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000608042_200705
Equipment or
Safety
Preventilation
Pre-
Post
-
Opening time
time travel
time travel
programmer
time
time
ignition
ignition
1st flame valve
opening
closing
and the 2nd flame valve
damper
damper
s
s
s
s
s
s
s
LME 22.33A2
3
30
2
2
2
2
LME 22.233A2
3
30
2
2
30
30
DESCRIPTION OF WORKING
Closing switch 1, if the thermostats are
closed, the voltage reaches the com-
mand and control equipment (switching
on of LED 2) which starts it working.
The fan motor is thus switched on (LED
3) to carry out the preventilation of the
combustion chamber, at the same time
the air damper control servo motor mo-
ves to the opening position correspon-
ding to the maximum regulated power.
At the end of the preventilation stage
the air damper has to be returned to the
ignition flame position. If the pressure
control switch for the ventilation air de
-
tects sufficient pressure, the ignition
transformer goes on(LED 4) and, after
two seconds, the main gas and safety
valves open (LED 5)
Note that:
a) The main valve has a device for
the proportional adjustment of the
air to gas ratio.
b) The safety valve is an ON/OFF
type.
c) The air damper is activated by an
electric servo motor (see
00029336650), remember that
when the burner is stop ped by
the thermostat, the gate damper
is brought back by the servo motor
to its closed position.
Note: The gas supply at the ignition fla
-
me position must generally be greater
than the minimum modulation capacity.
The ignition flame position can be adju
-
sted with the air damper control servo
motor. (see 0002933650).The presence
of the flame, detected by the control de
-
vice itself, permits the continuance and
completion of the ignition stage with the
switching off of the ignition transformer.
Subsequently the servo motor progres
-
sively 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” (LED 7)
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 button 8 on the
display panel.
D E S C R I P T I O N
O F
MODULATION WORKING
When the burner is running at mini
-
mum capacity, if the modulation probe
allows, (adjusted to a temperature or
pressure value greater than that in the
boiler) the air adjustment servo motor
starts to turn causing gradual increase
in combustion air supply and, conse
-
quently also of gas, up to the maxi
-
mum supply for which the burner has
been set. The increase in the fan air
pressure is detected by the proportio
-
nal gas valve sensor which gradually
adjusts gas supply to the change in air
pressure. The burner stays at maxi
-
mum 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 manoe
-
uvre the modulation system seeks to
balance the quantity of heat supplied
to the boiler with that which the boiler
itself provides. The modulation 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 pressu
-
re again below the burner stop device-
triggering figure it is switched on again
in accordance with the program descri
-
bed in the previous paragraph.
