baltur BTG 20 LX Betriebsanleitung Seite 30

15) After adjusting the operation to the high flame (maximum) you must operate so that the air regulation
servomotor sets to the minimum to perform the control also in this position.
16) To set the air – and thus gas – regulation servomotor to the minimum, set the modulation switch to MIN.
17) When the air servomotor is set to minimum, and it is necessary to change the combustion conditions (gas/air),
see the instructions for regulating gas valves model MB-VEF...
18) It is advisable to perform the combustion control using the instruments and, if necessary, change the previous
regulation also in some intermediate points of the modulation stroke.
19) Now, check the correct automatic modulation operation.
20) The air pressure switch has the function of locking the control box if the air pressure is not correct. The
pressure switch must thus be set to start by closing the contact (a normally open contact) when air pressure in
the burner reach a sufficient value. Note that if the normally open contact does not close (insufficient air
pressure), the control box performs its cycle but the ignition transformer does not start, the gas valves do not
open and as a consequence, the burner stops in lock. To check the correct operation of the air pressure switch,
set the burner to the minimum output, increase the regulation value so as to check when it should start to
immediately "lock" the burner. Unlock the burner by pressing the special push button and restore the pressure
switch regulation to a sufficient value to detect the existing air pressure during the pre-ventilation step.
The pressure switch connection circuit provides for the automatic control; thus, the contact provided to be
closed when at rest (fan off, and thus, absence of air pressure in the burner) must implement this condition, or
the control box does not start (the burner remains off).
21) The gas pressure control switches (minimum and maximum), if installed, have the function of preventing the
burner from operating when gas pressure does not range in the expected values. From the specific function of
the pressure switches, it is evident that the minimum pressure control switch must used the contact that is
closed when it detects a higher pressure than that to which it is set, the maximum pressure control switch must
use the contact that is closed when it detects a lower pressure than that to which it is set. Therefore, the gas
maximum and minimum pressure switch regulation must be performed during the burner general test and
inspection, based on the pressure measured each time. Pressure switches are electrically connected in series;
thus, the start (intended as circuit opening) of any one of the gas pressure switches does not allow starting the
control box and thus, the burner. When the burner is operating (flame on), the start of the gas pressure switches
(circuit opening) causes the immediate shut down of the burner. Upon the general test and inspection of the
burner, it is necessary to check the correct operation of the pressure switches. By suitably acting on the
respective regulation members, make sure that the pressure switch starts (circuit opening), thus shutting down
the burner.
22) In case of UV photoelectric cell, after at least one minute from ignition extract the photoelectric cell from its
housing. When the UV photoelectric cell is extracted from its housing, it cannot "see" the ultraviolet radiation
emitted by the flame and thus, the relevant relay de-energises. The burner immediately shuts down in "lock". A
light greasiness strongly affects the passage of ultraviolet beams through the UV photoelectric cell bulb, thus
preventing the internal photosensitive element from receiving the necessary radiation for a correct operation. If
the bulb is dirty with light oil, heavy oil, etc., clean it accurately. Note that a simple finger contact can cause a
light greasiness, sufficient to impair the UV photoelectric cell operation. The UV photoelectric cell does not
"see" daylight or the light of a common candle. A possible sensibility check can be made with a flame (lighter,
candle) or with the electrical discharge occurring between the electrodes of a common ignition transformer. To
ensure a correct operation, the UV photoelectric cell current value must be sufficiently stable, and must not
decrease below the minimum value required for the specific control box. Said value is shown in the wiring
diagram. It may be necessary to experimentally search the best position by making the body containing the
photoelectric cell slide (axial or rotation movement) with respect to the fixing clamp.
23) Check the efficiency of the boiler thermostats or pressure switches (their start must shut down the burner).
30
TWO STAGE PROGRESSIVE NATURAL GAS BURNERS