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6.12
Pressure switch adjustment
6.12.1 Air pressure switch - check CO
Adjust the air pressure switch after performing all other burner
adjustments with the air pressure switch set to the start of the
scale (Fig. 39).
With the burner operating at MIN output, increase adjustment
pressure by slowly turning the relevant knob clockwise until the
burner locks out.
Then turn the knob anticlockwise by about 20% of the set point
and repeat burner start-up to ensure it is correct.
If the burner locks out again, turn the knob slightly anticlockwise.
In conformity with the standard, the air pressure
switch must prevent the air pressure falling below
80% of the adjusted value and the CO in the flue
gases exceeding 1% (10,000 ppm).
WARNING
To check this, insert a combustion analyser in the
flue, slowly reduce the burner air setting (for
example with a piece of cardboard) and verify that
the burner locks out before the CO value in the
flue gases exceeds 1%.
The air pressure switch is installed in the "absolute" position, i.e.
it is connected only to the pressure test point "+" 22)(Fig. 4).
6.12.2 Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 40) after making
all other burner adjustments with the maximum gas pressure
switch set to the end of the scale.
To calibrate the maximum gas pressure switch, open the tap and
then connect a pressure gauge to its pressure test point.
The maximum gas pressure switch must be regulated to a value
no higher than 30% of the measurement read on the gauge when
the burner is working at maximum output.
After making the adjustment, remove the pressure gauge and
close the tap.
6.12.3 Minimum gas pressure switch
Adjust the minimum gas pressure switch after performing all the
other burner adjustments with the pressure switch set to the start
of the scale (Fig. 41).
With the burner operating at maximum output, increase
adjustment pressure by slowly turning the relative knob clockwise
until the burner stops.
Then turn the knob anticlockwise by 0.2 kPa (2 mbar) and repeat
burner start-up to ensure it is operating regularly.
If the burner locks out again, turn the knob anticlockwise again by
0.1 kPa (1 mbar).
1 kPa = 10 mbar
WARNING
20148180
Start-up, calibration and operation of the burner
D3856
34
GB
D3854
Fig. 39
PA
20181543
PGM
D3855
Fig. 40
Fig. 41
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