User Manual

4. The chimney

The optimum combustion is achieved at a constant chimney draft of 10-14 Pascal (Pa) measured in the flue

pipe above the stove (when having a smoke exhauster). However, with natural draft (chimney without smoke

exhauster) the draft in the chimney will be between 18-25 Pa when conditions are optimum. There are many

factors that affect the chimney draft, including the outside temperature, wind strength, and surrounding

buildings. There are no requirements with respect to specific chimney heights, but a chimney must be tall

enough to provide a good draft. If the recommended chimney draft is not achieved, there may be problems

with smoke out of the door by firing.

Data for chimney calculation

Wood

Flue temperature at [20°C]

273

Chimney draft at testing power [mbar]/[Pa]

0.13/13

Flue gas mass flow [g/s]

5.7

4.1 Inadequate draft in the chimney

If you experience poor draft in the stove after the installation, please make sure that there is nothing in the

chimney to restrict the smoke and that no nearby buildings or trees affect the winds around the chimney.

If the chimney is too short, leaks, or is inadequately insulated, there may be problems with the chimney draft

(let the chimney sweep assess this). The draft should be sufficient during the ignition phase when the

stove/chimney is cold to provide a clean combustion and prevent smoke leakage. Therefore, we recommend

a chimney draft around 5 Pa in the ignition phase.

Once the ignition is a success and the smoke temperature is rising, it is important that the chimney draft

reaches a stable area around 18-25 Pa in operation (1 hour after ignition) when the chimney/stove is hot.

The draft in the area of 18-25 Pa when the stove is hot is essential in order to achieve an optimum and clean

combustion and avoid problems such as pellet accumulation and smoke leakage. Therefore, we recommend

that you measure your chimney draft when the chimney is cold and when it is hot after 1 hour in operation.

In practice, the chimney draft will differ – especially in cold condition. Therefore, the best indication of the

chimney draft is to measure the draft when it is hot. If the chimney sweep judges the draft to be sufficient, but

you still have problems lighting a fire in “wood mode”, try extending the fire lighting phase by using more thin

pieces of kindling and 1-2 firelighters, so that the chimney gets thoroughly warm. The chimney will not draw

at optimum effect until it is warm. When a layer of embers has been formed, add 2-3 dry logs.

When in "pellet mode", the stove will not be able to ignite and instead give the alarm “failed ignition” if there

is not enough chimney draft in the ignition phase. If you experience that the stove does not turn on in the first

or second attempt but instead shows the alarm “ignition failed”, it is important that you do not try to turn on

the stove again. Instead, wait until there is no more smoke in the combustion chamber, and then move the

brazier to the side and scrape the pellets away if they have accumulated. You can now put the brazier back

in place. Remember to check if it is placed correctly. Then, you can turn on the stove again. The alarm

“ignition failed” is often caused by an insufficient chimney draft. You can create chimney draft by igniting

some paper or small pieces of firewood - this can sometimes remove pockets of air in the chimney.

If it is impossible to establish a sufficiently natural chimney draft, the chimney can be fitted with a smoke

exhauster, e.g. Aduro DraftOptimizer.