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(A)
10
20
30
Gas butterfly valve opening angle [°]
(B)
Effects of the excess air reduction
Positive
Reduction of CO produced at
all output levels
CO formation peak shifts to
higher output levels
40
50
60
Negative
The flame tends to lengthen; if it comes into contact
with cold surfaces, combustion is interrupted and
there is an increase in the overall level of CO pro-
duced.
The flame root rises from the base of the chamber
"V".
At a high output level, there may be flame detection
problems because of the rising flame root.
D593
70
80
90
D9683
17
Example (according to EN 676)
MAX operation output of 600 kW.
Ignition output must be equal to or lower than:
• 300 kW with ts = 2 s;
• 200 kW with ts = 3 s.
In order to measure the ignition output:
-
Disconnect the plug-socket 7)(A)p.5 on the
ionisation probe cable (the burner starts up
and then go into lockout after the safety time
has elapsed).
-
Perform 10 ignitions with consecutive lock-
outs.
-
On the meter read the quantity of gas
burned.
This quantity must be equal to or lower than
the quantity given by the formula:
3
Nm
/h
(max. burner delivery)
360
Example (according to EN 676)
3
For G 20 gas (10 kWh/Nm
):
Max. operation output: 600 kW corresponding to
3
60 Nm
/h.
After 10 ignitions with lockouts, the delivery read
on the meter must be equal to or lower than:
3
60 : 360 = 0.166 Nm
.
2 - MAXIMUM BURNER OUTPUT
The maximum output values are included in the
table on page 3.
Gas adjustment
Measure the gas delivery at the meter.
A guideline indication can be calculated from the
tables on page 9, simply read off the gas pres-
sure on the U-type pressure gauge, see fig.
(E)p. 11, and follow the instructions on page 9.
-
If delivery needs to be reduced, diminish out-
let gas pressure and, if it is already very low,
slightly close adjustment valve VR.
-
If delivery needs to be increased, increase
outlet gas pressure.
Adjusting air delivery
Adjust the fan air gate valve by using the gradu-
ated sector 1)(A) after having loosened the nut
2)(A).
BURNER CALIBRATION
The calibration - to be performed with an appro-
priate analyser to measure the CO in the heated
room - is a compromise between the need to
minimise the emissions, to keep an acceptable
flame length, and to obtain stable ionisation cur-
rent values.
As a rule of thumb, by reducing the maximum
opening of the air damper you can obtain bene-
ficial effects for both the reduction of CO pro-
duced and the shift towards higher emission
peak outputs.
On the other hand, the flame lengthens and the
flame root rises; beyond a certain limit, this
could cause detection problems and, conse-
quentially, burner lockouts due to flame failure.
This is particularly possible when the burner
reaches maximum output.
During the calibration phase therefore, you are
strongly advised to monitor the levels of ionisa-
tion current generated with the various outputs.
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