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5.8
Final calibration of the pressure switches
5.8.1
Air pressure switch
For the RLAS 800 burner model, the air pressure switch is connect-
ed in absolute mode and is activated by the positive pressure from
the fan (Fig. 49).
For the RLAS 650 burner model, the air pressure switch is connect-
ed in differential mode and is activated by the positive pressure
from the fan an negative pressure from the burner air setting
(Fig. 49 and Fig. 5, page 11).
Adjust the air pressure switch (Fig. 49) after having performed all
other burner adjustments with the air pressure switch set to the
min. of the scale.
With the burner operating at low fire, adjust the pressure switch by
slowly turning the relative knob clockwise until the burner locks out.
Then turn the knob counter-clockwise about 20% of the set point
and start-up the burner again to ensure the set point is correct.
If the burner locks out again, turn the knob counter-clockwise a little
bit more.
5.8.2
Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 50) 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.
5.8.3
Minimum gas pressure switch
The purpose of the minimum gas pressure switch is to prevent the
burner from operating in an unsuitable way due to too low gas pres-
sure.
Adjust the minimum gas pressure switch (Fig. 51) after having ad-
justed 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 stabiliser
(for example at the gas pressure test point on the burner com-
bustion head);
–
choke slowly the manual gas cock until the pressure gauge de-
tects a decrease in the pressure read of about 0.1 kPa
(1 mbar). In this phase, verify the CO value which must always
be less than 100 mg/kWh (93 ppm).
–
Increase the adjustment of the gas pressure switch until it inter-
venes, causing the burner shutdown;
–
remove the pressure gauge and close the cock of the gas pres-
sure test point used for the measurement;
–
open completely the manual gas cock.
1 kPa = 10 mbar
WARNING
Start-up, calibration and operation of the burner
41
D3856
GB
D3854
Fig. 49
PA
20183681
PGM
Fig. 50
D9290
Fig. 51
20142253
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