Abstract: The invention relates to a method for operating a gas heater, in particular a gas heater for providing central heating and/or for providing domestic hot water, in particular a gas boiler, in particular a condensing boiler, wherein the method comprises the following steps: supplying a gas and a fuel gas into a mixing chamber of the gas heater and supplying a mixed gas from the mixing chamber to a burner of the gas heater, measure the differential pressure per unit time and/or provide a sensor signal to the control unit for determining a gas quantity, defined by a volume per unit time or a mass per unit time, before the gas is supplied to the mixing chamber, measure the differential pressure per unit time and/or provide a sensor signal to the control unit for determining a fuel gas quantity, defined by a volume per unit time or a mass per unit time, before the fuel gas is supplied to the mixing chamber and determining whether at least one operation condition of the gas heater is fulfilled based on the determine

Abstract: A gas heater includes a premix burner, a supply channel for supplying a mixture of a gaseous fuel and air to the burner, and a check valve placed in the supply channel upstream of the burner. The check valve includes a moveable valve body having a first end position in which the check valve is opened and a second end position in which the check valve is closed. In a first pressure condition in which a pressure upstream is higher than a pressure downstream, the valve body is urged to the first end position. In a second pressure condition in which the pressure upstream is lower than the pressure downstream the valve body is urged to the second end position. After closure of the check valve the check valve remains closed for a delay time.

Abstract: A method for operating a premix gas burner wherein an air flow rate and/or a fuel gas flow rate are controlled so as to generate heat with the premix burner in accordance with a heat demand related value. The fuel gas comprises hydrogen and the method further provides a desired air excess factor relation of the air/fuel gas mixture which defines the relation between a desired air excess factor and an input variable like the heat demand related value, an air flow rate related value, or a fuel gas flow rate related value. The desired air excess factor is not a constant factor but varies for different input variable values. The fuel gas flow rate and/or the air flow rate are controlled such that an actual air excess factor converges towards the desired air excess factor while meeting the heat demand.

Abstract: A gas heater includes a premix burner, a supply channel for supplying a mixture of a gaseous fuel and air to the burner, and a check valve placed in the supply channel upstream of the burner. The check valve includes a moveable valve body having a first end position in which the check valve is opened and a second end position in which the check valve is closed. In a first pressure condition in which a pressure upstream is higher than a pressure downstream, the valve body is urged to the first end position. In a second pressure condition in which the pressure upstream is lower than the pressure downstream the valve body is urged to the second end position. After closure of the check valve the check valve remains closed for a delay time.