Control Box Specifications - baltur COMIST 72 DSPGM Manuel D'installation, Utilisation Et Entretien

DESCRIPTION OF TWO STAGE PROGRESSIVE
E
OPERATIONS WITH LIGHT OIL COMIST...DSPGM
N (See BT 8714/2)
G
This is referred to as a 2-stage progressive operation because the
passage from the 1st flame to the 2nd flame (from the minimum rate
L
to the maximum pre-established rate) takes place gradually both as
delivery of combustion air and of fuel. The burner's control box (cyclic
I
relay) is connected by operating panel switch ( I ).
The cyclic relay control box carries out the ignition programme by
S
starting up the fan motor and thus the pump in order to effect the
H 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
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) +
- preventilation time foreseen by the control box +
- the closing stroke of the delivery regulation servomotor (fuel/air)
until ignition air position.
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. After
the insertion 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 determi-
nes 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 the closing seat, now permits the fuel to en-
ter 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 &
relative Pro-
grammer
LFL 1.333
Cyclic relay

Control box specifications

Safety time Pre-Ventilation & Oil
Pre-circulation Time
in seconds
in seconds
3 31,5
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 photocell UV.
The programme proceeds and surpasses the "shut down" position,
disconnects the ignition transformer and by this point on the burner
is operating at minimum output. If the boiler thermostat (or pressure
switch) of the 2nd stage allows it (regulated at a temperature or
pressure value superior to that existing in the boiler), the servo-
motor which regulates the delivery starts turning and determines a
gradual increase in the fuel delivery and in the relative combustion
air until it reaches the maximum delivery value at which the burner
has been regulated. 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). The burner remains in
the maximum delivery position until the temperature or pressure
reaches the limit set for the intervention of the boiler thermostat
(or pressure switch) of the 2nd stage and makes the servomotor
regulating fuel/air delivery rotate in the opposite sense of direction,
a causing gradual reduction in fuel delivery and a relative reduc-
tion in combustion air until they reach minimum value. Should the
maximum temperature (pressure, if steam boiler), be reached even
with fuel and combustion air delivery 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 operations, the boiler thermostat / pressure switch
of the 2nd stage fitted to the boiler detects the variations requested
and automatically proceeds with adapting the fuel and combustion
air delivery by inserting the servomotor which regulates delivery
(fuel/air). This will rotate in such a way as to obtain an increase
or a decrease. 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.
Pre-ignition
Time
in seconds
6
12 / 30
0006080115_200909
Post-ignition Time between
Time 1st flame & Start of
in seconds Modulation
in seconds
3 12