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6.9
Commissioning of flue gas recirculation system
The purpose of the flue gas recirculation function is to reduce the
amount of NOx contained in the flue gas. For this purpose, part
of the flue gas is fed back into the combustion chamber, resulting
in a temperature drop.
The amount of recirculated flue gas is set via channel 3 of the
actuator.
During adjustment, bear in mind that excessive
amounts of recirculated flue gas can cause the
flame to rise above the burner head (flame
WARNING
stability limit).
NOTE:
Reducing the maximum burner output
The use of the flue gas recirculation (FGR) function or the
introduction of the flue gas mass into the supply air duct could
reduce the maximum burner output.
This means that the maximum amount of combustion air that can
be supplied will be reduced.
Therefore it is necessary to reduce the amount of fuel for high-
speed operation to ensure correct combustion values.
The control box supports the flue gas recirculation (FGR)
function, without temperature compensation.
With these operating principles, the positions of channel 3 of FGR
actuator can only vary between CLOSED (ignition position) and
the positions on the ratio control curves.
First configuration
Commissioning of the system without influence from flue gas
recirculation.
This allows adjusting the fuel/air ratio control system as if it were
operating without flue gas recirculation.
When the settings for fuel/air ratio control curves without flue gas
recirculation have been completed, it is possible to move to the
settings with a channel 3 of FGR actuator.
6.10
Steady state operation
Once the start-up cycle is completed, the burner modulation
command moves on to the thermostat/pressure switch that
controls the pressure or the temperature in the boiler.
If the temperature or the pressure is low, the burner
progressively increases the output up to the MAX value.
If then the temperature or the pressure increases, the burner
progressively lowers the output to the MIN value. And so on.
The burner stops when the heat request is less than the heat
supplied by the burner at MIN output.
The thermostat/pressure switch TL opens, the control box
carries out the switching off phase.
The air damper closes completely to reduce heat losses to a
minimum.
20171664
E-display control
Since this may affect the combustion settings, the fuel and air
adjustment actuators may need to be readjusted.
First FGR configuration
Channel 3 of the FGR actuator is kept in the ON position until an
adjustable time is reached.
During operation, check the temperature value of flue gas
recirculation (FGR). It must be equal to 100-130 °C to reduce
condensate in the burner or in the intake duct.
Configuration of FGR operation
Channel 3 of the FGR actuator is kept in the ON position until an
adjustable delay time is reached.
When starting the flue gas recirculation (FGR) for the first time,
we recommend setting the FGR delay time of the control box.
Use a value between 5 and 15 minutes.
Make sure that the flue gas temperature reaches the value within
the set time.
If necessary, the FGR temperature of the control box can be
adjusted with a start value.
In this case, an LCM regulator kit and the FGR probe kit must be
installed.
–
Factory setting time (default): 300 sec.
–
FGR default temperature: 50° C
WARNING
38
GB
Check the air temperature when the flame sensor
is fitted. If the temperature exceeds 50-60°C, the
flame sensor could be damaged.
During
burner
operation
recirculation, a high temperature may be reached.
with
flue
gas
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