baltur BT 250 DSG Mode D'emploi page 31

AIR REGULATION ON THE COMBUSTION HEAD (See BT 8608/1)
The combustion head is fitted with a regulating device which closes (by moving forwards) and opens
(by moving backwards) the air passage between the disk and the head.
By closing the passage it is possible to achieve high pressure upstream the disk for low outputs as well. High
velocity and air turbulence ensure a better penetration in the fuel, an optimum mixture and good flame stability. It
might be necessary to have high air pressure upstream the disk in order to avoid flame pulsation's and it is
considered practically indispensable when the burner is operating with a pressurized furnace and/or high thermal
load. It is evident from the above, that the device which closes the air on the combustion head should be put in
such a position as to always obtain a decidedly high air pressure value behind the disk.
It is advisable to regulate in such a way as to achieve a closing of the air on the head; this will necessitate a
considerable opening of the air shutter which regulates the flow to the burner's fan suction. Obviously these
adjustments should be carried out when the burner is operating at maximum delivery desired. In practice, start
regulating by putting the device which closes the air on the combustion head in an intermediate position, start up
the burner and make trial adjustments as previously described.
When maximum delivery required has been reached, proceed with correcting the position of the device which
closes the air on the combustion head; move it backwards or forwards in such a way as to obtain an air flow
suitable for the delivery, with the air regulation shutter in suction considerably open. When reducing the air passage
on the combustion head, avoid closing it completely. Proceed with perfect centering with respect to the disk. It
must be pointed out that, if perfect centering with respect to the disk is not obtained, bad combustion and excessive
heating of the head could occur which would result in its rapid deterioration. A control can be carried out by
looking through the spy hole situated at the back of the burner; then tighten home the screws that lock the
position of the air regulation device on the combustion head.
Note: Check that ignition occurs regularly, because when the device has been moved forwards, it could occur that
the air velocity in exit is so high as to render ignition difficult. If this happens, move it backwards, gradually,
until it reaches the correct position and ignition occurs regularly. This position should be definitive.
It is better to keep the amount of air for the 1st flame to the bare minimum if a fail-safe ignition is to be achieved
also under the most critical conditions.
CHECKS
After starting up the burner, check the safety devices (photoresistant cell, shut down system, thermostats).
1) The photoresistant cell is the flame control device and, if the flame should be extinguished during operations,
it must be capable of intervening (this check should be made at least one minute after start up).
2) The burner should be capable of blocking itself (shut down), and remaining so, when the flame does not
appear regularly during the starting phase within the time limit pre-set on the control box. The shut down
causes the immediate arrest of the motor and therefore the burner and the red warning light is turned on. To
check the efficiency of the photoresistant cell and of the shut down system, proceed as follows:
a) Start up the burner.
b) About one minute after ignition, extract the photoresistant cell by pulling it out of its seat and simulate flame
failure (using a rag to close the window in the photoresistant cell support). The burner flame should be
extinguished.
c) Keep the photoresistant cell in the dark and the burner will start up again but, as the photoresistant cell does
not see the light, the burner will go to shut down within the time pre-set by the programmer. The control box
can only be unblocked by pressing manually on the appropriate push-button. Check the shut down efficiency
at least twice.
3) To check thermostat efficiency, run the burner until the water in the tank reaches a temperature of at least
50 °C. Then turn the thermostat control knob, to lower the water temperature, until an opening click is heard
which causes the burner to stop. The thermostat should trip within a maximum tolerance of 5 to 10 °C in
respect to the control thermostat (boiler thermostat); if not, change the setting on the thermostat scale to
match that of the thermometer.
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