Specifications

If there is insufficient draught in the chimney, it may be a good idea to install the flue pipe
straight up, so as to minimise smoke migration in the actual combustion chamber.
Avoid having any more bends than necessary, and limit the length of the flue pipe so as not to
reduce the draught. Fresh air supply
A wood-burning stove requires air for combustion. As a result, firing a wood-burning stove will help
to create a healthy climate in your house. If the house is very tightly sealed, and particularly if there
is a cooker hood or ventilation system in the house, it may be necessary to install an air grate in
the room in which the woodburning stove is installed. Otherwise there may not be enough draught
in the chimney, which may result in the stove not being able to burn properly, and smoke may
come out of the stove when the fire door is opened.
If it is necessary to install air grates, they must be positioned so that they cannot be obstructed.
1.9 Draught
If smoke comes out of the stove when the fire door is opened, it will be due to the poor draught in the
chimney. This type of stove requires at least 12 pa. of chimney draught to achieve satisfactory
combustion, and to prevent smoke from escaping. Smoke may, however, escape in any event, if the
stove door is opened during very vigorous burning, so this should be avoided. The flue gas temperature
at the rated output is 184°C relative to 20°C.
If in doubt, you may want to get your chimney sweep to measure the draught in the chimney.
Draught
The draught in the chimney is the result of the difference between the high temperature in
the chimney and the cooler temperature outside. Other factors that determine whether
enough negative pressure can be produced to create a draught include the length and
insulation of the chimney, and wind and weather conditions. The draught will be
reduced when:
- The temperature difference is too low, e.g. in connection with a poorly insulated chimney.
If the chimney is cold, it may help to light (burn up) a rolled-up newspaper in the
chimney’s cleaning door.
- The outside temperature is too high, for example during the summer.
- There is no wind.
- The chimney is not tall enough, with the result that it sits in the lee of the roof surface or
tall trees. These conditions are also associated with the greatest risk of smoke coming back
down the chimney.
- Air is entering the chimney in undesired places, e.g. through cracked joints or leaks in the
cleaning door or the flue pipe.
- Unsealed, unused fireplaces are connected to the chimney.
- The flue pipe and chimney are clogged up with soot, due to inadequate cleaning. - The
house is too tightly sealed (please see the section on Fresh air supply).
- Too little air is getting in.
A good draught is achieved when:
- There is a big difference between the temperature in the chimney and outside during
firing, i.e. when the need for heating is greatest.
- The weather is clear and there is a good wind.
- The chimney is of the proper height, i.e. at least 4 metres above the stove, and clear of the
spine of the roof.
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