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0006081053 - ed 2006/12
DESCRIPTION OF WORKING
N.B.
It is not advisable to have too large a
burner for the boiler for heating and for
hot water as the burner may work for long
periods with a single fl ame, making the
boiler work at lower than required output;
as a result of this the combustion products
(fumes) emerge at too low a temperature
(at about 180° C in the case of heavy oil
and 130° C with light oil), causing soot
to build up at the fl ue. In addition, when
the boiler is working at lower output than
that indicated in the technical data, it is
likely that acidic condensate and soot
will form in the boiler with the result that
it will quickly corrode and get clogged up.
When the two-fl ame burner is installed on
a hot water boiler for heating use, it must
be connected so that it works normally
with both fl ames, completely stopping
without passing to the fi rst fl ame when
the preset temperature is reached. So
that it works in this way, do not install the
second fl ame’s thermostat, and make
a direct bridge connection between the
equipment’s terminals. In this way only
the burner’s capacity to switch on at low
rate is used for a gentle ignition, which is
essential for boilers with a pressurised
combustion chamber and also very
useful for normal boilers with depression
combustion chamber.
The boiler’s start - stop is subject to the
usual running or safety thermostats.
By switching off switch 1, if the thermostats
are closed, the voltage reaches the
command and control equipment
(switching on Led 2) which starts it working.
The fan motor (LED 3) and the ignition
transformer (LED 4) are then switched on.
The motor turns the fan that carries out
an air wash of the combustion chamber
and at the same time of the fuel pump
that cause circulation in the ducts that
expels any gas bubbles through the return
valve. This pre-wash stage ends with the
opening of the safety solenoid valves and
the fi rst fl ame (LED 5), which allows the
fuel at a pressure of 12 bar to get to the
fi rst fl ame’s nozzle and from this to enter
the combustion chamber fi nely atomised.
As soon as the vaporized fuel leaves the
nozzle it is lit by the charge between the
electrodes on the start of the motor. During
fi rst fl ame ignition the air damper is kept
in the position registered on the screw
Control box specifi cations
Control box and
Safety time
Preventilation and
Post-starting
`time between
relativ programmer
in seconds
washing time
in seconds
1st e 2nd fl ame
GR2
5
20
5
5
which is accessed by unscrewing the cap
on the top of the hydraulic control piston
(see page 39), if the air adjustment servo
motor is used (see page 73). If the fl ame
appears normally, with the safety time set
by the electrical equipment passed, this
switches on the solenoid valve (closed at
rest) of the second fl ame (LED 6) (if the
air adjustment servo motor is used, see
page 73). The opening of the 2nd fl ame
allows the light oil, at a pressure of 12 bar,
to reach the 2nd nozzle and, at the same
time, the control piston for the combustion
air adjuster moves down to open the
adjuster further. The travel distance of the
piston can be registered with the screw
with locking nut, the burner is thus working
at full rate. From when the fl ame appears
in the combustion chamber the burner is
controlled by the photoelectric cell and the
thermostats.
The control equipment follows the program
and switches the ignition transformer off.
When the temperature or the pressure
in the boiler reaches that set by the
thermostat or pressure switch, the latter
stops the burner. Subsequently, when the
temperature or the pressure falls below
the closing level of that of the thermostat
or pressure switch, the burner is switched
back on again. If, for any reason, during
the working of the burner the fl ame is lost,
after just one second the photoelectric
cell reacts to cut off the power supply
from that relay to automatically switch off
the solenoid valves which intercepts the
nozzles fl ow. The switch on stage is thus
repeated and, if the fl ame ignites again
normally, the burner starts working again
normally, if not (if the fl ame is irregular or
fails to light completely) the equipment
goes automatically into lock-out (LED
7). If the program is interrupted (due to a
power supply failure, manual action or the
intervention of the thermostat, etc.) during
the pre-wash stage, the programmer
returns to its starting position and will
automatically repeat the whole of the
burner ignition sequence.
Note:
It is clear from the above that the choice of
nozzles, depending on the total capacity
(2 nozzles working) desired, must be
made taking into account the capacity
corresponding to the working pressure of
12 bar using light oil. It is of course possible
to vary within wide limits the relationship
between the fi rst and the second fl ames
by replacing the nozzles.
Bear in mid however that for good working,
the fuel supply with the fi rst fl ame should
not be less than the minimum capacity
(as indicated on the plate) for the specifi c
model. A lower capacity will make ignition
diffi cult and combustion with the fi rst fl ame
alone may not be good.
