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5.6.2
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. 31) 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
5.7
Flame signal measurement
Check the flame signal through the parameter 954, as indicated in
Fig. 32. The displayed value is expressed in percentage.
For further and specific information, please refer to the specific in-
struction manual.
The value during the operation must be higher than 24%. If at the
burner start-up the value is higher or equal of 18%, the burner locks
out due to the extraneous light.
The display (Fig. 32) shows parameter 954: flashing on the left. On
the right, the flame's intensity is displayed as a percentage.
Example: 954: 0.0
5.8
Final checks (with the burner working)
Open the control limit operation
Open the high limit operation
Rotate the maximum gas pressure switch knob to the mini-
mum end-of-scale position (if installed)
Rotate the air pressure switch knob to the maximum end of
scale position
Switch off the burner and disconnect the voltage
Disconnect the minimum gas pressure switch
Cover the UV flame sensor
Make sure that the mechanical locking systems on
the different adjustment devices are fully tightened.
WARNING
Start-up, calibration and operation of the burner
25
D9290
S8171
The burner must stop
The burner must stop in lockout
The burner must not start
The burner must stop in lockout due to firing failure
GB
P
V
h min s
%
Fig. 31
Fig. 32
Tab. K
20026767
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