baltur GI 350 DSPG, Instruction

Page: 39 / 84

37 / 81
0006080098_200302
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.
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 pres-
sure 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”.