baltur COMIST 72 DSPGM Manuel D'installation, Utilisation Et Entretien page 19

DESCRIPTION OF TWO STAGE PROGRESSIVE
OPERATION WITH NATURAL GAS FOR
COMIST.....DSPGM (see N° 0002910611)
This is referred to as a 2-stage progressive operation because the
passage from the 1st flame to the 2nd 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 ensure stabilization of the gas feed network pres-
sure. 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.
At the end of the ventilation phase, if the air ventilation pressure
switch has measured sufficient pressure, the ignition transformer
will be connected and subsequently the ignition (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 flow regulator incorporated in the igni-
tion flame (pilot) valve. The ignition transformer is disconnected 3
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 (ionization
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 2
(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 air/gas delivery
(see BT 8562/1) 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
8816/1 and BT 8813/1).
Control box &
Safety time
relative Pro-
in seconds
grammer
LFL 1.333
3
Cyclic relay
The burner remains in the maximum delivery position until the tem-
perature or pressure reaches the limit set for the intervention of the
boiler thermostat (or pressure switch) of the 2
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 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 thermostat/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 to equilibrate the quantity of heat supplied to the boiler
with that which the boiler gives to be utilized.
If the flame 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 pushbutton.
stage allows it
nd
Control box specifications
Pre-Ventilation & Oil Pre-ignition
Pre-circulation Time
in seconds in seconds
31,5
15 / 30
0006080115_200909
Post-ignition
Time Time
in seconds
6 3
E
stage and makes
nd
N
G
L
I
S
H
Time between
1st flame & Start of
Modulation
in seconds
12