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FLUE DRAUGHT
The chimney can be checked, before the stove is installed, with a smoke match. If the
chimney doesn't pull the smoke it may suggest the chimney needs attention (see the Flue
Diagnosis Table, below).
MEASUREMENTS
The flue draught test hole must be drilled in the flue pipe as close to the stove as possible
and before any flue draught stabiliser.
MINIMUM
The stove should be lit and allowed to warm the flue thoroughly. The air controls can then
be set so that the stove burns on a low setting. Allow the burning rate to become steady.
The flue draught reading should now be taken with the primary air intake closed and the
airwash control fully open.
MAXIMUM
The primary air intake can now be opened to allow the stove to burn at maximum rate. Give
the stove some time for the burning rate to become steady and then close the primary air
intake, make sure the airwash control is fully open and take a flue draught reading immediately.
Ideally, the flue draught reading should range between 1mm wg (10 Pa) and 2.5mm wg (25 Pa).
Any readings significantly outside this range may indicate the need for remedial action.
CAUSE
REMEDY
Cold chimney
Line the chimney
Chimney too short
Extend the chimney
Down draught
Relocate/extend chimney terminal. Fit an anti down draught cowl
Chimney diameter too large
Line the chimney
Chimney obstruction
Clear/sweep the chimney
Restricted air supply
Check for competing draughts (other chimneys, extractor hoods/fans).
Fit an air vent if the room is sealed
CAUSE
REMEDY
External wind conditions combined
with chimney terminal
Fit stabiliser cowl.
Fit flue draught stabiliser.
Low flue draught symptoms:
Low flue draught symptoms:
Low flue draught symptoms:
Low flue draught symptoms:
difficult to light and smoke coming into the room.
High flue draught symptoms:
High flue draught symptoms:
High flue draught symptoms:
High flue draught symptoms:
fire difficult to control, fuel will not last, stove too hot, stove damage, chimney fire.
This test is only a guide as an apparently poor flue may improve once the
stove is installed, lit and the flue is warmed. If, once the stove is installed,
there is any doubt that the chimney is providing an adequate draught, a flue
draught reading can be taken with the stove lit. Two flue draught readings
should be taken, one with the stove at minimum rate and one at maximum
rate.
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Fig. 2 - Chimney and Flue Performance
Fig. 2 - Ideal Flue Connections
Effect of adjacent buildings, hills
or tall trees on the exit of flue gases
Available from
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