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DESCRIPTION OF OPERATION
When the main switch and the I/O switch (22) on the electrical
panel are closed. If the thermostats are closed, voltage will reach
the command and control device, which starts up the burner (led
19 comes on).
This turns on the fan motor for preventilation of the combustion
chamber. The ignition transformer then comes on, and 2 seconds
later the gas valves open.
Note that:
• The main valve has a device for the proportional adjustment of
the air to gas ratio.
• The safety valve is an ON/OFF type.
• The air damper is activated by an electric servo motor (see
00029336651), remember that when the burner is stopped
by the thermostat, the gate damper is brought back by the ser
vomotor to its closed position.
!
The gas supply at the ignition flame position must generally
be greater than the minimum modulation capacity. The
ignition flame position can be adjusted with the air damper
control servo motor. (see 0002933651).The presence of
the flame, detected by the control device itself, permits the
continuance and completion of the ignition stage with the
switching off of the ignition transformer. Subsequently the
servo motor progressively opens the air damper and the
pneumatic valve allows the gas supply to increase to its set
maximum.
If there is no flame, the control box stops in its “safety lock-out”
(ignition led 20) within 3 seconds from the opening of the main
valve. In the case of safety lock-out the valves immediately close
again. To release the control box from its safety position press but-
ton (21) on the display panel.
DESCRIPTION OF MODULATION WORKING
When the burner is running at minimum capacity, if the modulation
probe allows, (adjusted to a temperature or pressure value gre-
ater than that in the boiler) the air adjustment servo motor starts
to turn causing gradual increase in combustion air supply and,
consequently also of gas, up to the maximum supply for which
the burner has been set. The increase in the fan air pressure is
detected by the proportional gas valve sensor which gradually
adjusts gas supply to the change in air pressure. The burner stays
at maximum delivery until the temperature or pressure reaches a
level high enough to cause the modulation probe to turn the air
adjustment servo motor in the opposite direction.
The backward rotation and consequent reduction in gas and air
supply happens at brief time intervals. With this manoeuvre the
modulation system seeks to balance the quantity of heat supplied
to the boiler with that which the boiler itself provides. The mo-
dulation probe applied to the boiler detects changes in demand
and automatically adjusts the supply of fuel and of combustion
air, switching on the servo motor with an increased or decreased
rotation. If, even with fuel supply at minimum, the limit value is
reached (temperature or pressure) for which the device is set for
complete stop, (through thermostat or pressure switch) the burner
is stopped by the device.
By lowering the temperature or pressure again below the burner
stop device-triggering figure it is switched on again in accordance
with the program described in the previous paragraph.
Содержание TBG 45 PN
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