Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 33·2.41
Limits on flue bends and changes of direction
Flue systems must limit the number and configuration of bends to enable sweeping and inspection, with a maximum of four 45° bends total and not more than two between access points, treating 90° factory-made bends as equivalent to two 45° bends.
Provisions should be made to enable the flue to be swept and inspected. The number of changes of direction between the combustion appliance outlet and the flue outlet should be limited to not more than four 45º bends with not more than two of these being between an intended point of access for sweeping and either another point of access for sweeping or the flue outlet. 90º factory-made bends, elbows or tee pieces in flue pipes should be treated as being equal to two 45º bends.
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