15
INSTALLATION AND OPERATION MANUAL
the chimney and protects the masonry from destruction due to the impact of condensate. Internal diameter of the liner should
be no less than the external diameter of the smoke exhaust pipe of the boiler. The chimney liner can be round or oval. It is not
recommended to use rectangular-shaped liner as, due to the temperature fluctuations, its walls deform, gaps appear at the
element junction points, through which the condensate falls on the walls of the bricks chimney. Additional air is sucked in, which
reduces draught of the chimney. Draught for each boiler model should correspond to the referred value of draught in the table
“Technical data”. The liner should be factory made. Minimum permissible height of the chimney should be at least 6m. The top
of the chimney should be above the ridge at least by 0.5m. If the chimney is further from the ridge than 1m, the angle horizon-
the ridge- the cap of the chimney should consist 10° or less degrees. Draught of the chimney can also be negatively affected by
various obstructions near the building: trees, hills, other buildings. Fig. 9 presents the recommended minimal angles between the
chimney, nearby objects and the horizon. Angles larger than those indicated will cause reduction of draught of the chimney.
The connection of other devices to the chimney to which the boiler is connected is prohibited.
The chimney should be cleaned at least once a year!
6. fUel
The boiler is fired only by wood logs and wood briquettes. It is possible to fire it with fuel peat briquettes, however the operation
of the boiler becomes less comfortable for the user as it is necessary to remove the ashes of these highly ash-producing briquettes
after each loading. The ceramic elements of the lower chamber can be damaged if they are removed every day when cleaning,
thus their lifetime will be shorter. Therefore, we recommend usage of fuel peat briquettes only in rare, exceptional cases.
It is recommended to fire dry firewood with a moisture content of 12-20 %. The drier the firewood, the larger its calorific capacity.
When the moisture content of the firewood is 20%, the heat potential of 1 kg is approximately 4 kWh; when the moisture
content is 50%, its heat potential is reduced by half.
The length of the firewood should be at least 5cm shorter than the length of the boiler combustion chamber.
Type of boiler
astra G-50
length of firewood, mm
750
The recommended thickness of the wood logs is 100-150mm. Thicker pieces of firewood should be split at least once. Up to
15% of the fuel load can consist of fine wooden splinters and sawdust. However, they must be loaded in such a way so as not
to block the opening of the ceramic burner 22 (Fig. 1) connecting the upper and lower chambers of the boiler.
Do not fire freshly prepared and excessively damp pieces of firewood. The operation of the boiler
becomes inefficient, deposits of resin emerge on its inside walls as well as excessive condensate. corrosion of
the boiler takes place several times faster when firing it with freshly prepared wood or wood that has been
dried outside for several months only!
Recommendations for firewood preparation:
• put split wood in a properly-ventilated place – if possible, in a sunlit place;
• firewood should be well sheltered from rain and snow;
• pieces of split wood should be stacked with sufficient gaps between them so that the freely-circulating air can blow away
the moisture evaporated from the pieces of firewood;
• there should be sufficient space above the heap of firewood below the roof and sufficient ventilation to remove the moist air;
• it is not advisable to store freshly-cut firewood in a basement since the firewood needs sun and free air movement to dry.
Dry wood can be stored in the basement where sufficient ventilation is guaranteed;
