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3
FUELS
The HERZ firestar boiler should be operated with
the fuels and their properties which are described
in this chapter.
3.1
Log wood
The HERZ – firestar is suitable for burning logs to
operate central heating systems for closed hot
water installations. Smaller split logs enable
higher boiler performance than whole ones. We
recommend triangular firewood with side lengths
of 50 cm and edge lengths of 8 cm. Too coarse or
too
long
firewood
performance and hollow fire. The heat value of the
wood is primarily dependent on its moisture
content. The heat value decreases with increased
moisture. The combustion of wood with high
moisture content also causes a decrease in the
degree of efficiency of the boiler.
Wood should therefore be stored for at least two
years in a dry, ventilated place. Oak needs to be
stored for about a year longer. Dry bark displays a
heat value similar to wood but there is more likely
to be increased formation of ash.
The burning of unsuitable fuels could lead to
uncontrolled combustion. The guarantee becomes
invalid! Operational faults and consequential
damage are likely to occur.
Possible consequential damage:
◼
Damage to the thermodynamic combustion
chamber, the lambda probe, the flue gas
probe due to aggressive residues in the
boiler
◼
Sooting or corrosion in the filling area due to
condensation as a result of using fuel that is
too moist.
◼
The escape of flue gas from the airflow
apertures through uncontrolled combustion
(deflagrations).
◼
Combustion time at nominal load up to
Combustion time in hours
Type
FS 18
Softwood
5
Hardwood
6
Wood
3
chips
may
lead
to
reduced
FS 20
FS 30
FS 40
6,5
6
3,5
8
7
4,5
4
3,5
2,5
3.2
Suitable fuels
The firewood must be air dried, that is, dried at
least one year with water content below 20 %
preferable half-meter logs with an average
diameter of 10 cm. If the cleavage planes of the
log wood are much larger, the log wood should be
thinner, in extreme cases 20 to 5 cm.
Small sized material may be burned only as
admixture. From the smaller material may be
added less. Wood briquette with 6 to 10 cm
diameter according EN 17225-3.
Only one oversized log each boiler filling
To split a root stock to such thin pieces is very
hard work. Per boiler filling maximum one large
root stock piece are burned up in the stack.
Type of
Calorific values (by wood
wood
moisture 25%) in kWh/stere
Beech
Oak
Pine
Spruce
We recommend to use beech
wood. Do not mix different types
of wood. The use of one type of
wood
burn-off and reduces burning
disturbance. However, if it cannot
be avoided to use different types
of wood, the boiler must be filled
in
layers
hardwood above).
3.3
Not suitable fuels
When burning wet fuel with more than 30% water
content,
condensation
corrosion on the walls of the filling chamber occur.
Fuels
3
1890
1930
1520
1330
promotes
a
consistent
(softwood
below,
water
formation
and
7
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