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5.7
Final calibration of the pressure switches
5.7.1
Air pressure switch
Adjust the air pressure switch (Fig. 48) after having performed all
other burner adjustments with the air pressure switch set to the
start of the scale.
With the burner operating at min. output, increase adjustment pres-
sure by slowly turning the relative dial clockwise until the burner
locks out.
Then turn the dial 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 dial anti-clockwise a little bit
more.
As a rule, the air pressure switch must prevent the
formation of CO. To check this, insert a combustion
analyser into the chimney, slowly close the fan suc-
WARNING
tion inlet (for example with cardboard) and check
that the burner locks out, before the CO in the
fumes exceeds 400 ppm.
To check this, insert a combustion analyser into the chimney,
slowly close the fan suction inlet (for example with cardboard)
and check that the burner locks out, before the CO in the fumes
exceeds 1%.
On RLS 300-400-500/EV FGR burners the air pressure switch
is fitted in a "differential" mode, that is, with two pipes connected
to the specific pressure test points "+" and "-" 22) and 37)(Fig. 3
at page 11).
5.7.2
Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 49) 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.
5.7.3
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. 50) 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.
20102963
Start-up, calibration and operation of the burner
44
D3854
D3856
D9290
1 kPa = 10 mbar
WARNING
GB
Fig. 48
PA
20181543
PGM
Fig. 49
Fig. 50
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