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6.6.5
Air pressure switch
Adjust the air pressure switch after performing all other burner
adjustments with the air pressure switch set to the start of the
scale (Fig. 32).
With the burner operating in 1st stage, insert a combustion
analyser in the flue and slowly close the suction inlet of the
fan (e.g. with a piece of cardboard) until the CO value
exceeds 100 ppm.
Slowly turn the appropriate knob clockwise until the burner
goes into lockout.
Check the indication of the arrow pointing upwards on the
graduated scale.
Turn the knob clockwise again, until the value shown on the
graduated scale corresponds with the arrow pointing down-
wards, and so recovering the hysteresis of the pressure
switch (shown by the white mark on a blue background,
between the two arrows).
Now check the correct start-up of the burner.
If the burner locks out again, turn the knob anticlockwise a
little bit more.
During these operations it may be useful to measure the air pres-
sure with a pressure gauge.
The connection of the pressure gauge is shown in Fig. 32. The
standard configuration is that with the air pressure switch con-
nected in absolute mode. Note the presence of a "T" connection,
not supplied.
In certain applications in strong depression situations, the con-
nection of the pressure switch does not allow it to change over.
In this case it is necessary to connect the pressure switch in dif-
ferential mode, applying a second tube between the air pressure
switch and the fan suction line mouth.
The use of the air pressure switch with differential
operation is only allowed in industrial applications
and where rules enable the air pressure switch to
WARNING
merely control fan operation (without any refer-
ence to CO limits).
6.6.6
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. 33).
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 2 mbar and repeat burner
start-up to ensure it is uniform.
If the burner locks out again, turn the knob anticlockwise again by
1 mbar.
20054100
Start-up, calibration and operation of the burner
Connecting the pressure
gauge with the pressure
switch in absolute mode
+
28
GB
_
+
D8695
Connecting the pressure gauge with the
pressure switch in differential mode
D3855
_
Fig. 32
Fig. 33
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