Baxi CBP Matic 18 Manual De Instrucciones página 176

Failure to comply with the requirements here detailed may prevent the correct
operation of the unit. Follow all the instructions presented on the diagrams.
The boilers operate with the combustion chamber in depression, which is why it
is absolutely necessary that they include a fume exhaust pipe to adequately extract
combustion gases.
Fume duct material: The tubing must consist of 0.5 mm thick rigid stainless steel,
with fastening joints attaching the different sections and accessories.
Insulation: The fume ducts must be double-walled and insulated to make sure that
fumes do not cool down going outwards, which would cause an inadequate
circulation and condensation that may damage the unit.
Output "T-tube" : Always attach a regulator "T-tube" to the output of the boiler.
Windproof terminal: A windproof terminal must always be installed to avoid the
backflow of fumes.
Chimney draught: The figures below show three standard diagrams, specifying
adequate lengths and diameters. Any other type of installation must guarantee a
draught of 12 Pa (0.12mbars) measured when hot and at the maximum power.
Ventilation: To ensure the boiler's optimum operation, the installation location
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should be fitted with an air vent, with a minimum cross-section of 100 cm ,
preferably close to the unit's back panel. The boiler includes a circular pipe (
50mm) that may be routed to the exterior of the house.
4.4. Installation with a shaft
As shown in Figure 7, the pellet-run boiler is installed with a  100 mm exhaust pipe
directed up the chimney. If the chimney is too large, an 80 mm-wide pipe should be
installed at the fume outlet.
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