MCZ Antares '03 - Manual (Page 20)

Installation
2.8 Operating problems caused by draught defects in the
flue
Example 1: 8 m/sec wind blowing
downwards at 45°
Example 2: 8 m/sec wind
blowing horizontally
Depression of 30Pa
Wind
High-pressure zone Low-pressure zone
Least favourable points
Most favourable position
Descending wind
Wind
1
2 3
4
Among all the meteorogical and geographical factors
which influence the operation of a flue (rain, fog, snow,
altitude above sea level, amount of sunlight, exposure to
different compass directions), the wind is certainly the one
which has most effect. Besides the thermal depression
brought about by the difference in temperature between
the inside and outside of the flue, there exists another kind
of depression (and overpressure): the dynamic pressure
induced by the wind. A rising wind always has the effect of
increasing the depression and therefore the draught. A
horizontal wind increases the depression if the cowl is
correctly installed. A descending wind always has the
effect of reducing the depression and sometimes of
reversing it.
Besides the direction and force of the wind, the position of the flue and the cowl with respect to
the roof of the building and the surrounding landscape is important. The wind also influences the
operation of the chimney indirectly by creating high-pressure and low-pressure zones, not only
outside the building but inside as well. In rooms directly exposed to the wind (2), an indoor high-
pressure area can be created which can augment the draught in stoves and fireplaces, but it can
be counteracted by the external high pressure if the cowl is situated on the side exposed to the
wind (1). On the other hand, in the rooms on the opposite side from the direction of the wind (3), a
dynamic depression can be created which competes with the natural thermal depression
developed by the chimney, but this can be compensated for (sometimes) by locating the flue on
the opposite side from the direction of the wind (4)
1-2 High-pressure zones
3-4 Low-pressure zones
The operation of the pellet stove is noticeably
sensitive to the conformation and position of
the flue which is adopted.
Hazardous conditions can only be overcome
by suitable setting-up of the stove carried out
by qualified MCZ personnel.
Trees/hills/other buildings
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