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6. Draught
If smoke comes out of the insert when the fire door is opened, it will be due to the poor
draught in the chimney. We requires at least 12 PA of chimney draught to achieve
satisfactory combustion and to prevent smoke from escaping.
Smoke may escape in any event if the stove door is opened during vigorous firing, or if the
door is open for more than a few minutes during re-fuelling, so this should be avoided.
The flue gas temperature at the rated output is 135°C to 175°C.
The draught will be reduced when:
- The temperature difference is too low, e.g. in connection with a poorly insulated chimney.
- The outside temperature is too high, e.g. 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.
A good draught is achieved when:
- There is a big difference between the temperature in the chimney and outside,
- The weather is clear and there is a good wind.
- The chimney is of the proper height, i.e. Minimum 4 meters above the stove, and clear of
the spine of the roof
