baltur GI MIST 350 DSPGM, Инструкция

Страница: 22 / 60

22 / 61
0006080103 ed2005/10
Note: If gas fl ame detection is carried out with an ionization electrode, the shut down (with fl ame presence)
could be caused by fl ame instability in the ionization zone. This fault can be eliminated by operating
the combustion head regulator (move it backwards or forwards) until the necessary conditions to
ensure fl ame stability and suffi cient intensity and stability of the ionization current are obtained.
It could happen that the ionization current is held up by the current of the ignition transformer (the
two currents have to run the same course on the burner’s earth) and so the burner goes to “shut
down” due to insuffi cient ionization. This can be remedied by inverting the input (230 V side) of the
ignition transformer (change the places of two wires that take voltage to the transformer).
A shut down with fl ame presence could also be caused by the burner’s casing not being properly grounded.
The minimum value of the ionization current to ensure the working of the control box (LFL....) is
7 micro-amperes; normally the ionization current is decidedly higher (this value is shown on the wiring
diagram). To check the ionization current, connect a microammeter with an adequate scale “in series”
to the ionization current. The high isolation wire that comes from the electrode must be inserted to the
negative (sign -) of the microammeter.
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 passage 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 fi ngers, 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 fl ame (or cigarette lighter or a candle) or with the electric spark that occurs between electrodes in an ordi-
nary ignition transformer. To ensure that the UV cell works properly, its current value should be suffi ciently
stable so as not to fall below the minimum value required for the specifi c 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 microam-
meter, with an adequate scale, in series to one of the two UV photoelectric cell connection wires. It is obviously
necessary to respect the po 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 fl ame valve and safety valve open and servomotor which
regulates delivery (gas/air) at a minimum), immediately check visually the entity and appearance of the fl a-
me and, if necessary, proceed with correcting it by operating the gas delivery regulator of the ignition fl ame
(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 meter. 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
2
) should
increase together with the increase in delivery. As an indication, for methane gas, the percentage should be
from at least 8 % at minimum 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 modulation switches in the “MAN” (manual) and “MAX” (maxi-
mum) positions.
13) The servomotor regulating gas/air delivery starts up, the “V” cam contact closes (see BT 8562/1) and voltage
arrives at the principle gas valve which then opens. Wait until the disk on which the regulating screws have
been fi tted, 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 fl ame and
proceed, if necessary, with regulating 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 modifi ed in order to obtain the
graduality required.