baltur COMIST 180 DSPNM, Инструкция, Страница: 18 / 109

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DESCRIPTION OF TWO STAGE PROGRESSIVE
OPERATIONS WITH METHANE GAS (See N°
0002910611)
We refer to a two-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
pressure. The burner’s control box (cyclic relay) is connected by
operating pane switch ( I ).
As an indication, the field of variation in output obtainable is from 1
to 1/3 of the maximum output given on the rating plate.
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 combu -
stion chamber takes place (according to Regulations).
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 the ignition flame (pilot) valves 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 one of the two ignition flame (pilot) valves.
The ignition transformer is disconnected after the pilot flame 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 thermostat or pressure switch of the 2nd stage allows it (regu -
lated 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 de -
livery (see BT 8562/1) inserts almost immediately the
principle gas valve(s), which in turn open(s) completely.
Gas delivery is not determined by the principle valve but
by the position of the gas delivery regulation valve (see
BT 8813/1).
The burner remains in the maximum delivery position until the
temperature or pressure reaches the limit set for the intervention
of the thermostat or pressure switch of the 2nd stage which 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 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 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 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.
Control box & rela -
tive Programmer
Safety
Time
in seconds
Pre-Ventilation & Oil
Pre-circulation Time
in seconds
Pre-ignition
Time
in seconds
Post-ignition
Time
in seconds
Time between
1st & 2nd flame
in seconds
LFL 1.333
Relè ciclico
3 31,5 6 3 12
CONTROL BOX SPECIFICATIONS