Draft Conditions - Heta SCAN-LINE 40 Operating Instructions Manual

a damper is fitted in the flue gas pipe,
there must always be at least 20 cm
free passage, even when the damper is
in its "closed" position. If local regula-
tions permit, two contained fireplaces
can be connected to the same chim-
ney. However, you must abide by local
regulations regarding the distance
between the two connections.
Wood-burning stoves must never be
connected to chimneys that are also
linked to a gasfired heater. An ef-
ficient stove makes high demand on
chimney properties – so always have
your local chimney sweep evaluate
your chimney.
Connection to a brick chimney
Brick a thimble into the chimney and
seat the flue gas pipe in this. The
thimble and flue gas pipe must not
penetrate the chimney opening itself,
but must be flush with the inside
of the chimney duct. Joins between
brickwork, the thimble and flue gas
pipe must be sealed with fireproof
material and/or beading.
Connection to a steel chimney
When fitting a connection from a
top-output stove directly to a steel
chimney, we recommend fitting the
chimney tube inside the flue gas spi-
got so that any soot and condensation
drops into the stove itself rather than
collecting on the exterior surface of
the stove. For connections to chimneys
that are run through ceilings, all natio-
nal and local regulations regarding
distance to flammable material must
be followed. It is important that the
chimney is fitted with roof support so
that the top panel of the stove is not
required to bear the entire weight of
the chimney (excessive weight may
damage the stove).

Draft conditions

Poor draft may result in smoke being
emitted from the stove when the door
is opened. The minimum chimney
draft to ensure satisfactory combu-
stion in stoves of this kind is 12 PA.
However, there will still be a risk of
of
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smoke emission if the firing door is
opened during powerful firing. The
flue gas temperature at nominal
output is 257°C when expelled to an
exterior temperature of 20°C. The flue
gas mass flow is 6 g/sec. The chimney
draft is generated by the difference
between the high temperature of the
chimney and the low temperature of
the fresh air. The length and insulation
of the chimney, wind and weather
conditions also have an effect on the
ability of the chimney to generate ap-
propriate under-pressure.
If the stove has not been used in a
while, check that the chimney and
stove are not blocked with soot, bird
nests, etc., before using it.
Reduced draft can occur when:
• The difference in temperature
is too small - due to insufficient
chimney insulation, for example.
• The outdoor temperature is too
high in summer, for example.
• No wind is blowing.
• The chimney is too low and shel-
tered.
• The chimney contains false air.
• The chimney and flue gas pipe are
blocked.
• The house is too airtight (i.e. when
there is an insufficient supply of
fresh air).
• Poor smoke extraction (poor draft
conditions) due to a cold chimney
or bad weather conditions can be
compensated for by increasing the
airflow into the stove.
Good draft occurs when:
• The difference in temperature
between the chimney and outdoor
air is high.
• The weather is fine.
• The wind is blowing strongly.
• The chimney is of the correct
height: at least 4.00 m above the
stove and free of the roof ridge.
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