receive a setpoint temperature, and generate the demand signal based on a difference between the air temperature and the setpoint temperature.

21. The system of claim 17 , wherein the controller is further configured to receive outdoor-air-temperature data corresponding to an outdoor-air-temperature from an outdoor-air-temperature sensor and to set a runtime of the variable-capacity compressor in the second capacity mode according to the outdoor-air-temperature.