Description Of Progressive Two-Stage Operation With Natural Gas - baltur GI MIST 350 DSPGM Manuel D'instructions Pour L'utilisation

DESCRIPTION OF PROGRESSIVE TWO-
STAGE OPERATION WITH NATURAL GAS
The term two-stage progressive operation indicates that transition
from the first to the second state (from minimum to maximum
operation) is progressive in terms of both amount of combustion air
let in and the amount of output fuel.This results in a greater pressure
stability in the gas supply network. The variation range of flow rate
is approximately 1 to 1/3.
The burner is provided with a limit micro-switch that prevents the
ignition if the flow rate regulator is not at the minimum setting. As
specified by the standards, ignition is preceded by a pre-ventilation
of the combustion chamber with open air.
If the ventilation air pressure switch detects a sufficient value of
pressure, it enables the ignition transformer after the ventilation, and
the ignition flame (pilot) and the safety valves open. Gas reaches
the combustion head, mixes with air supplied by the fan and is
ignited. The output is adjusted by the flow rate regulator integrated
in the ignition flame (pilot) valve. After the ignition and safety valve
activation, the ignition transformer is disabled. In this way, the burner
is activated with the first ignition flame (pilot) only.
The presence of the flame is detected by the control device
(ionization probe immersed in the flame, or UV cell). The
programming relay exceeds the shutdown point and powers the
fuel/air output adjustment servomotor; now the burner is operating
at the minimum flow rate.
If the 2nd stage boiler thermostat (or pressure switch) allows it
(set to a temperature or pressure higher than that in the boiler),
the fuel/air output adjustment servomotors start to turn, gradually
increasing the gas and combustion air output up to the maximum
level the burner is set to.
Cam "V" of the fuel/air output adjustment servomotor (see
8562/1) activates almost immediately when the main gas
valve completely opens. The gas output is not determined
by the main valve but by the gas supply valve (see 8816/1
and 8813/1).
The burner remains in the maximum output condition until
temperature or pressure reaches a sufficient value to trigger the
2nd stage thermostat (or pressure switch), which makes the fuel/
air output servomotor turn in the opposite direction to the previous
one, gradually reducing gas and combustion air supply to the
minimum value.
If the threshold value (temperature or pressure), to which the
complete shutdown device (thermostat or pressure switch) is set,
is reached even with minimum gas and air output, the burner will
be shut down when the device is triggered.
As temperature or pressure drops below the shutdown device's
setpoint, the burner is enabled again as described above.
During regular operation, the 2nd stage boiler thermostat (or
pressure switch) applied to the boiler detects variations in demand
and automatically adapts fuel and combustion air output, increasing
or decreasing the rotation of the fuel/air output servomotor. This
makes the air/gas output control system balance the amount of
heat supplied to the boiler, with the amount it gives off during use.
If the flame is not ignited within the safety time, the control equipment
shuts down (complete stop of burner, and switching on of relevant
warning light).
To "resume" the equipment operation press the dedicated button.
16 / 44
0006080103_201309