What is a Commercial Boiler Flue?
A commercial boiler system heats water for warming buildings. Any boiler exceeding 70kW output qualifies as commercial. The flue removes combustion products from the building into the atmosphere — essentially a pipe that is attached to the boiler and goes outside of the building. The terms flue and chimney are used interchangeably, with the chimney being the shaft housing the flue itself.
Types of Chimneys and Flues
Twin Wall System Chimney
Two concentric stainless steel walls with insulation between them, designed for condensing/non-condensing appliances, fuel generators, and high-pressure applications.
Single Wall Chimneys
Designed for multi-fuel applications as chimney liners or connecting flues for condensing and non-condensing systems.
Flexible Liner
Stainless steel liners reline existing chimneys. Single-skin versions suit gas appliances; twin-skin versions work with wood, multi-fuel, gas, or oil appliances.
Commercial Boiler Flue Regulations
Key regulatory requirements include CE marking, temperature ratings (400°C for multi-fuel, 200°C for gas/oil), condensate resistance, corrosion resistance, liner material specifications, and soot fire resistance.
Installation considerations: chimneys should be as vertical as possible, with a 600mm vertical rise recommended before direction changes. Proper support, inspection points, and test points along the flue length are necessary for compliance.
Conclusion
Selecting the appropriate flue prevents performance issues and safety hazards related to combustibles proximity and emissions standards.