baltur BGN 17 DSPGN, Instructions Manual

Page: 42 / 64

42
EN
Note: If gas flame detection is carried out with an ionisation electrode, the shut down (with flame presence)
could be caused by flame instability in the ionisation zone.
This fault can be eliminated by operating the combustion head regulator (move it backwards or forwards)
until the necessary conditions to ensure flame stability and sufficient intensity and stability of the ionisation
current are obtained.
It could happen that the ionisation 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
insufficient ionisation.
This can be remedied by inverting the input (220 V. Side) of the ignition transformer (change the places of
two wires that take voltage to the transformer). A shut down with flame presence could also be caused by
the burner’s casing not being properly grounded. The minimum value of the ionisation current to ensure
the working of the control box (LGB...) is 7 micro-amperes; normally the ionisation current is decidedly
higher (this value is shown on the wiring diagram).
To check the ionisation current, connect a microammeter with an adequate scale “in series” to the ionisation
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 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 dell 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 LGB...
control box, the value of the cell current should be from 70 microamperes to 630 microamperes (the value is
shown in 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 delivery 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.
Then 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 gas/air delivery starts up, the "V" cam contact closes (see BT 8919) and voltage
arrives at the principle gas valve which then opens.
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 scews), and then stop modulation and return the switch to the "O"
position.