Valve position control

1. A method for calibrating a position of a control valve within a gas valve assembly, the method comprising:

initiating a calibration mode in a controller of the gas valve assembly;

once in the calibration mode, the controller is configured to:

move the control valve to a second end stop;

move the control valve from the second end stop to a first end stop while counting a number of steps traveled by a stepper motor driving the control valve;

comparing the counted number of steps traveled from the second end stop to the first end stop to a reference value stored in a memory of the controller;

wherein when the counted number of steps matches the reference value, the controller resets a position counter to an initial value;

wherein when the counted number of steps does not match the reference value, the controller enters a lockout mode and keeps the control valve at the first end stop, and

wherein moving the control valve from the second end stop to the first end stop comprises moving the control valve a full valve stroke of the control valve plus a predetermined clearance margin, wherein the predetermined clearance margin accounts for particular tolerances associated with the gas valve assembly.

2. The method of claim 1 , wherein:

when the control valve is at the first end stop, the control valve is in a fully closed position; and

when the control valve is at the second end stop, the control valve is in a fully open position.

3. The method of claim 1 , wherein when moving the control valve from the second end stop to the first end stop, the controller is configured to initially operate the stepper motor in a higher current mode for a predetermined number of motor steps before operating the stepper motor in an end stop detect mode whereby the control valve reaching the first end stop is detected by a sensed a higher current draw from the stepper motor.

4. The method of claim 1 , wherein the gas valve assembly further comprises a drive train from the stepper motor to the control valve, and wherein the predetermined clearance margin accounts for particular tolerances associated with the drive train.

5. The method of claim 1 , wherein the controller is configured to initiate the calibration mode upon power-up of the gas valve assembly.

6. The method of claim 1 , wherein the gas valve assembly is configured to supply gas to a burner that operates in burner cycles, wherein the controller is configured to initiate the calibration mode at an end of a burner cycle.

7. The method of claim 6 , wherein when the counted number of steps matches the reference value, the controller resets the position counter to the initial value before moving the control valve to a predetermined position between the second end stop and the first end stop by stepping the stepper motor while incrementing the position counter until the position counter reaches a predetermined value.

8. The method of claim 7 , wherein the predetermined position corresponds to an ignition position of the burner.

9. A gas valve assembly for controlling fuel flow to a combustion appliance, the gas valve assembly comprising:

a valve body with an inlet port and an outlet port, and a fluid path extending between the inlet port and the outlet port, the valve body further including a control valve situated in the fluid path between the inlet port and the outlet port;

a drive train coupled to the control valve;

a stepper motor coupled to the drive train;

a controller secured relative to the valve body and in communication with the stepper motor, the controller configured to command the stepper motor to drive the control valve via the drive train between a fully open position, a fully closed position, and a plurality of intermediate positions;

wherein the controller is configured to selectively enter a calibration mode and once in the calibration mode, the controller is configured to:

command the stepper motor to drive the control valve to the fully open position;

once the control valve is in the fully open position, command the stepper motor to drive the control valve from the fully open position to the fully closed position while counting a number of steps traveled by the stepper motor;

comparing the counted number of steps traveled by the stepper motor to a reference value stored in a memory of the controller; and

wherein when the counted number of steps does not match the reference value, the controller is configured to enter a lockout mode and keeps the control valve in the fully closed position, and

wherein moving the control valve from the fully open position to the fully closed position comprises moving the control valve a full stroke plus a predetermined clearance margin, wherein the predetermined clearance margin accounts for particular tolerances associated with the gas valve assembly.

10. The gas valve assembly of claim 9 , wherein the predetermined clearance margin accounts for particular tolerances associated with the drive train.

11. The gas valve assembly of claim 9 , wherein the controller is configured to initiate the calibration mode upon power-up of the gas valve assembly.

12. The gas valve assembly of claim 9 , wherein the combustion appliance includes a burner that operates in burner cycles, wherein the controller is configured to initiate the calibration mode at an end of a burner cycle.

13. The gas valve assembly of claim 12 , wherein when the counted number of steps matches the reference value, the controller is configured to resets a position counter to an initial value before commanding the control valve to a predetermined position between the fully closed position and the fully open position by stepping the stepper motor while incrementing the position counter until the position counter reaches a predetermined value.

14. The gas valve assembly of claim 13 , wherein the predetermined position corresponds to an ignition position of the burner.

15. The gas valve assembly of claim 9 , wherein when moving the control valve from the fully open position to the fully closed position, the controller is configured to initially operate the stepper motor in a higher current mode for a predetermined number of motor steps before operating the stepper motor in an end stop detect mode whereby the control valve reaching the fully closed position is detected by a sensed a higher current draw from the stepper motor.

16. A gas valve assembly for controlling fuel flow to a burner, the gas valve assembly comprising:

a valve body with an inlet port and an outlet port, and a fluid path extending between the inlet port and the outlet port, the valve body further including a control valve situated in the fluid path between the inlet port and the outlet port;

a stepper motor for driving the control valve;

a controller for controlling the stepper motor, the controller configured to command the stepper motor to drive the control valve between a first end stop and a second end stop; wherein the controller is configured to selectively enter a calibration mode and once in the calibration mode, the controller is configured to:

command the stepper motor to drive the control valve to the second end stop;

once the control valve is at the second end stop, command the stepper motor to drive the control valve from the second end stop to the first end stop while counting a number of steps traveled by the stepper motor;

comparing the counted number of steps traveled by the stepper motor to a reference value; and

wherein when the counted number of steps does not match the reference value, the controller is configured to enter a lockout mode and keeps the control valve at the first end stop, and

wherein moving the control valve from the second end stop to the first end stop comprises moving the control valve a full valve stroke of the control valve plus a predetermined clearance margin, wherein the predetermined clearance margin accounts for particular tolerances associated with the gas valve assembly.

17. The gas valve assembly of claim 16 , wherein when the counted number of steps matches the reference value, the controller is configured to reset a position counter to an initial value before moving the control valve to a predetermined position between the second end stop and the first end stop by stepping the stepper motor while incrementing the position counter until the position counter reaches a predetermined value.

18. The gas valve assembly of claim 17 , wherein the predetermined position corresponds to an ignition position of the burner.