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the pressure itself. When the return pressure increases, there is
E
also a corresponding increase in fuel delivery. There should also
be an adequate increase in combustion air to meet the increase
N
in fuel delivery.
Adjustment can be carried out at first regulation by operating the
G
screws which vary the profile of the command disk of the combu-
stion air regulator. Fuel and combustion air delivery both increase
L
at the same time until they reach maximum value (fuel pressure
at the return pressure regulator is equal to about 18 ÷ 20 bar if
I
the pressure at the pump is at the value of 20 ÷ 22 bar). Fuel and
S
combustion air delivery remain at maximum value until the boiler
temperature (pressure, if steam boiler), approaches the value at
H
which it has been set and causes the modulation control motor
to reverse its previous sense of movement. The return movement
of the modulation motor causes a reduction in fuel delivery and a
relative reduction in combustion air.
The modulation system reaches a position of equilibrium which
corresponds to a fuel delivery and a relative combustion air delivery
Control box and re-
lative Programmer
LAL 1.25
Cyclic relay
Control box specifications
Safety Time
Pre-Ventilation & Oil
in seconds
Pre-circulation Time
in seconds
5
22,5
equal to the quantity of heat required by the boiler. With the boiler
operating, the probe in the boiler is aware of load variations in the
boiler and automatically requests the modulation motor to make an
adjustment in the fuel delivery and in the relative combustion air.
Should the maximum temperature (pressure, if steam boiler) be
reached even with fuel and combustion air delivery at a minimum,
the thermostat (pressure switch, if steam boiler) will intervene
when the value at which it has been set is reached, and bring the
burner to a standstill. When the temperature (pressure, if steam
boiler) drops below the intervention limit of the "shut down" device,
the burner will start up again as previously described. It should be
kept in mind that the field of variation in output obtainable with a
good combustion is, as an indication, from 1 to 1/3 of the maximum
output given on the rating plate.
Note: The air pressure switch must be set when the burner is started
up and must be in function with the pressure value verified
during operation with the ignition flame.
Pre-ignition Time
in seconds
2,5
10 / 28
0006081143_201107
Post-ignitio Time
Time between 1st flame &
in seconds
Start of Modulation
in seconds
5
20
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