b)
A "shutdown" when the flame is lit may be caused by the instability of the same in the ionisation
zone, due to an incorrect air/gas ratio.
This can be corrected by varying the quantity of air and/or gas delivered until the right ratio is achieved.
The same problem may be caused by an incorrect air/gas distribution in the burner head. This can be
remedied by adjusting the control in the burner head, increasing or decreasing the air passage be-
tween the head and the gas diffuser.
To carry out this operation, refer to burner head adjustment.
c)
It may occur that the ionisation current is set against the ignition transformer discharge current (the
two currents take the same route on the burner "ground"), putting the burner into the shutdown state
due to insufficient ionisation.
This is remedied by inverting the ignition transformer power supply (220V side), by cleaning the posi-
tion of the two wires that take the voltage to the transformer.
This problem can also be caused by insufficient "grounding" on the burner casing.
The minimum ionisation current value to ensure the functioning of the unit is displayed on the electrical
circuit diagram. Normally, the ionisation current is much higher.
To check the ionisation current, connect an appropriately scaled micro-ammeter "in series" with the
ionisation current. The high isolation wire coming from the electrode must be connected to the nega-
tive ( - sign ) terminal of the micro-ammeter.
5)
With the burner lit, set the delivery rate to the "first flame" to the desired level (methane = 8550 kcal/m
making the reading on the counter.
This rate can be changed by adjusting the regulator on the valve, as illustrated above.
6)
Check that the combustion occurs correctly, using the appropriate instruments (CO
for methane - max. CO = 0,01%).
7)
After making the adjustment, turn off and re-start the burner a number of times to check that it starts up
correctly.
8)
N.B.
On some burner models, the thermostat of the 2nd flame must be at 2 contacts (in exchange);
please do refer to the electric diagram of the specific burner, in case you haven't in exchange at two contacts,
please do refer to the diagram n° 0002050151.
With the burner switched off at the general switch, switch on the second flame thermostat and set it by adjust-
ing the control on the servo so that the air shutter opening is at the appropriate level for the second flame (see
BT 8914). Open the gas flow regulator on the valve to achieve the appropriate delivery rate for the second
flame (main flame).
9)
Switch off the general switch to start up the burner.
When the burner is lit, check the gas delivery rate and the combustion, using the correct instruments, as
described above. According to the results of this check, if necessary, adjust the gas delivery rate and the
combustion air delivery rate to the desired value, according to specific circumstances (boiler power). Obvi-
ously, a check should also be made on the CO
0,1%).
10)
Check the efficiency of the safety devices, shutdown (disconnecting the ionisation electrode cable), air
manostat, gas manostat and thermostats.
and CO levels (CO
= approx. 10% for methane - max. CO =
2
2
24
3
),
= approx. 10%
2