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7. Fuel Load Sizes and Thermal Output
The thermal output depends on the amount of fuel you burn in the stove (fuel load size).
When adding more fuel (e.g. wood), the maximum fuel load size is 2 kg. Exceeding the
maximum fuel load size leads to a danger of overheating, possibly resulting in damage to
the stove and risk of a stove fire.
A thermal output of 7 kW can be attained by burning wood logs weighing approx.
1.6 kg and approx. 20 - 25 cm in length for approx. 45 min.
To attain thermal output of 3.5 kW, burn wood logs weighing approx. 0.8 kg and
approx. 20 cm in length for approx. 45 min.
The Lisboa is intended for intermittent operation, please only apply one fuel layer at a
time.
8. Regulating the Combustion Air
When lighting the fire and adding fuel, the combustion air is regulated with the primary air
and secondary slider.
8.1 Primary Air
The primary air is guided through the grate and into the fire box from below, thus more
quickly achieving the required fire box temperature during the warming up phase.
8.2 Secondary Air
The secondary air is guided into the fire box via air ducts from the top. It supplies the fire
box with the volume of preheated oxygen necessary to completely burn off the wood gas
and ensures that the fire box window remains free of soot.
For regulating the secondary air, the following general rule applies: a small fire
requires little secondary air; a large fire requires ample secondary air.
If the secondary air valve is closed too tightly, there is the risk of the flue gases not com-
pletely burning (smouldering fire) and/or soot build-up on the fire box window or that the
amassed wood gases will burn explosively (over firing/deflagration).
Please note: Burning wood when the primary air slider is opened too wide poses the risk of
overheating the stove (forge fire effect). During operation, the secondary air slider should
never be completely closed. The fire box door and ash compartment must always be tightly
shut.
Fig. 4
The control elements.
1
3 2
1
3
2
Secondary air slider (II)
Primary air slider (I)
Shaking grate operating device