69
5. The chimney
The stove is tested in accordance with current standards, where a smoke exhauster secures a constant
chimney draft of 10-14 Pascal (Pa). However, with a natural draft (without a smoke exhauster installed) the
chimney draft will increase to 18-25 Pa at optimum conditions. 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 occur problems with smoke coming out
of the door during firing.
Data for chimney calculation
Model
Aduro H1, H2,
H3 Lux & H4 Lux
Aduro H5
Fuel
Wood
Pellets
Wood
Pellets
Flue temperature at [20°C]
273
210
329
170
Chimney draft at testing power [mbar]/[Pa]
0.13/13
0.11/11
0.12/12
0.12/12
Flue gas mass flow [g/s]
5.7
4.7
6.0
3.8
5.1 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 during operation with wood, 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.
The stove will not be able to ignite in pellet operation if there is no draft in the chimney. In this case, the
stove will give an alarm.