HDG Lambda-Control 1 plus - Water Content - Moisture of the Fuel; Refuel Amount; Energy Content and Usable Energy Content of the Fuel

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1.19 Water content – moisture of the fuel
Generally a wood boiler can burn wood in its natural form, if its water content (w) is lower than 20%. A high moisture
content in fuel can lead to complications while burning and reduces the efficiency of heating and the dispensed amount
of energy. Therefore, please read the manufacturer’s specification. They provide information about what combustibles
with what water content are permitted. Depending on the storage location and time, fuel can contain various amounts
of moisture:
Storage Time
Water content w (%)
Humidity (Atro) u (%)
(stored covered outdoors)
Water content w (%)
Humidity (Atro) u (%)
(stored indoors)
“Moisture” settings in
controller
Months
w (%)
u (%)
w (%)
u (%)
u > 28%: “high”
u = 17 – 28%: “medium”
u < 17%: “low”
3
44
78
36
56
9
26
35
23
30
18
17
20
15
17
24
16
19
14
16
30
15
17
13
15
The following basic rules should also be observed:
Firewood must be stored for at least 18 months indoors or 24 months covered outside.
For the boiler:
● Short logs should be arranged in an offset pattern to use the full capacity of the fuel
chamber.
● Make sure there are small gaps in the fuel stack for air. Squared timber and waste wood
need to be chopped to avoid compact compounds.
● The wood must be stacked in a way that the fuel can slide and does not create a large free
space.
1.20 Refuel amount
Please note the density and energy content amounts described in chapter 1.18. Also, make sure that the heating system
is not hot when beginning the setback operation. Refuelling before the setback operation is only permitted, if it does
not result in overtemperature.
BSB automatically calculates the appropriate amount of fuel and energy.
1.21 Energy content and usable energy content of the fuel
The energy contents, also called heating value (Hu), do not always correspond with the specifications; i.e. wood pellets or
wood briquets with 5.8 kWh/kg would only be possible, if NOT ONLY natural wood was used to produce them. The energy
content of spruce is, depending on the location, between 5.0 to 5.2 kWh/kg with a water content of w=0% (dry substance).
The averaged energy content is 5.15 kWh/kg at w=0%. However, in practice a water content of less than 10% is hardly
found.
If w=10%, 1000 kg wood (of any type or form) consist of 900kg dry substance and 100 litres of water. Per litre of water,
a loss of 0.68kWh must be deducted (vapour energy).
Usable energy content of spruce/kg with a water content of 15%:
If w=15%, it is 4.25 kWh/kg. Applying a boiler efficiency grade of 91%, 4.25 x 0.91 = 3.86 kWh/kg is available as usable
energy.
Usable energy content of spruce/m3 (cubic meter) with a water content of 15%:
At w=15% it is 1520 kWh/m3 Applying a boiler efficiency grade of 91%, the usable amount of energy is 1520 x 0.91 =
1383.2 kWh are available.
The usable energy is generally reduced by the system efficiency grade (also called annual efficiency grade), mainly through
energy needed to heat the actual boiler and the water therein to 85°C – which cannot be used after firing entirely for
heating purposes. This is especially the case with low heating demands and when the accumulator is loaded to capacity
after burning.
Therefore the setting in “Accumulator” → “Settings” → 9.02 Acc. reserve should only be set to 0%,
if the sensor positioning is Logotherm conform – and only if no backup for heating or solar is
needed.