baltur GI MIST 350 DSPGM, Instruction

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0006080103 ed2005/10

DESCRIPTION OF MODULATING  OPERATIONS WITH NATURAL GAS FOR 

(see N° 0002910611)

Control box specifi cations

The fi eld of variation in fl ow obtainable is from 1 to 1/3.

The burner is fi tted with an end-of-the-run switch (a micro-switch) which stops the burner starting up 

if the fl ow regulator is not in the minimum position.

Before ignition, a pre-ventilation of the combustion chamber occurs (according to Regulations) with air open.   

At the end of the ventilation phase, if the air ventilation pressure switch has measured suffi cient pressure, the 

ignition transformer will be connected and after  the ignition fl ame (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 fl ow regulator incorporated in the ignition fl ame (pilot) valve.

The ignition transformer is disconnected after the ignition fl ame and safety valves are inserted.

The burner is now operating with the ignition fl ame (pilot) only.

Flame presence is detected by a relative control device (ionization probe immersed in the fl ame, 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 modulation probe 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 and determines a 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 8562/1)

inserts almost immediately the principle gas valve, which in turn opens completely.   Gas delivery is not de-

termined by the principle valve but by the position of the gas delivery regulation valve (see BT 8814).

The burner remains in the maximum delivery position until the temperature or pressure reaches the limit set 

for the intervention of the modulation probe 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 level.

Even with delivery at a minimum, if the limit (temperature or pressure) at which 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 

start up again, according to the programme previously described.

During normal operations, the boiler modulation probe fi tted 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 tries to equilibrate the quantity of heat supplied to 

the boiler with that which the boiler gives to be utilized.

If the fl ame does not appear 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. 

Control box & 

relative 

Programmer

LFL 1.333

Cyclic relay

Safety Time 

in seconds

3

Pre-Ventilation 

Time with shut-

ter open

in seconds

        31,5 

Pre-ignition 

Time

in seconds

6

Post-ignition

Time

in seconds

3

Time between

1st fl ame & Start of 

Modulation 

in seconds

12