5. FLUE
Essential requirements for a correct operation of the device:
• the internal section must be preferably circular;
• be thermally insulated and water-proof and produced with materials suitable to resist to heat, combustion products and
possible condensates;
• not be throttled and show a vertical arrangement with deviations not greater than 45°;
• if already used, it must be clean;
• observe the technical data of the instructions manual;
Should the flues have a square or rectangular section, internal edges must be rounded with a radius not lower than 20 mm. For the
rectangular section, the maximum ratio between the sides must be = 1.5.
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 device: asbestos cement, galvanized steel,
rough and porous internal surfaces. In
gives some examples of execution.
The minimum section must be 4 dm
2
(for example 20 x 20 cm) for devices whose duct diameter is lower than 200 mm or 6.25 dm
2
(for example 25 x 25 cm) for devices 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 device; to avoid
this, tube the flue along its whole height. A too small section causes a decrease of the draught.
ATTENTION
: as far as concern the realisation of the flue connection and flammable materials please follow the requirements provided by
UNI 10683 standard. 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 devices (
).
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 5 at page 41 - Picture 6 at page 42
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
5.2. CONNECTION TO THE FLUE / AIR FOR COMBUSTION (external air intake)
The connection to the stack must be performed with stiff pipes in steel comply with all current Standards and Regulations and to those
envisioned by the Law.
It is FORBIDDEN to use metallic pipes or pipes in asbestos cement since they jeopardize the safety of the fitting itself, considering
that they are subject to tears or breaks resulting in leaks of smoke
.
The exhaust pipe must be air-tight fastened to the stack and can have a maximum inclination of 45°; this to avoid excessive deposits of
condensate produced in the initial start-up phases and/or the excessive gripping of soot and moreover it avoids the slowing down of the
smokes at output.
The failed tightness of the connection can cause the malfunction of the device.
The internal diameter of the connection pipe must be equal to the external diameter of the smokes stub pipe of the device. This is assured
by the pipes complying with DIN 1298.
For a better working of the appliance, it is suggested to have a flue draught of
12 Pa (=1.2 mm of column of water).
The measurement has always to be carried out with hot device (rated thermal performance).
When the depression exceeds 17 Pa (=1.7 mm of column of water), it is necessary to reduce the same by installing an additional draught
regulator (butterfly valve).
IMPORTANT: When using metallic pipes, they must be insulated with proper materials (coatings in insulating fibers resistant up
to 600°C) in order to avoid deterioration of walls or of the counter-hood.
Before positioning the insert in the pre-existing fireplace, it is necessary to close the upper internal part of the stack using (properly pre-
drilled) sheet metal or any other kind of fire-resistant material that can support very high temperatures without suffering any damage. (see
pos.
1 Inserti
).
It is necessary to ventilate continuously the space included between the upper part, the sides of the device and the deflector of the fire-
proofing material of the hood.
For this reason, it is necessary to foresee an intake of air from the bottom (intake of fresh air) and a high output (output of hot air).
Each of these openings must be free and it should not be possible to obstruct it; moreover, they must have a minimum surface of at least
3 dm
2
(example: 30 x 10 cm grating).
In this way, the following targets are achieved
:
• a greater safety
• an increase of the heat created by air circulation around the device.
The heat vent grating
pos.
6
) has to be installed on the upper part of the hood at about 20 cm from the roof. This must
always be installed since its function is that of letting the heat collected within the hood (overpressure) flow out into the room.
18
