Gas/air mixing device of a gas burner

A gas/air mixing device of a gas burner, the gas/air mixing device being configured to mix gas and air to provide a gas/air mixture, wherein the gas/air device includes:

• a mixer housing including a mounting flange configured to mount the gas/air mixing device to a fan housing of a fan of the gas burner in such a way that a sealing surface of the mounting flange is in contact with a sealing surface of the fan housing,
• wherein the sealing surface of the mounting flange has grooves being configured to accommodate sealing elements, namely a first groove with a first radius to accommodate a first sealing element, and a second groove with a second radius being different from the first radius to accommodate a second sealing element, or
• wherein the sealing surface of the fan housing has a groove to accommodate a sealing element, the groove comprising at least one of a first groove with a first radius to accommodate a first sealing element or a second groove with a second radius being different from the first radius to accommodate a second sealing element,
• the mixer housing provides an inlet opening for the air,
• the mixer housing provides an inlet opening for the gas,
• the mixer housing provides an outlet opening for the gas/air mixture,
• the mounting flange of the mixer housing, namely the sealing surface of the mounting flange, surrounds the outlet opening of the mixer housing, and
• the mounting flange of the mixer housing has protrusions with sections being configured to accommodate mounting screws, the seconds comprising:
• a first section being configured to provide first through holes for mounting screws used when one of the first sealing element and second sealing element shall be used to seal the mixer housing versus the fan housing, and
• a second section being configured to provide second through holes for mounting screws used when the other one of the first sealing element and second sealing element shall be used to seal the mixer housing versus the fan housing.