baltur GI 350 DSPG Manual De Instrucciones página 37

DESCRIPTION OF OPERATIONS MODULATING
(See 8714/2)
The burner's control box (cyclic relay) is connected
by operating panel switch ( I ). The cyclic relay control box
carries out the ignition programme by starting up the fan motor
and thus the pump in order to effect the pre-ventilation and light oil
pre-circulation phases.
It is necessary that the air pressure supplied by the fan is sufficient
to cause the intervention of the relative pressure switch, if not, the
control box will go to "shut down".
Oil from the pump reaches the atomizer unit and circulates within
it because the passages leading to the outward and return nozzles
are closed. This closure is carried out by "closing pins" applied to
the ends of the rods.
These "pins" are pressed against their seats by strong springs which
are situated at the opposite ends of the rods. The oil circulates,
comes out of the atomizer unit return and arrives at the return
pressure regulator.
It passes through this and reaches the pump return and from there
it is discharged back into the return.
Oil circulation, as described above, should be carried out at a pres-
sure value slightly higher (by some bar) than the minimum pressure
at which the return pressure regulator has been set (10 ÷ 12 bar).
Duration of the pre-ventilation and oil pre-circulation phase is not
22,5 seconds, as foreseen by the control box, because it is effected
when the air shutter is in an open position. The pre-ventilation and
pre-circulation time is calculated by summing together the times of
the following manoeuvres:
- the delivery regulation servomotor's opening stroke (fuel/air)
(45 seconds) +
- pre-ventilation time foreseen by the control box (22,5 seconds) +
- the closing stroke of the delivery regulation servomotor (fuel/air)
until ignition air position (about 40 seconds).
Therefore, altogether, the duration of the pre-ventilation and oil
pre-circulation phase is about 107,5 seconds.
Subsequently, the control box continues carrying out the ignition
programme by connecting the ignition transformer which feeds the
electrodes with high voltage. The voltage between the electrodes
primes the electric spark for ignition of the fuel/air mixture.
2,5 seconds after the ignition spark appears, the control box carries
voltage to the magnet which, by means of appropriate levers, moves
backwards the two rods which intercept the flow (outward and return)
of light oil to the nozzle. This moving backwards of the rods also
determines a closing of the passage (by-pass) inside the atomizer
unit. Consequently, the pump pressure is taken to the normal value
of about 20 ÷ 22 bar.
Deviation of the two rods from the closing seat, now permits the
fuel to enter the nozzle at the pressure at which the pump has been
regulated at (20 ÷ 22 bar), and comes out of the nozzle adequately
atomized.
Control box specifications
Control box & Safety Time
relative Programmer in seconds
LAL 1.25 yclic relay 5
Pre-Ventilation & Oil Pre- Pre-ignition Time
circulation Time in seconds
22.5
9 / 24
0006080098_201109
The return pressure, which determines delivery to the furnace, is
regulated by the return pressure regulator. The value of the ignition
flow rate (minimum delivery) should be about 10 ÷ 12 bar.
The atomized light oil which comes out of the nozzle is mixed with air
supplied by the fan and is then ignited by the spark of the electrodes.
Flame presence is detected by the photoresistant cell.
The programme proceeds and, after 5 seconds, surpasses the
"shut down" position, disconnects the ignition transformer, and then
connects the delivery regulation circuit (fuel/air).
The servomotor which regulates delivery (fuel/air) commands an
increase in the delivery of fuel and combustion air at the same time.
The increase in fuel delivery is determined by a disk with a varied
profile which, by rotating, can determine a greater compression of
the return pressure regulator spring and thus an increase in the
pressure itself. When the return pressure increases, there is also a
corresponding increase in fuel delivery.
There should also be an adequate increase in combustion air to
meet the increase in fuel delivery.
Adjustment can be carried out at first regulation by operating the
screws which vary the profile of the commend disk of the combustion
air regulator.
Fuel and combustion air delivery both increase at the same time until
they reach maximum value (light oil pressure at the return pressure
regulator is equal to about 18 ÷ 20 bar if the pressure at the pump
is at the value of 20 ÷ 22 bar).
Fuel and combustion air delivery remain at maximum value until the
boiler temperature (pressure, if steam boiler), approaches the value
at which it has been set and causes the servomotor regulating fuel/
air delivery to reverse its previous sense of movement.
The return movement of the servomotor causes a gradual reduction
in light oil delivery and a relative reduction in combustion air until they
reach minimum value. Should the maximum temperature (pressure,
if steam boiler), be reached even with fuel and combustion air deli-
very at a minimum, the thermostat (pressure switch, if steam boiler)
will intervene when the value at which it has been set is reached,
and bring the burner to a standstill.
When the temperature (pressure, if steam boiler) drops below the
intervention limit of the "shut down" device, the burner will start up
again as previously described.
During normal operating conditions, the modulation probe applied to
the boiler is aware of load variations in the boiler and automatically
request the servomotor which regulates fuel/air delivery to make an
adjustment in the fuel delivery and relative combustion air delivery.
In this way, the delivery regulating system /fuel/air) reaches a position
of equilibrium which corresponds to a fuel delivery and a relative
combustion air delivery equal to the quantity of heat required by
the boiler. As in indication, it should be kept in mind that the field of
variation in output obtainable with good combustion is from 1 to 1/3
of the maximum output given on the rating plate.
Note: The air pressure switch must be set when the burner is started
up and must be in function with the pressure value verified
during operations with the ignition flame; otherwise the control
box will go to "shut down".
Post-ignition Time
in seconds in seconds
2.5 5
Time between 1st flame &
Start of Modulation in seconds
20
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