Method and controller for operating a gas burner appliance and gas burner appliance

A method for operating a gas burner appliance, the gas burner appliance comprising:

• a combustion chamber in which a defined gas/air mixture is combusted after combustion has been started in connection with a burner start,
• a mixing device to provide the gas/air mixture by mixing an air flow provided by an air duct with a gas flow provided by a gas duct,
• a fan to provide the air flow or the flow of the gas/air mixture, wherein a fan speed of the fan depends on a burner-load of the gas burner appliance,
• a gas safety valve unit assigned to the gas duct to open or close the gas duct,
• a gas flow modulator or a gas flow regulator assigned to the gas duct to keep a mixing ratio of gas and air of the defined gas/air mixture constant over the modulation range of the gas burner appliance,
• an absolute pressure sensor positioned between the gas safety valve unit and the mixing device,
• wherein the gas burner appliance is operated to determine the air flow resistance of the gas burner appliance by executing the following steps before combustion becomes started in connection with a burner start:
• measuring a first absolute pressure by the absolute pressure sensor is closed and when the fan is stopped,
• measuring a second absolute pressure by the absolute pressure sensor when the gas safety valve unit is closed and when the fan is running,
• determining a pressure difference between the first absolute pressure and the second absolute pressure,
• determining on basis of the pressure difference the air flow resistance of the gas burner appliance.