4 | Operating the System
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B1510622_en | Operating instructions Firewood boiler S4 Turbo
Fuel table
The table below shows a selection of wood types with the corresponding energy content
depending on the water content:
Wood type
Energy content with water content [kWh/kg]
w = 15%
w = 20%
w = 25%
Spruce
4.3
4.0
3.7
Pine
4.3
4.0
3.7
Beech
4.1
3.8
3.5
Oak
4.1
3.8
3.5
If fuels with a water content below 15% are used, adjust the air duct accordingly,
Fill level in boiler
The table below shows the relationship between fill level and weight. It compares beech
(example of hardwood) and spruce (example of soft wood) with a water content of
approx. 20%. Using our example above with beech, the fill level of an S4 Turbo 34 would,
therefore, be approx. one third.
Fill level
Weight at fill level
S4 Turbo 15-28
S4 Turbo 32-60
3/3
Beech
approx. 45 kg
approx. 55 kg
Spruce
approx. 28 kg
approx. 33 kg
2/3
Beech
approx. 30 kg
approx. 37 kg
Spruce
approx. 19 kg
approx. 22 kg
1/3
Beech
approx. 15 kg
approx. 18 kg
Spruce
approx. 9 kg
approx. 11 kg
4.3.7 Reloading intervals when operating without storage tank or if the storage tank is
too small
NOTICE
Feed based on output:
Only replenish the fuel if energy is needed!
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If too much fuel is loaded, the boiler drops below its minimum output limit and goes
over to "constant burn" operating status (blower fan switches off)
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The level of efficiency drops in constant burn mode, the emissions increase and
the boiler can tar up (pitch formation!)