baltur COMIST 20 Installation, Use And Maintenance Instruction Manual page 57

OPERATION DESCRIPTION WITH GASEOUS
FUEL
Closing the ON - OFF switch, if the thermostats are closed, the voltage
reaches the command and control equipment which starts operating.
This turns on the fan motor for preventilation of the combustion
chamber.
At the end of the pre-ventilation phase, if the air ventilation control
pressure switch has found that there is sufficient pressure, the ignition
transformer will come on, and two seconds later the safety and main
gas valves will open.
In particular:
• The main valve is a slow opening single-stage valve
• The safety valve is an ON/OFF valve
The presence of the flame, detected by the control device, permits
continuation and completion of ignition, turning off the ignition
transformer.
Once the flame appears in the combustion chamber, the burner is
controlled and commanded by the flame control equipment and by
the thermostats.
The control equipment follows the program and switches the ignition
transformer off.
When the temperature or the pressure in the boiler reaches that set
by the thermostat or pressure switch, the latter stops the burner.
Subsequently, if the temperature of pressure decreases below the
lower thermostat or pressure switch threshold value, the burner will
switch on again.
Once the flame appears in the combustion chamber, the burner is
controlled and commanded by the flame control equipment and by
the thermostats.
The control equipment follows the program and switches the ignition
transformer off.
When the temperature or the pressure in the boiler reaches that set
by the thermostat or pressure switch, the latter stops the burner.
If there is no flame, the appliance shuts down in "safety lock-out"
mode within three seconds from the opening of the main valve. In
safety lock-out mode the valves are closed again immediately. To
release the equipment from this safety position, press the unlocking
button on the control panel.
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