Chimneys have to be RESISTANT TO SOOT FIRE!

In the past there was no need for operation under wet conditions in relation to the connection of fireplaces fired by solid fuels, because the flue gas temperatures of such fireplaces were so high that the water vapor in the chimney did not condensate. Operation under dry conditions was sufficient and normal. Operation under wet conditions was only required for fireplaces fired by oil and gas, which have low flue gas temperatures.

With continuous improvements in energy efficiency, the flue gas temperature in modern-day low-temperature heating systems has come down to such an extent that the water vapor contained in the flue gas turns to condensation. This applies in particular to fireplaces run on a regenerative basis using wood, hogged wood or pellets. The combustion of the solid fuels generates soot which collects in the flue column. Under certain circumstances this can ignite in the flue column – leading to a soot fire, which can be associated with temperatures of up to 1000°C or more.

The chimney system must be capable of withstanding this without damage, in other words without developing cracks. The consequence of cracks would be sooting and the loss of gas tightness – meaning that the chimney would be useless. You will be on the safe side if you use a chimney system with ceramic flue liners of classification W3G.

W3G is the highest classification for chimneys and means the following:

• “W” stands for “wet” (or operation in wet conditions), i.e. insensitive to condensation
• “3” stands for the highest corrosion-resistance to condensation from the combustion of oil, bio-oil, gas, biogas and all solid fuels
• “G” stands for resistance to soot fires, which means that the flue liner is still in perfect condition after a soot fire and is free of cracks

These characteristics are only provided by systems which have W3G certification. Stainless steel systems burn out after a soot fire and lose their resistance to corrosion. The result: risk of pitting. W3G chimneys with ceramic flue liners are resistant to virtually all types of acid and are long-lasting, quiet and absolutely future-proof.