baltur COMIST 72 DSPGM Manuel D'installation, Utilisation Et Entretien page 23

Pre-ventilation is carried out with air open and, du-
!
ring this phase, the servomotor regulating the deli-
very (gas/air) is inserted and completes the whole
opening run until it reaches the "maximum" position.
Subsequently, the servomotor which regulates delive-
ry (gas/air) returns to the starting position (minimum).
Only when modulation has returned to the "minimum"
position, does the control box proceed with its ignition
programme and insert the transformer and the gas ignition
valves (pilot). During the pre-ventilation phase check that
the air pressure switch effects a changeover (it should pass
from a closed position without measurement of pressure to a
closed position with measurement of air pressure).
If the air pressure switch does not measure sufficient pressu-
re (it will not effect the changeover) and neither the ignition
transformer nor the gas ignition flame valves will be inserted
and the control box will go to "shut down". It should be poin-
ted out that "shut downs" during the first ignition phase are
considered normal. This is because air still exists in the
pipeline of the valve incline and must be expelled before it
is possible to have a stable flame. To unblock the control
box, press the relative pushbutton.
UV CELL
If the flame detection is carried out with the UV cell, the following
should be taken into consideration.
Even the slightest greasiness will compromise the pas-
sage of the ultraviolet rays through the UV photoelectric
cell bulb, thus preventing the sensitive internal element
from receiving the quantity of radiation necessary for it
to function properly. Should the bulb be fouled by light
oil, fuel oil, etc., it is indispensable to clean it thoroughly.
It should be pointed out that even by simply touching the bulb
with the fingers, it is possible to leave a slight greasiness which
could compromise the working of the UV photoelectric cell.
The UV cell does not "see" daylight or light from an ordinary
lamp. It is possible to verify its sensibility with a flame (or ciga-
rette lighter or a candle) or with the electric spark that occurs
between electrodes in an ordinary ignition transformer.
To ensure that the UV cell works properly, its current value
should be sufficiently stable so as not to fall below the minimum
value required for the specific control box. It may be necessary
to search experimentally for the best position by sliding (axial or
rotation movement) the body that contains the photoelectric cell
in respect to the fastening clamp. An inspection can be carried
out by inserting a microammeter, with an adequate scale, in
series to one of the two UV photoelectric cell connection wires.
It is obviously necessary to respect the polarity + and -). For the
LFL.... control box, the value of the cell current should be from
70 microamperes to 630 microamperes (the value is shown on
the wiring diagram).
11) With the burner operating at a minimum (ignition
flame valve and safety valve open and servomotor
which regulates delivery (gas/air) at a minimum),
immediately check visually the entity and appe-
arance of the flame and, if necessary, proceed
with correcting it by operating the gas delivery
regulator of the ignition flame (pilot) and/or the
adjustable screws of the disk which regulates
the gas and air delivery. Subsequently, check
the quantity of gas delivered by reading the me-
ter. See Chapter "Reading the meter".
If necessary, correct the gas and relative combustion
air delivery by operating as described in point 7. The
control combustion with the appropriate instruments.
For a correct air/gas ratio, the percentage of Carbon
Dioxide (CO
crease in delivery. As an indication, for methane gas,
the percentage should be from at least 8 % at mini-
mum burner delivery to an optimum value of 10 %
for maximum delivery. We advise against exceeding
the value of 10 % to avoid operating with a rather
limited excess of air which could cause (variation
in atmospheric pressure, presence of dust particles
in fan's air ducts) a considerable amount of Carbon
Monoxide (CO). It is indispensable to check, with the
appropriate instrument, that the Carbon Monoxide
(CO) present in the smoke does not exceed the
maximum level permitted of 0,1 %.
12) After having regulated at "minimum", put the modu-
lation switches in the "MAN" (manual) and "MAX"
(maximum) positions.
13) The servomotor regulating fuel/air delivery starts up;
wait until the disk on which the regulating screws
have been fitted, has reached an angle of about 12°
(this corresponds to the space taken up by three
screws), and then stop modulation and return the
switch to the "O" position. Carry out a visual control
of the flame and proceed, if necessary, with regu-
lating the combustion air and the gas by operating
the adjustable screws of the regulating disk. The
operation described above should be repeated
progressively (by moving forward the disk about 12°
at a time) and modifying every time, if necessary,
the fuel/air ratio during the whole modulation run.
Make sure that the increase in fuel delivery
occurs gradually and that maximum delivery
is reached at the end of the modulation run.
This is necessary in order to ensure that the
modulation functions with good graduality.
The positions of the screws that commend the fuel
may need to be modified in order to obtain the gra-
duality required.
14) With the burner operating at maximum delivery
required for the boiler, check combustion with the
appropriate instruments and modify, if necessary,
the previous regulation carried out after a visual
control only (CO
15) We recommend controlling the combustion with the
appropriate instruments and, if necessary, modify
the previous regulation carried out, after a visual
control only, also in a few intermediate points of the
modulation run.
16) Check that modulation functions automatically by
putting the AUT - O - MAN switch in the "AUT" posi-
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0006080115_200909
) should increase together with the in-
2
max. = 10 % CO max. = 0,1 %).
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