HVAC system, a method for operating the HVAC system and a HVAC controller configured for the same

1. A controller for a heating, ventilating and air conditioning (HVAC) system, the controller comprising:

an interface configured to:

receive a comfort temperature set point for an enclosed space, the comfort temperature set point comprising a single set point used for both heating mode and cooling mode operation of the HVAC system; and

receive a sensed temperature for the enclosed space; and

a processor configured to:

operate the HVAC system in a conditioning mode of operation, the conditioning mode of operation being one of: a heating mode and a cooling mode;

after operating the HVAC system in the conditioning mode of operation, determine whether to operate the HVAC system in an opposite conditioning mode based on a comparison of a total error value to a pre-determined threshold, wherein:

the opposite conditioning mode is the heating mode if the conditioning mode of operation is the cooling mode and the opposite conditioning mode is the cooling mode if the conditioning mode of operation is the heating mode;

the total error value is calculated as a sum of a proportional error and an integral error;

the proportional error is calculated based on a present value of a temperature error scaled according to a proportional gain value, the present value of the temperature error being calculated as a difference between the comfort temperature and the sensed temperature; and

the integral error is determined based on a change counter, wherein the integral error is set to zero when the change counter is below a change threshold, wherein the change counter is incremented or decremented according to a slope of the sensed temperature of the enclosed space over time;

in response to determining that the total error value exceeds the pre-determined threshold, operate the HVAC system in the opposite conditioning mode; and

in response to determining that the total error value does not exceed the pre-determined threshold, operate the HVAC system in a coasting mode.

2. The controller as recited in claim 1 , wherein:

the integral error is calculated based on past values of temperature error scaled according to an integral gain value when the change counter exceeds the change threshold.

3. The controller as recited in claim 2 , wherein the processor is configured to adjust one or both of the proportional gain value and the integral gain value in response to receiving a change of the comfort temperature set point.

4. The controller as recited in claim 1 , wherein the processor is further configured to:

operate the HVAC system based on the comfort temperature set point when the enclosed space is determined to be in an occupied state; and

operate the HVAC system based on a maximum unoccupied temperature and a minimum unoccupied temperature when the enclosed space is determined to be in an unoccupied state.

5. The controller as recited in claim 1 , wherein the processor is further configured to determine that the HVAC system has been in the coasting mode for a maximum coasting time.

6. The controller as recited in claim 5 , wherein:

the processor initiates either the heating mode or the cooling mode in response to determining that the HVAC system has been in the coasting mode for the maximum coasting time.

7. The controller of claim 1 , wherein the pre-determined threshold is the proportional gain value multiplied by a mode change temperature.

8. The controller of claim 1 , wherein the change counter is incremented or decremented based on a comparison of the slope of the sensed temperature of the enclosed space over time to a slope threshold.

9. A method for controlling a heating, ventilating and air conditioning (HVAC) system, the method comprising:

receiving a comfort temperature set point for an enclosed space, the comfort temperature set point comprising a single set point used for both heating and cooling mode operation of the HVAC system;

receiving a sensed temperature for the enclosed space;

operating the HVAC system in a conditioning mode of operation, the conditioning mode of operation being one of: a heating mode and a cooling mode;

after operating the HVAC system in the conditioning mode of operation, determining whether to operate the HVAC system in an opposite conditioning mode based on a comparison of a total error value to a pre-determined threshold, wherein;

the opposite conditioning mode is the heating mode if the conditioning mode of operation is the cooling mode and the opposite conditioning mode is the cooling mode if the conditioning mode of operation is the heating mode;

the total error value is calculated as a sum of a proportional error and an integral error;

the proportional error is calculated based on a present value of a temperature error scaled according to a proportional gain value, the present value of the temperature error being calculated as a difference between the comfort temperature and the sensed temperature; and

the integral error is determined based on a change counter, wherein the integral error is set to zero when the change counter is below a change threshold, wherein the change counter is incremented or decremented based on a comparison of a slope of the sensed temperature of the enclosed space over time to a slope threshold;

in response to determining that the total error value exceeds the pre-determined threshold, operate the HVAC system in the opposite conditioning mode; and

in response to determining that the total error value does not exceed the pre-determined threshold, operate the HVAC system in a coasting mode.

10. The method of claim 9 , wherein:

the integral error is calculated based on past values of temperature error scaled according to an integral gain value when the change counter exceeds the change threshold.

11. The method of claim 10 , further comprising adjusting one or both of the proportional gain value and the integral gain value in response to receiving a change of the comfort temperature set point.

12. The method of claim 9 , further comprising:

operating the HVAC system based on the comfort temperature set point when the enclosed space is determined to be in an occupied state; and

operating the HVAC system based on a maximum unoccupied temperature and a minimum unoccupied temperature when the enclosed space is determined to be in an unoccupied state.

13. The method of claim 9 , further comprising:

determining that the HVAC system has been in the coasting mode for a maximum coasting time; and

initiating the heating mode or the cooling mode in response to determining that the HVAC system has been in the coasting mode for a maximum coasting time.

14. A heating, ventilating and air conditioning (HVAC) system operable to condition an enclosed space, the HVAC system comprising:

one or more heating components operable to heat to heat the enclosed space when the HVAC system is in a heating mode;

one or more cooling components operable to cool the enclosed space when the HVAC system is in a cooling mode;

one or more temperature sensors, the temperature sensors operable to sense temperature data associated with the enclosed space; and

a controller operable to:

receive a comfort temperature set point for the enclosed space, the comfort temperature set point comprising a single set point used for both the heating mode and the cooling mode operation of the HVAC system; and

receive a sensed temperature from the temperature sensors; and

operate the HVAC system in a conditioning mode of operation, the conditioning mode of operation being one of: a heating mode and a cooling mode;

after operating the HVAC system in the selected conditioning mode, determine whether to operate the HVAC system in an opposite conditioning mode based on a comparison of a total error value to a pre-determined threshold, wherein:

the opposite conditioning mode is the heating mode if the conditioning mode of operation is the cooling mode and the opposite conditioning mode is the cooling mode if the conditioning mode of operation is the heating mode;

the total error value is calculated as a sum of a proportional error and an integral error;

the proportional error is calculated based on a present value of a temperature error scaled according to a proportional gain value, the present value of the temperature error being calculated as a difference between the comfort temperature and the sensed temperature;

the integral error is determined based on a change counter, wherein the integral error is set to zero when the change counter is below a change threshold, wherein the change counter is incremented or decremented according to slope of the sensed temperature of the enclosed space over time;

in response to determining that the total error value exceeds the pre-determined threshold, operate the HVAC system in the opposite conditioning mode;

in response to determining that the total error value does not exceed the pre-determined threshold, operate the HVAC system in a coasting mode.

15. The HVAC system of claim 14 , wherein:

the integral error is calculated based on past values of temperature error scaled according to an integral gain value when the change counter exceeds the change threshold.

16. The HVAC system of claim 15 , wherein the controller is configured to adjust one or both of the proportional gain value and the integral gain value in response to receiving a change of the comfort temperature set point.

17. The HV AC system of claim 15 , wherein the change counter is incremented or decremented based on a comparison of the slope of the sensed temperature of the enclosed space over time to a slope threshold.