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Flue Draught
The chimney can be checked before the appliance is installed with a smoke
match. If the flue doesn’t pull the smoke, it may suggest the flue needs
attention.
This test is only a guide as an apparently poor flue may improve once the
appliance is installed, lit and the flue is warmed. Once the appliance is installed
a flue draught reading should be taken as detailed below.
Two flue draught readings should be taken, one with the appliance at minimum
burning rate and one at maximum burning rate. The flue draught test hole must
be drilled in the flue pipe as close to the appliance as possible and before any
flue draught stabiliser.
Minimum reading: The appliance should be lit and allowed to warm the flue
thoroughly. Close the air controls, and ensure firebox door is fully closed. Allow
the burning rate to become steady. The flue draught reading should now be
taken; the minimum required is 12 Pascals [Pa] (0.05’’ w.g.).
Maximum reading: The air controls can now be opened to allow the appliance
to burn at maximum rate. Take a flue draught reading.
Ideally, the flue draught readings should range between 12Pa, 0.12mm (0.05’’
w.g.) and 25Pa, 2.5mm (0.1’’ w.g.). Any readings significantly outside this range
may indicate the need for remedial action. Low flue draught symptoms: difficult
to light and smoke coming into the room. High flue draught symptoms: fuel
burns away very quickly, overfiring which may damage the appliance &
invalidate the warranty.
A flue stabiliser can be fitted to reduce the draught through the appliance if the
draught may exceed 25Pa. The flue stabiliser should be fitted in the same room
as the appliance and be the same size as the flue pipe. Consult building
regulations regarding additional ventilation.
A fan flue booster can also be fitted if the flue draught is poor. This should be
fitted according to the instructions supplied with the booster. An electrical
supply will be needed.
