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DESCRIPTION OF PROGRESSIVE TWO-
STAGE OPERATION
Blown air burners with electronic modulation may be used on hearths
under strong pressure or in a vacuum, according to the corresponding
operating curves.
They combine a very stable flame with total safety and high
performance.
The burner is fitted with an electronic cam controlled by a
microprocessor for intermittent operation, and for the control and
monitoring of the blown air gas burners. Electronic modulation
achieved by means of two step air gas regulation motors.
The burner is fitted with a valve tightness control device. To better
understand the operation of the electronic cam, read the specific
instructions in the manual provided carefully.
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.
Ignition is preceded by the combustion chamber pre-ventilation as set
forth by the Standards, with air open and with a duration of approx.
30 seconds.
If the air pressure switch has detected a sufficient pressure, the
ignition transformer activates at the end of the ventilation phase and
after 3 seconds the safety and main valves open in sequence.
The gas reaches the combustion head, mixes with air supplied by
the fan and is ignited. The gas output is regulated by the gas throttle
valve.
Three seconds after the valves (main and safety) activate, the ignition
transformer switches off.
Thus the burner is ignited at the ignition point.
The presence of the flame is detected by the control device (ionization
probe immersed in the flame) .
The programmer relay moves past the locking position and sends
voltage to the (air / gas) supply regulation servo motors, which go to
the minimum point (200).
If the second stage boiler thermostat (or pressure switch) allows
it (set to a temperature or pressure value higher than the existing
value in the boiler), the (air / gas) supply servo motors will start to
turn, gradually increasing gas and combustion air supplies up to the
maximum supply to which the burner has been set (999).
CAUTION / WARNING
The electronic cam controls the burner, activating the
combustion air, gas servomotor and the fan motor, if the
inverter is fitted, according to a curve that has ten points set
(see curve regulation table).
The burner remains in the maximum output position as long as the
temperature or pressure reaches a value sufficient enough to cause
the intervention of the probe that rotates the gas/air flow rate regulation
servomotors. This progressively reduces the gas, combustion air and
motor's RPM (if the inverter is fitted) to the minimum.
If the threshold value (temperature or pressure), to which the complete
shut-down 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 the temperature or pressure drops below the shut-down device's
(thermostat or pressure switch) set point, the burner will be turned on
again as described above.
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