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7.7.4
Intermediate outputs
Adjustment of gas delivery
No adjustment of gas delivery is required
Adjustment of air delivery
Press the key 2)(Fig. 35 at page 28) "output increase" a little so
that the servomotor turns by about 15°.
Adjust the screws until optimal combustion is obtained. Proceed
in the same way with the other screws.
Take care that the cam profile variation is progres-
sive.
WARNING
Switch off the burner using switch 1)(Fig. 35 at page 28), at
OFF position;
disengage the cam 4)(Fig. 36) from the servomotor, by
pressing the button 3)(Fig. 37);
moving it to the right, and check more than once that the
movement is soft and smooth, and does not grip, by rotating
the cam 4) forward and backward by hand.
Engage the cam 4) to the servomotor again by moving the
button 2)(Fig. 37) to the left.
As far as is possible, try not to move those screws at the
ends of the cam that were previously adjusted for the open-
ing of the air gate to MAX and MIN output.
Finally fix the adjustment by turning the screws 6)(Fig. 36).
N.B.
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 de-
livery.
7.7.5
Air pressure switch
Adjust the air pressure switch after having performed all other
burner adjustments with the air pressure switch set to the start of
the scale (Fig. 38).
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 anti-clockwise a little
bit more.
As a rule, the air pressure switch must prevent the
air pressure from lowering below 80% of the ad-
justment value as well as preventing the CO in the
fumes from exceeding 1% (10,000 ppm).
WARNING
To check this, insert a combustion analyser into
the chimney, slowly close the fan suction inlet (for
example with cardboard) and check that the burn-
er locks out, before the CO in the fumes exceeds
1%.
The air pressure switch is of the differential type. If a negative
pressure in the combustion chamber during pre-purging prevents
the air pressure switch from closing, fit a tube between the air
pressure switch and the suction inlet of the fan.
The use of the air pressure switch with differential
operation is allowed only in industrial applications
and in places where national rules enable the air
WARNING
pressure switch to control only fan operation.
20035573
Start-up, calibration and operation of the burner
7.7.6
Maximum gas pressure switch
Adjust the maximum gas pressure switch after having performed
all the other burner adjustments with the maximum gas pressure
switch set at the end of the scale (Fig. 39).
With the burner operating at MAX output, reduce the adjustment
pressure by slowly turning the relative knob anticlockwise until
the burner locks out.
Then turn the knob clockwise by 2 mbar and repeat burner firing.
If the burner locks out again, turn the knob again clockwise by 1
mbar.
7.7.7
Minimum gas pressure switch
Adjust the minimum gas pressure switch after having performed
all the other burner adjustments with the pressure switch set at
the start of the scale (Fig. 40).
With the burner operating at MAX output, increase adjustment
pressure by slowly turning the relative knob clockwise until the
burner locks out.
Then turn the knob anti-clockwise by 2 mbar and repeat burner
starting to ensure it is uniform.
If the burner locks out again, turn the knob anti-clockwise again
by 1 mbar.
30
GB
D521
D66
D896
Fig. 38
Fig. 39
Fig. 40
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