If smoke comes out of the stove when the fire door is opened or through the air inlets when the door is closed, it will probably be due to the poor draught in the chimney.
If in doubt, you may want to get your chimney sweep to measure the draught in the chimney.
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 sufficient 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.
- 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.
- 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. An air vent may need to be installed in the room to comply with building regulations (for solid fuel stoves with an output over 5kw).
A good draught is achieved when:
- There is a big difference between the temperature in the chimney and outside, 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. Minimum 4 metres above the stove, and clear of the spine of the roof.