baltur COMIST 122 DSPGM, Инструкция

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31
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 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 cigarette 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 appearance 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 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” (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 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 modified in order to obtain the graduality
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
2
max. =
10 % CO max. = 0,1 %).
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” position and
the MIN - O - MAX switch in the “O” position. In this way, modulation is activated exclusively by the automatic
command of the boiler’s probe, if the burner is a COMIST....MM (modulating) version, or on the command of the
thermostat or pressure switch of the 2nd stage, if the burner is a COMIST...DSPGN (two-stage progressive)
version. (See Chapter “Electronic Potentiality Regulator RWF ... for the modulating version).