Morso 1010 - Draft Conditions; Understanding Chimney Draft

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1.9 Draft conditions
If smoke spillage occurs when the re door is opened, it is probably due to poor chimney
draft. This type of stove requires at least 12 pa of chimney draft to achieve satisfactory com-
bustion and smoke spillage prevention. However, in cases where the stove door is opened
too vigorously you could expect that slight smoke spillage may occur.
The smoke gas temperature at the rated output is 152˚ C relative to 20˚ C.
If you have any doubts, you may want to have your installer measure the draft in the chimney.
Draught
e draught in the chimney is the result of the dierence between the high temperature in the chimney
and the cooler temperature outside. Other factors that determine whether sucient 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:
- e temperature dierence 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.
- e outside temperature is too high, e.g. during the summer.
- ere is no wind.
- e chimney is not tall enough, with the result that it sits in the lee of the roof surface or tall
trees.
ese 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 ue pipe.
- Unsealed, unused replaces are connected to the chimney.
- e ue pipe and chimney are clogged up with soot due to inadequate cleaning.
- e house is too tightly sealed (please see the section on Fresh air supply).
A good draught is achieved when:
- ere is a big dierence between the temperature in the chimney and outside, i.e. when the
need for heating is greatest.
- e weather is clear and there is a good wind.
- e chimney is of the proper height, i.e. Minimum 4 metres above the stove, and clear of the
spine of the roof.