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27
20098687
GB
Start-up, calibration and operation of the burner
NOTE:
Once you have finished adjusting outputs MAX - MIN - INTER-
MEDIATE, check ignition once again: noise emission at this
stage must be identical to the following stage of operation. If you
notice any sign of pulsations, reduce the ignition stage delivery.
6.7
Final adjustment of the pressure switches
6.7.1
Air pressure switch
The air pressure switch (Fig. 28) is connected as in 2)(Fig. 29).
It can be connected in differential mode, see 1) (Fig. 29), i.e. it is
under pressure either by the depression or by pressure generat-
ed by the fan. In this way the burner can operate even in combus-
tion chambers in depression and with high modulation ratios: MIN
/ MAX outputs of up to 1/6.
In this case the air pressure switch needs no adjustment and its
function is limited to controlling fan operation.
Warning: The use of the air pressure switch with differential op-
eration is allowed only in industrial applications and where rules
enable the air pressure switch to control only fan operation with-
out any reference to CO limit.
Air pressure switch connected as in 2) (Fig. 29):
The air pressure switch is set after all other adjustments have
been made. Begin with the switch at the start of the scale.
With the burner operating at MIN output, increase adjustment
pressure by slowly turning the relative knob clockwise until the
burner locks out.
Then turn the knob anti-clockwise by about 20% of the set point
and repeat burner starting to ensure it is correct.
If the burner locks out again, turn the knob anticlockwise a little
bit more.
6.7.2
Minimum gas pressure switch
Adjust the minimum gas pressure switch (Fig. 30) after perform-
ing all the other burner adjustments with the pressure switch set
to the start of the scale.
With the burner operating at maximum output, increase adjust-
ment pressure by slowly turning the relative knob clockwise until
the burner locks out.
Then turn the knob anticlockwise by 0,2 kPa (2 mbar) and repeat
burner start-up to ensure it is uniform. If the burner locks out
again, turn the knob anticlockwise again by 0,1 kPa (1 mbar).
WARNING
As far as is possible, try not to move those screws
at the ends of the cam that were previously adjust-
ed for the opening of the air damper to MAX and
MIN output.
WARNING
In conformity with current standards, the air pres-
sure switch must prevent the CO in the flue gases
exceeding 1% (10,000 ppm). To check this, insert
a combustion analyser into the chimney, slowly
close the fan suction inlet (for example with card-
board) and check that the burner locks out, before
the CO in the fumes exceeds 1%.
WARNING
1 kPa = 10 mbar
Fig. 28
D521
Fig. 29
1)
2)
D794
Fig. 30
D896
Summary of Contents for 3897304
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