Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 20
Natural draught flue
Natural draught flues rely on buoyancy from temperature differences to move combustion products upward, with draught increasing with flue height. An essentially vertical flue run is required except for balanced flue appliances discharging directly through an adjacent wall.
Natural draught flue – the combustion products flow into the flue as a result of the buoyancy force produced due to the difference between the temperature of the gases within the flue and the temperature of the ambient air. Draught increases with the height of the flue. Except for those balanced flue appliances which are designed to discharge directly through the wall adjacent to the appliance, a satisfactory natural draught requires an essentially vertical run of flue. See Diagram 1.3(a) and (b).
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