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 flame,
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 flue. 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-flame burner is
installed on a hot water boiler for heating use, it must be connected so
that it works normally with both flames, completely stopping without
passing to the first flame when the preset temperature is reached. So
that it works in this way, do not install the second flame'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 first flame
(LED 5), which allows the fuel at a pressure of 12 bar to get to the first
flame's nozzle and from this to enter the combustion chamber finely
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
first flame ignition the air damper is kept in the position registered on
the screw 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 46). If the flame appears normally, with the
safety time set by the electrical equipment passed, this switches on
the solenoid valve (closed at rest) of the second flame (LED 6) (if the
air adjustment servo motor is used, see page 46). The opening of the
2nd flame 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 flame appears in the
combustion chamber the burner is controlled by the photoelectric cell
and the thermostats.
Control box and
relativ programmer
GR2
Control box specifications
Safety time
Preventilation and
in seconds
washing time
5
20
38 / 96
0006081053_200801
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 flame 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 flow. The switch
on stage is thus repeated and, if the flame ignites again normally, the
burner starts working again normally, if not (if the flame 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 first and the second flames by replacing
the nozzles.
Bear in mid however that for good working, the fuel supply with the first
flame should not be less than the minimum capacity (as indicated on the
plate) for the specific model. A lower capacity will make ignition difficult
and combustion with the first flame alone may not be good.
1 Main ON-OFF switch
2 Live voltage light
3 Fan working light
4 Transformer on light
Post-starting
in seconds
5
5 2
stage working light
nd
6 1
stage working light
st
7 Control box lock-out light
8 Control box release button
`time between
1st e 2nd flame
5
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