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5.3. EXPANSION
TANK
According to the regulations in force in Italy, any heating appliance with solid fuels must be equipped with
open expansion tanks.
5.4. FLUE
DUCT
The flue duct is very important for the proper operation of the boiler; it must be seal and thermal insulated.
Old or new flue ducts, built without respecting the above prescriptions, can be reused introducing a metal
duct in the interior. Another metal duct must be introduced in the interior of the existing flue duct filling the
gap between the external surface of the inner duct and the internal surfaces of the old duct with insulating
materials. Flue ducts realized with cement blocks must have any joint perfectly sealed to avoid the
condensate sticking to the inner surfaces staining the external wall.
The construction of new flue ducts requires setting up a project satisfying any prescription required by the
regulations in force.
In any case the flue duct must feature a good draft, at least 2 mm of water column depression at the base of
the duct when cold. Lower draft values will cause the boiler cutting off completely during the stand by periods
and tar and condensate will stick in the air inlet passages. On the other hand, too high draft values will cause
high thermal inertia and poor fuel economy.
We recommend anyway the use of a draft adjusting device to keep a constant depression value in the duct,
to avoid unwanted power raising.
