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5.6.4
Air filter pressure switches (in case of use of air
filter)
In addition to the air pressure switch, the burner is equipped with
two additional air pressure switches (Fig. 38) used for the control
of the air filter condition.
The air pressure switch A) is the "Warning" one while the air pres-
sure switch B) is the "Safety".
The "Warning" is a warning only the "Safety" intervenes directly on
the ignition pilot preventing the opening of the pilot valve resulting
in the ignition failure and lockout (if there are no re-ignition attempts
in the event of flame loss).
The condition control of the filter's air pressure
switches is only performed during the pre-purging of
the burner.
WARNING
There are two green pilot lights 1) and 2)(Fig. 38) on the burner
shelf, which signal the correct operation of the filter.
Light 1) is "Safety" while light 2) is the "Warning". The pilot light on
indicates that the filter air pressure switch (the Warning for exam-
ple) is "armed" during pre-purge and therefore that the burner air
pressure is higher than that set on the Warning filter air pressure
switch.
The two pressure switches must be calibrated with two different
thresholds.
The value set on the "Warning" air pressure switch must be higher
than that of the "Safety".
Adjust the filter air pressure switches (Fig. 38) after performing all
other burner adjustments with the air pressure switches set to the
start of the scale.
Connect the pressure gauge as in Fig. 35 on page 30.
With the burner operating at maximum output, insert a combustion
analyser into the stack, slowly close the fan suction inlet (with card-
board for example) until the CO2 value is about 8.5%.
Measure the pressure value on the pressure gauge (this value is
the calibration value of the Warning pressure switch).
Close further the fan suction inlet until the CO2 value is about
9.5%.
Measure the pressure value on the pressure gauge (this value is
the calibration value of the Safety pressure switch).
Without the filter kit, adjust the A-B pressure switch-
es at the minimum pressure.
WARNING
Start-up, calibration and operation of the burner
31
1
2
Key (Fig. 38)
A
Filter air pressure switch (Warning air filter)
B
Filter air pressure switch (Safety air filter)
1
Indicator/Pilot light (Safety air filter)
2
Indicator/Pilot light (Warning air filter)
GB
B
A
20141512
Fig. 38
20140257
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