Gas valve and method of control

A gas valve unit comprising:

• a stepper motor that generates an incremental output in response to an input signal to the stepper motor;
• a valve member that is movable in response to the incremental output for controllably displacing a valve element relative to a valve opening to adjust a gas flow rate therethrough, where the input signal to the stepper motor controls the extent of movement of the valve member relative to the valve opening;
• a sensor that provides an output indicative of a gas pressure at an outlet of the gas valve unit;
• a setting device that provides an input for selection of at least one opening flow rate profile that is a function describing desired outlet pressure over a time sequence associated with a valve opening phase for establishing combustion, the opening flow rate profile configured for use in controlling the level of gas flow for initially establishing combustion in a heating apparatus;
• and
• a valve controller in communication with the sensor and the setting device, the valve controller being configured to control the input signal to the stepper motor to control movement of the valve element for controlling the gas flow rate through the outlet, the valve controller being configured to control the input signal to the stepper motor based in part on the sensor output, to control the valve element and thereby control the gas flow rate at the outlet to provide outlet pressure over time in accordance with the opening flow rate profile selected by the setting device.