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0006080895 ed 2007/02
TWO-STAGE GAS BURNERS
previously shown, the gas delivery and the combustion with the appropriate instruments. When the results are
known, if necessary, proceed with varying the gas delivery and the relative combustion air in order to adapt
delivery to that required for the specifi c case (boiler potentiality). It is also necessary to check if the CO
2
and
CO values are adequate (CO
2
max. = about 10% for Methane gas and CO = 0.1%).
9) Control the effi ciency of the safety devices: the “shut down” (by detaching the ionisation electrode cable), the
air pressure switch, the gas pressure switch, the gas pressure switch and the thermostats).
N.B. The pressure switch is self-controlled and trefore it must close the contact, which is foreseen to be closed
at rest, (fan stops and consequently there is an absence of air pressure in the burner); if it does not, the
control box will not be inserted (the burner remains at as standstill). It must be specifi ed that if the contact
is not closed during working, the control box will carry out its cycle, but the ignition transformer will not be
inserted and the gas valves will not open. Consequently, the burner will go to shut down. Check that the air
pressure switch functions properly with burner operating at 1
with burner operating at 1
st
fl ame only
fl ame only, increase the regulating value
until it reaches intervention point and the burner should go to shut down. To ublock the burner, press the
special pushbutton and return the pressure switch regulator to a suffi cient value in order to measure the
air pressure existing during the pre-ventilation phase.
AIR REGULATION ON COMBUSTION HEAD
The combustion head is equipped with a regulation device, so as to open or close the air passage between disk
and head. By closing the passage, it is thus possible to obtain a high pressure upstream of the disk also for low
fl ow rates. The high air speed and turbulence allows a better penetration of the same into the fuel and therefore,
an excellent mixture and fl ame stability. It may be necessary to have a high air pressure upstream of the disk, so
as to prevent fl ame pulses. This condition is indispensable when the burner operates on pressurised combustion
chamber and/or with high heating load. From what said above it is evident that the device closing the air on the
combustion head must be set to such position as to
always
obtain, behind the disk, a very high air pressure value.
It is advisable to regulate so as to have such air closure on the head as to require the opening of the air damper
regulating the fl ow of the burner ventilator suction. Of course, this condition must only occur when the burner is
operating at the maximum desired output.
In practice, the regulation must start with the device that closes the air on the combustion head in an intermediate
position, igniting the burner for an indicative regulation as explained above.
When the
maximum desired output
is reached, correct the position of the device closing the air on the com-
bustion head by moving it forwards or backwards (0002934190) so as to have a suitable air fl ow for the output,
with suction air regulation damper sensibly open.
N.B. To facilitate the combustion head regulation, see tables (n° 0002935000 for BTG 15P, 0002934171 for
BTG 20P and 0002935180 for BTG 28P).
N.B.
Check that ignition is regular because if the controller has been moved forward, the output air speed could
be so high as to make ignition diffi cult.
In such a case, it is necessary to move backwards, degree by degree, the regulator until reaching the
position in which the ignition is regular and accept this new position as defi nitive.
COMBUSTION ADJUSTMENT
0002934190
D
DEFLECTOR DISK ADJUSTER SCREW
E
DEFLECTOR DISK POSITION INDEX
(0 = MIN 4 = MAX for BTG 15P)
(0 = MIN 3 = MAX for BTG 20P)
(0 = MIN 4 = MAX for BTG 28P)
