Weishaupt premix burners achieve NOx emissions below 30 mg/kWh.

The principle: Premixing followed by surface-stabilised combustion has been state of the art for many years in small condensing boilers. Further development was undertaken by Weishaupt to extend the availability of this technology to higher ratings. Premix Low NOx (PLN) burners with NOx emissions below 30 mg/kWh are the result of this work.

New mixing assembly: Stabilised surface combustion relies on an homogeneous gas / air mixture. For that reason, a completely new mixing assembly was developed for the PLN-version burners. A key feature is the separated gas and air feeds, with the two media not being brought together before the burner tube. There, a uniform mix is produced from the gas flowing out through the distributor and the combustion air that has been set in rotation by the swirl plate.

Combustion: The gas / air mix, which is under pressure, permeates the microweave alloy mat and combusts at its surface. The flame carpet thereby created has flame temperatures below 1200 °C and so the formation of thermal NOx is inhibited. NOx emission levels below 30 mg/kWh are now also a reality for medium-capacity burners.

Versatility: One substantial benefit of this technology is to be found in the combustion chamber requirements. These can be considerably smaller than those found in typical boilers.

Digital combustion management: Weishaupt’s PLN-version premix burners also have similar turndowns to their forced-draught stablemates. The electronic compound regulation provided by the W-FM 50, W-FM 100 and W-FM 200 combustion managers can achieve turndown ratios of 7:1 with these burners.

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