Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 59·4.12
Size of natural draught flues for open-flued appliances
Natural draught flues must be sized according to Table 4.2 to match the intended appliance, ensuring adequate discharge velocity while avoiding excessive flow resistance.
A flue should be sized in accordance with Table 4.2 to suit the intended appliance and to ensure an adequate discharge velocity to prevent flow reversal problems but not to impose excessive flow resistance.
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