Baxi PRIME HT 240 Installers And Users Instructions page 14

Figure 11
A 90° bend reduces the total duct length by 0.5 metre.
A 45° bend reduces the total duct length by 0.25 metre.
SEPARATED HORIZONTAL FLUE TERMINALS INSTALLATION OPTIONS
IMPORTANT: Ensure a minimum downward slope of 1 cm toward the boiler per each metre of duct length.
Make sure that the exhaust and intake ducts are securely fixed to the walls.
L max = 15 m
14
INSTRUCTIONS FOR THE INSTALLER
(L1 + L2) max = 80 m
The maximum length of the suction
duct must be 15 metres.