7
2.5 CONNECTING UP “MURELLE” FLUE
The flue for expulsion into the atmosphere of the products
of combustion from natural draught appliances must
meet the following requirements:
– be gas-tight to the products of combustion, waterproof
and thermally insulated;
– be built of materials suitable for resisting over time nor-
mal mechanical stresses, heat, and the action of pro-
ducts of combustion and their possible condensates;
– follow a vertical path and not present any throttling
throughout its entire length;
– be adequately insulated to prevent phenomena of
condensation or cooling of fumes, in particular if loca-
ted outside the building or in unheated ambiences;
– be set at an adequate distance from combustible or
easily inflammable material by means of an air gap or
suitable insulating material;
– have beneath the mouth of the first smoke duct a
chamber for collecting solid material and any conden-
sate; the height of the chamber must be at least 50
mm. Access to the chamber must be guaranteed by
means of an opening provided with an air-tight metal
door;
– have a circular, square, or rectangular internal cross
section; in the case of square or rectangular sections,
the corners must be rounded off with a radius of not
less than 20 mm. However, hydraulically equivalent
cross sections are allowed;
– be equipped with a chimney-pot at the top, which
must be outside the so-called back-flow zone, so as to
prevent the formation of back-flow, which prevents
free discharge of the products of combustion into the
atmosphere;
– be devoid of mechanical means of suction located at
the top of the pipe;
– no overpressure should be present in a chimney that
passes within or close up to inhabited rooms.
Fig. 6 refers to the connection of the boiler to the flue or
chimney through smoke ducts. When making the con-
nection, in addition to respecting the dimensions given,
you are recommended to use gas-tight materials capable
of resisting over time mechanical stresses and the heat of
smokes. At any point along the smoke duct, the tempe-
rature of the products of combustion must be higher than
dew point.
More than a total of three changes of direction must not
be made, including the inlet connection to the
chimney/flue. For any changes of direction use only cur-
ved lengths of pipe.
Fig. 7 shows some applications of draught terminals that
ensure proper expulsion of products of combustion in
case of discharge through the wall.
SLOPE
min. 3%
2.500 mm max.
SLOPE
min. 3%
SLOPE
min. 3%
Fig. 6
Fig. 7
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