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Start-up, calibration and operation of the burner
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. 30).
With the burner working at MIN output, insert a combustion
analyser in the stack, slowly close the suction inlet of the fan
(for example, with a piece of cardboard) until the CO value
does not exceed 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 downwards, 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 lit-
tle bit more.
During these operations it may be useful to measure the air
pressure with a pressure gauge.
The connection of the pressure gauge is shown in Fig. 30.
The standard configuration is that with the air pressure switch
connected in absolute mode. Note the presence of a "T" con-
nection, not supplied. In certain applications in strong depres-
sion situations, the connection of the pressure switch does
not allow it to change over. In this case it is necessary to con-
nect the pressure switch in differential mode, applying a sec-
ond tube between the air pressure switch and the fan suction
line mouth. In this case also, the pressure gauge must be
connected in differential mode, as shown in Fig. 30.
Connecting the pressure gauge
with the pressure switch in abso-
lute mode
+
_
D8695
Fig. 30
20133205
D3951
+
_
Connecting the pressure gauge with
the pressure switch in differential mode
Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 31) 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.
20181543
D3856
Minimum gas pressure switch
Adjust the minimum gas pressure switch (Fig. 32) after having
adjusted the burner, the gas valves and the gas train stabiliser.
With the burner operating at maximum output:
–
install a pressure gauge downstream of the gas train stabilis-
er (for example at the gas pressure test point on the burner
combustion head);
–
choke slowly the manual gas cock until the pressure gauge
detects a decrease in the pressure read of about 0.1 kPa
(1 mbar). In this phase, verify the CO value which must al-
ways be less than 100 mg/kWh (93 ppm).
–
Increase the adjustment of the gas pressure switch until it in-
tervenes, causing the burner shutdown;
–
remove the pressure gauge and close the cock of the gas
pressure test point used for the measurement;
–
open completely the manual gas cock.
D3855
1 kPa = 10 mbar
WARNING
22
GB
PA
PGM
Fig. 31
Fig. 32
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