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5.5
Burner ignition
Having completed the checks indicated in the previous heading,
ignition of the burner should be achieved.
If the motor starts but the flame does not appear and the control
box goes into lockout, reset and wait for a new start-up attempt.
If ignition is still not achieved, it may be that gas is not reaching
the combustion head within the safety time period of 3 seconds.
In this case, increase gas ignition delivery.
5.6
Adjusting the burner
The optimum adjustment of the burner requires an analysis of
flue gases at the boiler outlet.
Adjust in sequence:
1
Burner output in 2nd stage
2
Burner output in 1st stage
3
Ignition output
4
Air pressure switch
5
Minimum gas pressure switch
5.6.1
Ignition output
According to EN 676:
Burners with MAX output up to 120 kW
Ignition can occur at the maximum operation output level. Exam-
ple:
•
max. operation output: 120 kW
•
max. ignition output:
Burners with MAX output above 120 kW
Ignition must occur at a lower output than the max. operation out-
put.
If ignition output does not exceed 120 kW, no calculations are re-
quired. If ignition output exceeds 120 kW, the regulatory standard
sets that the value be defined according to the control box safety
time "ts":
–
for "ts" = 2s, ignition output must be equal to or lower than 1/
2 of max. operation output;
–
for "ts" = 3s, ignition output must be equal to or less than 1/3
of the max. operation output.
Example:
MAX operation output of 600 kW.
Ignition output must be equal to or lower than:
•
300 kW con ts = 2s
•
200 kW con ts = 3s
In order to measure the ignition output:
–
Remove the UV sensor 29)(Fig. 5 on page 11)(the burner
comes on and goes into lockout after the safety time).
–
Perform 10 ignitions with consecutive lockouts.
–
Read the quantity of gas burned on the meter.
This quantity must be equal to or lower than the quantity giv-
en by the formula:
3
Nm
/h
(max. burner delivery)
Example for G 20 gas (10 kWh/Nm
Max operation output, 600 kW
3
corresponding to 60 Nm
/h.
20194185
Start-up, calibration and operation of the burner
120 kW
360
3
):
The arrival of gas to the pipe coupling is shown by the pressure
gauge.
Once the burner has fired, now proceed with global calibration
operations.
After 10 ignitions with their lockouts, the delivery indicated on the
meter must be equal to or less than:
5.6.2
Output in 2nd stage
The output in the 2nd stage must be selected from within the fir-
ing rate range shown on page 9.
In the above description, we left the burner running, operating in
the 1st stage.
Turn switch 2)(Fig. 28) to the 2nd stage position: the servomotor
will open the air damper and, at the same time, also the gas but-
terfly valve opens at 90.
Adjustment of gas delivery
Measure the gas delivery on the gas meter.
A rough indication can be obtained from the tables on page 5, just
read the gas pressure on the U-shaped pressure gauge, see Fig.
27 on page 24), and follow the instructions on page 20.
If delivery needs to be reduced, diminish outlet gas pressure; if it
is already very low, slightly close the VR adjustment valve.
If delivery needs to be increased, increase outlet gas pressure.
Air adjustment
Progressively adjust the end profile of cam 3)(Fig. 33) by turning
the screws 5).
Turn the screws clockwise to increase air delivery.
Turn the screws anticlockwise to reduce air delivery.
2
1
20195717
1
Servomotor
2
Cam cover
3
Variable profile cam
4
Screws for adjusting the adjustable profile
5
Screws for adjusting the end profile
6
Graduated sector for gas butterfly valve
7
Index for graduated sector 6
26
GB
3
60 : 360 = 0.166 Nm
.
4
5
3
6
7
Fig. 33
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