PART III: OPERATION
29
AIR FLOW AND FUEL ADJUSTMENT
Adjustments - brief description
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Adjust the air and gas flow rates at the maximum output (“high flame”) first, by means of the air damper and the valves group
pressure stabiliser respectively.
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Check that the combustion parameters are in the suggested limits.
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Check the flow rate measuring it on the counter or, if it was not possible, verifying the combustion head pressure by means of a
differential pressure gauge, as described on par. “Measuring the gas pressure in the combustion head”.
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Then, adjust the combustion values corresponding to the points between maximum and minimum (progressive -fully modulating
burners only): set the shape of the adjusting cam foil. The adjusting cam sets the air/gas ratio in those points, regulating the
opening-closing of the air damper.
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Set, now, the low flame output, acting on the low flame microswitch of the actuator in order to avoid the low flame output increasing
too much or that the flues temperature gets too low to cause condensation in the chimney.
To change the burner setting during the testing in the plant, follows the next procedure, according to the model provided.
Adjusting the combustion head
The burner is factory-adjusted with the combustion head in the "MAX" position, accordingly to the maximum power. To operate the bur-
ner at a lower power, progressively shift back the combustion head, towards the "MIN" position, screwing the screw
VRT
. The ID index
shows how much the combustion head moved.
WARNING! During commissioning operations, do not let the burner operate with insufficient air flow (danger of
formation of carbon monoxide); if this should happen, make the fuel decrease slowly until the normal
combustion values are achieved.
WARNING! the combustion air excess must be adjusted according to the values in the following chart.
Recommended combustion parameters
Fuel
Recommended (%) CO
2
Recommended (%) O
2
Natural gas
9 ÷ 10
3 ÷ 4.8
LPG
11 ÷ 12
2.8 ÷ 4.3
Light oil
11.5 ÷ 13
2.9 ÷ 4.9
Attention! if it is necessary to change the head position, repeat the air and fuel adjustments described above.
CAUTION: perform these adjustments once the burner is turned off and cooled.
VRT
ID