3 Mode of operation – Fuel quality requirements
20
results in a steadily decreasing output of the (central-heating) boiler,
greater amounts of ash and smoke, as well as making it increasingly
unfit for storage. In addition, this can lead to extensive tarring of the
boiler, the flue pipe and chimney, and cause a chimney fire.
Logs should therefore be split before they are cured. This is done in
order to achieve a water content which makes them suitable for
burning within a reasonable amount of time (approx. two years).
The maximum permissible water content of log wood for the HDG
Euro 30/40/45/50 is 20% (M20).
For technical considerations, a representative calorific value is
selected depending on water content. For burning that is both
economical and low on emissions, the calorific value should not be
less than 4 kWh/kg.
W
OOD
CHIPS
Essential criteria for the definition of the property classes are particle
size, moisture content and ash content of the fuel.
P
ARTICLE
SIZE
In accordance with DIN EN ISO 17225-4, the fuel specifications for
wood chips are classified in P45S. The numeric value of the P class
refers to the size of the wood chips in mm, which fit through a
circular mesh with the indicated sieve opening size.
•
P45S
For HDG Euro 30/40/45/50, wood chips classified in the P45S
category or larger can be used as fuel.
W
ATER
CONTENT
The water content in accordance with DIN EN ISO 17225-4 for
property class A1 with M10 (≤ 10 %) or M25 (≤ 25 %) differs here from
the water content for property class A2 with M35 (≤ 35 %). The
maximum permissible water content for wood chips is 20 % (M20)
and therefore corresponds to the property class A1.
Water content
Moisture
Calorific value
Relative wood
consumption
10.0 %
11.1 %
4.6 kWh/kg
87 %
20.0 %
25.0 %
4.0 kWh/kg
100 %
26.0 %
35.0 %
3.7 kWh/kg
110 %
30.0 %
42.9 %
3.4 kWh/kg
120 %
Table 3/2 - Calorific value depending on water content
P class
Main content
(mass fraction min.
60%)
Fine content
(% by weight)
≤ 3.15 mm
Coarse content
(% by weight)
Max. length, max. cross section
P45S
3.15 mm < P ≤ 45 mm
≤ 10 %
≤ 10 % > 63 mm, all ≤ 200 mm, cross
section of the outsized particles ≤ 6 cm
2
Table 3/3 - Particle size
