EVA Stampaggi EVSL8 Manual De Instrucciones página 36

Installation, use and maintenance manual
---- - WOOD BURNING STOVES
4.3 4.3 DRAW DRAW
Fumes heat up during combustion, increasing their volume. Their density is therefore lower than the one of the surrounding
colder air.
This difference between the inside and outside temperatures of the chimney results in a negative pressure which increases
proportionally to the vent pipe length and the temperature.
The draw of the vent pipe must be able to overcome all resistance from the smoke circuit so that any smoke produced inside
the stove during combustion is drawn up and dispersed in the atmosphere through the discharge conduit and the vent pipe
itself.. There are many meteorological factors that influence the operation of the vent pipe, rain, fog, snow, altitude, but most
of all is of course the wind, which can cause thermal depression as well as dynamic depression.
The wind action varies depending on whether it is ascending, descending or horizontal.
● Ascending wind always results in an increased negative pressure and draught.
● Horizontal wind results in an increased negative pressure as long as the chimney cowl was properly installed.
● Descending wind always diminishes the negative pressure, sometimes inverting it.
Excess draught causes an increase in the combustion temperature and consequently a
loss in stove efficiency.
Some of the combustion gases, as well as small particles of combustible material, are
drawn into the flue pipe before being burned, reducing the stove's efficiency and
increasing the consumption of pellets and causing the emission of polluting smoke.
At the same time the high fuel temperature, due to an excess amount of oxygen, wears
down the combustion chamber sooner than expected. On the other hand, poor draught
slows down combustion resulting in a decrease in the stove temperature, fume spillage
inside the room, a loss of stove efficiency and dangerous build-up in the flue pipe.
To avoid excessive draught it is advisable to use a Draught Regulator or Damper (see
figure to the side).
4.4 4.4 STOVE EFFICIENCY STOVE EFFICIENCY
Highly efficient stoves may pose difficulties for fume extraction.
In order for a vent pipe to work properly its internal temperature must increase as a consequence of the fumes generated
during combustion.
Now, the efficiency of a stove is determined by its capacity to transfer most of the head produced into the area to be heated:
the consequence of this is the greater the efficiency of the stove, the cooler the combustion smoke residues are and as a
result the lesser the draught.
A traditional chimney flue, with a rough design and insulation, is more efficient if used with a traditional open fireplace or a
poor quality stove where most of the heat is lost with the fumes.
Therefore, purchasing a quality stove often entails modifying the existing chimney flue to obtain a better insulation, even when
it already works properly with old appliances.
Poor draught results in the stove not operating when hot or in smoke spillage.
Connecting the stove pipe to an existing chimney flue that has
already been used with an old appliance is a common
mistake. In this way two solid-fuel appliances share the same
chimney flue, which is wrong and dangerous.
If the two appliances are used simultaneously, the fume load
might exceed the existing chimney flue capacity resulting in
downdraught. If only one appliance is used, the fume heat will
facilitate draught but the cold air coming from the other
appliance not in use will cool down exhaust fume temperature
again blocking the draught.
Besides the problems described so far, if the two appliances
are placed on different levels the communicating vessel
principle might be interfered with, causing combustion fumes
to be drawn in an irregular and unforeseeable way.
Key: CF - Flue Pipe
ONLY VALID IN GERMANY. In this country it is possible to install stoves in a shared flue.
83103600 - 1.0 - 14/12/2022
EN EN
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