ROSSELLA R1 BII – LUNA BII
20
1191015 – EN
A too small section causes a decrease of the draught. It is
suggested a minimum height of 4 m.
The following features are forbidden and therefore they endanger
the good operation of the appliance: asbestos cement,
galvanized steel, rough and porous internal surfaces. Picture 3
gives some examples of execution.
The minimum section must be 4 dm
2
(for example 20 x 20
cm’s) for appliances whose duct diameter is lower than 200
mm, or 6.25 dm
2
(for example 25 x 25 cm’s) for appliances
with diameter greater than 200 mm.
The draught created by the flue must be sufficient, but not
excessive.
A too big flue section can feature a too big volume to be heated
and consequently cause difficulties in the operation of the
appliance; to avoid this, tube the flue along its whole height. A too
small section causes a decrease of the draught.
The flue must be properly spaced from any flammable
materials or fuels through a proper insulation or an air
cavity.
It is forbidden to let plant piping or air feeding channels pass in
the same flue. Moreover, it is forbidden to create movable or fixed
openings on the same for the connection of further other
appliances.
5.1. CHIMNEY CAP
The draught of the flue depends also on the suitability of the chimney cap.
Therefore, if it is handicraft constructed, the output section must be more than twice as big as the internal section of
the flue.
Should it be necessary to exceed the ridge of the roof, the chimney cap must assure the discharge also in case of
windy weather (Picture 4).
The chimney cap must meet the following requirements:
•
have internal section equivalent to that of the stack.
•
have a useful output section twice as big as the flue internal one.
•
be manufactured in such a way as to prevent the penetration of rain, snow, and any other foreign body in the flue.
•
be easily checkable, for any possible maintenance and cleaning operation.
Picture 3
Picture 4
Picture 5
(1) AISI 316 steel flue with double chamber
insulated with material resistant to 400°C.
Efficiency 100% excellent.
(2) Refractory flue with double insulated chamber
and external coating in lightweight concrete.
Efficiency 100% excellent.
(3) Traditional clay flue square section with
cavities. Efficiency 80% excellent.
(4) Avoid flues with rectangular internal section
whose ratio differs from the drawing. Efficiency
40% poor.
A+1/2A
A
Max.
A+1/2A
(3)
(1)
(2)
(4)
50 cm
(1) In case of flues side by side, a chimney cap must be higher
than the other one of at least 50 cm in order to avoid pressure
transfers between the flues themselves.
(1) Industrial chimney cap
with pre-fabricated
elements – it allows an
excellent discharge of the
smokes.
(2) Handicraft chimney cap.
The right output section must
be at least twice as big as the
internal section of the flue
(ideal value: 2.5 times).
(3) Chimney cap for steel
flue with conical deflector
of smokes.
