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Instructions for the installer
4.2 - FIRE WOOD
Wood is formed mainly by cellulose and lignite. It
contains other substances, such as resin
(fir - pine), tannin (oak - chestnut) and, obviously, a
large quantity of water.
Good quality woods are oak, ash, beech, maple
and fruit trees, except cherry; medium quality wood
is: chestnut and birch; sufficient quality wood: lime
tree, poplar and willow. Resinous trees are, normally, medium
quality fuels.
Wood is therefore an extremely heterogeneous fuel, due to dif-
ferent essences (beech, oak, fruit, resinous), different moisture
content, and due to different shapes and dimensions.
Boiler operation will, of course, be certainly effected by all these
factors. Especially by the log dimensions, the moisture content
and the way wood is loaded in the boiler.
4.3 - WOOD MOISTURE
The calorific value of the different types of wood
depends on their moisture content, as shown on
the table. Boiler output and autonomy will diminish
as the moisture increases. In the table a reduction
factor is indicated according to the moisture content
of the wood used. The heat output of the AIREX 2S
boiler is calculated for wood with a 15% moisture
content.
As an example wood which has been dried for 2
years air in a protected area has a 25% moisture
content.
Example:
Moisture content of wood used = 30%
Heat output = nominal heat output x 0,79
Correction factors for wood moisture content
%
moisture
Calorific
value
kcal/kg
Correction
factor
15
20
25
30
35
40
45
50
3.490
3.250
3.010
2.780
2.540
2.300
2.060
1.820
1
0,93
0,86
0,79
0,72
0,65
0,59
0,52
4.4 - FIRE WOOD DIMENSIONS
The dimensions, together with the moisture content,
contribute to determine the boiler’s output Small
pieces (with a length, however, conforming to indi-
cations hereby indicated) are more easily
inflammable and therefore have the tendency to in-
crease the boiler’s output and therefore to reduce its
autonomy. Moreover, they fall with greater facility, in
the lower chamber, reducing the risk of the formation of “bridges”.
The so-called “bridge” is an empty space in the fire wood storage
room, where unburnt wood logs remain . In this case the bed of
embers is not fed with continuity and the refractory burner’s slot
is uncovered. In these conditions, preferential air passages are
created with a very small flame due to an excess of air.
4.5 – INITIAL LIGHTING CHECKS
GENERAL CONTROLS
During the first ignition check that the C.H. system
has been properly filled and properly purged, that
the safety heat exchanger is connected to the water
mains via the thermal safety discharge valve (fig.
10, page 15 and fig. 17 page 18), that the chimney
has a sufficient draught, that the electrical con-
nection has been made correctly (paragraph 3.12
& 3.13) and that the recirculation and boiler pumps
are not blocked.
Furthermore check that the stainless steel grate
and the fire bars are properly positioned.
THE BY-PASS
The by-pass is a direct passage between the fire
wood storage room and the chimney. It is normally
closed by a mobile shutter. The by-pass is automa-
tically opened or closed via a pushing rod when the
loading door is opened.
In this way the smoke accumulated in the fire wood storage room
is aspirated and sent to the chimney directly.
The bypass, in conclusion, allows the smoke to be discharged
at the chimney without escaping from the loading door when
loading the wood or during lighting.
Any way, it is essential to open the loading door slowly and, as
well, to rotate the antismoke flap (pos. 4, fig. 2) gradually so that
the smoke is effectively aspirated.
BY-PASS CONTROL
During the installation stage and, in any case, before starting to
use the boiler, check that the by-pass is correctly closed and the
actuator of the microswitch, which controls the opening of the
door, is correctly positioned.
In this way when the door is closed
the fan has to start rotating; when the door starts to open the fan
has to be OFF, otherwise all the smokes comes out.
