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0006080895 ed 2007/02
TWO-STAGE GAS BURNERS
NATURAL GAS STARTING UP AND REGULATION
(for LPG operation see the relative chapter)
In order to proceed with starting up, it’s necessary, if the burner is three-phase, to check that the sense of rotation
of the motor is correct. If not already done so at the moment of connecting the burner to the gas pipeline, it’s indi-
spensable to carry a purge of the air contained in the pipeline. As a precaution, special care should be taken and
doors and windows should be opened. Open the pipe union on the pipeline situated near the burner and then open
a little the cut-off cock (or cocks).When the characteristic odour of gas can be smelled, close the cut-off cock. Wait
until the gas present in the room has dispersed, and then reconnect the burner to the gas pipeline. Then proceed
as follows:
1) Make sure that the discharge of combustion products can take place freely (chimney lock-gates should be
open) and that there is water in the boiler.
2) Open as much as considered necessary, the combustion air regulator, (see 0002934230) and open by about
one third the air passage between the head and the fl ame disk (diffuser) see “Air regulation on combustion
Head”.
3) Operate the regulators incorporated in the gas valves in such a way as to obtain the gas delivery presumed
necessary (see 0002910311).
4) Disconnect the 2nd fl ame thermostat and give current to the burner by opening the main switch. The burners
is then turned on and carries out the pre-ventilation phase.
If the air pressure exceeds that value at which
the air pressure switch has been set,
the ignition transformer will be connected and, subsequently, the gas
valves (safety and 1
st
fl ame) will be inserted. The valves open completely and gas delivery is limited to the
position at which the fl ow regulator incorporated in the 1
st
fl ame valve has been manually regulated. At fi rst
ignition, successive “shut downs” could occur, due to the following reasons:
a - The gas pipeline has not been adequately purged of air and therefore the quantity of gas is not suffi cient
to allow for a stable fl ame.
b - A “shut down” with fl ame presence could be caused by fl ame instability in the ionisation zone, due to and
incorrect air/gas ratio. This can be remedied by varying the quantity of air and/or gas delivered, in order to
fi nd the correct ratio. It could also be caused by an incorrect distribution of air/gas in the combustion head.
This can be corrected by operating the regulation device of the combustion head by closing or opening more
the air passage between the head and the gas diffuser. See chapter “Regulation of the combustion head”.
c - It could happen that the ionisation current is help up by the current discharged from the ignition transformer
(the two currents have to run the same course on the burner’s ”earth”) and so the burner goes to “shut
down” due to insuffi cient ionisation. This can be remedied by inverting the input (230V side) of the ignition
transformer (change the places of the two wire that take voltage to the transformer). A shut down with fl ame
presence could also be caused by the burner’s casing not being properly “grounded”. We must point out that the
minimum value of the ionisation current to ensure the working of the control box is shown in the electrical
diagram; normally the ionisation current is decidedly higher. To check the ionisation current, connect a mi-
croammeter with an adequate scale “in series” to the ionisation circuit. The cable of the ionisation electrode
is equipped with a connector (see circuit diagram) to facilitate the micro-ammeter connection. The high iso-
lation wire that comes from the electrode must be inserted to the negative (sign -) of the microammeter.
5) With the burner on, adapt delivery to that desired (methane gas = 8550 kcal/m
3
) by reading the meter. Take two
readings, the second one exactly one minute after the fi rst one. The difference between the two readings schould
be multiplied by in order to obtain the fl ow per hour (60 minutes). This output can be modifi ed by operating the
special regulator incorporated in the valve (see the last pages for a desciption of how to regulate the valves).
6) Control that combustion occurs correctly by using the appropriate instruments
(CO
2
= about 10% for methane gas - CO max. = 0.1%).
7) After regulation, turn the burner off and on again several times to check that ignition occurs correctly. With the
burner disconnected from the main switch, connect the 2
nd
fl ame thermostat and regulate the special device
on the servomotor in such a way as to obtain an opening of the air shutter presumed necessary for the 2
nd
fl ame (see 0002934230). Open as well the gas fl ow regulator incorporated in the valve to allow for the correct
delivery presumed necessary for the 2
nd
fl ame (main fl ame).
8) Now close the main switch to start up the burner. When the burner has started up it is necessary to check, as
