baltur BGN 40 DSPGN-ME Mode D'emploi page 28

DESCRIPTION OF OPERATIONS AT MODULATION FLAME (See 0002910830)
The approximate delivery variation range is, indicatively, from 1 to 1/3. Ignition is preceded by pre-ventilation of
the combustion chamber as per standards, with the air open: this lasts about 36 seconds. If, at the end of the
ventilation stage, the ventilation air pressure control switch detects that pressure is sufficient, the ignition transformer
comes on and, after 3 seconds, the safety and main valves open in sequence. The gas reaches the combustion
head, is mixed with the air being delivered by the fan, and is ignited. Delivery is regulated by the gas throttle valve.
Three seconds after the (main and safety) valves are opened the ignition transformer is switched off. The burner
is now on at the ignition point (P0). The flame is detected by the relative control device (an ionisation sensor
positioned inside the flame, or a UV photocell). The programming relay goes beyond the shutdown position and
powers the air/gas delivery regulation servomotors, which go to minimum (P1). If the modulation sensor – adjusted
by a temperature or pressure lower than that in the boiler) – allows, the air/gas delivery servomotors start running
and cause a gradual increase is the delivery of gas and combustion air until the maximum flow rates to which the
burner has been set have been reached (point P9).
N.B. Electronic cam MPA 22 controls the burner by adjusting the combustion air and gas servomotors
according to a pre-set operating curve.
The burner remains at the maximum delivery position until the temperature or pressure reaches the limit set for
the intervention of the modulation probe and makes the servomotors regulating gas/air delivery rotate in the
opposite sense of direction. Thus gas delivery and the relative combustion air are gradually reduced until they
reach minimum level. Even with delivery at a minimum, if the limit (temperature or pressure) at which the shut
down device (thermostat or pressure switch) has bee regulated is reached, the burner will be brought to a standstill.
When the temperature or pressure drops below the intervention limit set on the shut down device, the burner will
start up again, according to the programme previously described.
During normal operations, the boiler modulation probe fitted to the boiler detects the variations requested and
automatically proceeds with adapting the fuel and combustion air delivery by inserting the servomotors which
regulates delivery (gas/air). This will rotate in such a way as to obstain an increase or a decrease.
With this manoeuvre, the gas/air delivery regulating system try's to equilibrate the quantity of heat supplied to the
boiler with that which the boiler gives to be utilised. If the flame does not appear within THREE seconds of the
opening of the gas valves, the control box goes to "shut down" (the burner stops completely and the relative
indicator light is turned on). To unblock the control box, press the appropriate push-button.
DIAGRAM FOR MODULATING OR TWO-STAGE PROGRESSIVE GAS
BURNERS
1 Ball cock
2 Anti-vibration joint
3 Gas filter
4 Gas pressure regulator
5 Safety gas valve
6 Servomotor gas regulator
Gas pressure switch with pressure take-offs
7
Gas delivery modulating throttle valve
8
9 Main flame valve
Minimum gas pressure switch and gas valve
10
seal control pressure switch
11 Servomotor air regulator
12 Air pressure switch
28
N° 0002910830
REV.: 24/06/2004