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Start-up, calibration and operation of the burner
6.4 Burner ignition
Once the above steps are completed, the burner should ignite.
If the motor starts but the flame does not appear and the control
box goes into lockout, reset and wait for a new ignition attempt.
If ignition does not occur, it is possible that gas is not reaching the
combustion head within the safety time period of 3 seconds.
Therefore, it is necessary to increase gas ignition delivery.
The arrival of gas to the sleeve is indicated by the U-type
pressure gauge (Fig. 24).
If the burner locks out again, refer to chapter "Faults - Possible
causes - Solutions” on page 34.
Once ignition has taken place, proceed with global calibration
operations.
6.5 Burner adjustment
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 Output upon ignition
4 Air pressure switch
5 Gas minimum pressure switch
6.5.1 Output upon ignition
According to standard EN 676:
Burners with MAX output up to 120 kW
Ignition can occur at the maximum operation output level.
Example:
• max. operation output: 120 kW
• max. output upon ignition: 120 kW
Burners with MAX output above 120 kW
Ignition must occur at a lower output than the max. operation
output.
If the ignition output does not exceed 120 kW, no calculations are
required. 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. 4 on page 12) (the burner
starts and locks out 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 given by the
formula:
Example for G 20 gas (10 kWh/Nm
3
):
Max operation output, 600 kW
corresponding to 60 Nm
3
/h.
After 10 ignitions with their lockouts, the delivery indicated on the
meter must be equal to or less than:
60: 360 = 0.166 Nm
3
.
6.5.2 Output in 2nd stage
2nd stage output must be selected within the firing rate range
indicated in page 10.
In the above description, we left the burner running, operating in
1st stage. Now move switch 2)(Fig. 25) to 2nd stage position: the
servomotor will open the air damper and, at the same time, the
gas butterfly valve at 90°.
Adjustment of gas delivery
Measure the gas delivery on the meter.
A rough indication can be obtained from tables on page 5, just
read the gas pressure on the U-shaped pressure gauge, see
Fig. 24 on page 24, and follow the instructions given in 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.
In the event the burner stops, in order to prevent
any damage to the installation, do not unblock the
burner more than twice in a row. If the burner
locks out for a third time, contact the customer
service.
In the event there are further lockouts or faults
with the burner, the maintenance interventions
must only be carried out by qualified, authorised
personnel, in accordance with the contents of this
manual and in compliance with the standards and
regulations of current laws.
Nm
3
/h
(max. burner delivery)
360
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