baltur BGN 17 DSPGN, Инструкция по эксплуатации

Страница: 39 / 64

39
DESCRIPTION OF OPERATIONS BGN - DSPGN (see 0002910640)
This is referred to as a 2-stage progressive operation because the passage from the 1 st flame to the 2 nd flame (from
the minimum rate to the maximum pre-established rate) takes place gradually. The amount of combustion air and fuel
delivery are increased very gradually and this ensures stabilisation of the gas feed network pressure.
The field of variation in flow obtainable is from 1 to 1/3.
The burner is fitted with an end-of-the-run switch (a micro-switch) which stops the burner starting up if the flow regulator
is not in the minimum position.
Before ignition, a pre-ventilation of the combustion chamber occurs (according to Regulations) with air open. This lasts
for about 120 seconds.
At the end of the ventilation phase, if the air ventilation pressure switch has measured sufficient pressure, the ignition
transformer will be connected and, after four seconds, the ignition flame (pilot) valves and the safety valve will open.
Gas reaches the combustion head, mixes with air supplied by the fan, and is ignited.
Delivery is regulated by the regulator incorporated in the ignition flame (pilot) valve.
The ignition transformer is disconnected two seconds after the ignition flame and safety valves are inserted. The
burner is now operating with the ignition flame (pilot) only.
Flame presence is detected by a relative control device (ionisation probe immersed in the flame, or UV Cell).
The relay programmer passes the “shut down” position and gives voltage to the servomotor which regulates the
delivery (gas/air); the burner is now operating at minimum output.
If the boiler thermostat (or pressure switch) of the 2nd stage allows it (regulated at a temperature or pressure value
superior to that existing in the boiler), the servomotor which regulates the gas/air delivery starts turning gradual increase
in the gas delivery and in the relative combustion air until it reaches the maximum delivery value at which the burner
has been regulated.
N.B. The “V” cam of the servomotor regulating gas/air delivery (see BT 8919) inserts almost immediately the
principle gas valve, which in turn opens completely.
Gas delivery is not determined by the principle valve but by the position of the gas delivery regulation valve
(see BT 8918).
The burner remains in the maximum delivery position until the temperature or pressure reaches the limit set for the
intervention of the boiler thermostat (or pressure switch) of the 2nd stage and makes the servomotor 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 value.
Even with delivery at a minimum, if the limit (temperature or pressure at the shut down device
(thermostat or pressure switch) has been 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 star
up again, according to the programme previously described.
During normal operations, the boiler thermostat (or pressure switch) of the 2nd stage fitted to the boiler detects the
variations requested and automatically proceeds with adapting the fuel and combustion air delivery by inserting the
servomotor which regulates delivery (gas/air).
This will rotate in such a way as to obtain 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 two seconds of the opening of the first flame valve (pilot), 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.