Method for operating a boiler appliance, the boiler appliance comprising: a combustion chamber for combusting a combustible, especially for combusting a gas/air mixture within the combustion chamber; a heat exchanger positioned within the combustion chamber, wherein thermal energy resulting from the combustion of the combustible within the combustion chamber is used to heat water flowing through the heat exchanger; a pump for pumping the water through the heat exchanger, wherein a motor of the pump is driven by a control variable provided by a controller; a temperature sensor for measuring the temperature of the water heated by the heat exchanger, wherein the temperature sensor provides a temperature signal to the controller; wherein a feedback signal being indicative about a water flow rate, the water flow rate being provided by the pump and the temperature signal provided by the temperature sensor are both used to determine if the water flow rate through the heat exchanger is sufficient or insufficient, wherein the combustion of the combustible is allowed when a sufficient water flow rate is determined and the combustion of the combustible is not allowed when an insufficient water flow rate is determined; characterized in that the feedback signal is provided by the motor of the pump, wherein the feedback signal provides information that the motor of the pump is consuming electrical power to the controller and is indicative about a water flow rate provided by the pump; upon request of a heat demand the motor of the pump is started to provide the water flow rate through the heat exchanger; after the motor of the pump has been started the feedback signal provided by the motor of the pump is compared with a first threshold, wherein the ignition of the combustion is only started if the feedback signal provided by the motor of the pump is above the first threshold; after the ignition of the combustion has been started the temperature signal provided by the temperature sensor is compared with a second threshold, wherein the continued combustion is only allowed if the temperature signal provided by the temperature sensor is above the second threshold. a combustion chamber for combusting a combustible, especially for combusting a gas/air mixture within the combustion chamber; a heat exchanger positioned within the combustion chamber, wherein thermal energy resulting from the combustion of the combustible within the combustion chamber is used to heat water flowing through the heat exchanger; a pump for pumping the water through the heat exchanger, wherein a motor of the pump is driven by a control variable provided by a controller; a temperature sensor for measuring the temperature of the water heated by the heat exchanger, wherein the temperature sensor provides a temperature signal to the controller; wherein a feedback signal being indicative about a water flow rate, the water flow rate being provided by the pump and the temperature signal provided by the temperature sensor are both used to determine if the water flow rate through the heat exchanger is sufficient or insufficient, wherein the combustion of the combustible is allowed when a sufficient water flow rate is determined and the combustion of the combustible is not allowed when an insufficient water flow rate is determined; characterized in that the feedback signal is provided by the motor of the pump, wherein the feedback signal provides information that the motor of the pump is consuming electrical power to the controller and is indicative about a water flow rate provided by the pump; upon request of a heat demand the motor of the pump is started to provide the water flow rate through the heat exchanger; after the motor of the pump has been started the feedback signal provided by the motor of the pump is compared with a first threshold, wherein the ignition of the combustion is only started if the feedback signal provided by the motor of the pump is above the first threshold; after the ignition of the combustion has been started the temperature signal provided by the temperature sensor is compared with a second threshold, wherein the continued combustion is only allowed if the temperature signal provided by the temperature sensor is above the second threshold.