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6.9
Spray temperature adjustment
6.9.1
Electronic adjustment thermostat
By means of information relayed from a PT 100 probe immersed
in the oil in the delivery manifold, the thermostat adjusts spray
temperature. (The correct conditions for fuel spray are shown in
the temperature/viscosity graph below).
Atomisation temperature
S7976
t Pre-heater - Delivery
Example: fuel oil with 7° E viscosity at 50° C is pre-heated to ap-
proximately 110° C.
Although the temperature set on the thermostat
should correspond to the temperature of the fluid,
it is good practice to check that the thermometer
shows the correct reading once the unit has been
ATTENTION
in operation for a few minutes. The led will illumi-
nate to indicate that the heating resistances are
working properly.
Important, only for N/M 4500.
The pre-heater fitted to the burner supplies a t of
75°C at 450 kg/h (right-hand graph).
If there is a t shortfall, this can be made up by an
auxiliary pre-heater.
Minimum temperature thermostat, in addition to shutting down
the burner if the fuel temperature should fall below the critical val-
ue for correct combustion, this thermostat also provides a permis-
sive signal at the time of burner start-up. (Factory set at
approximately 80°C, adjustable by removing the pre-heater cover
and relative plate).
Maximum temperature thermostat, this switches off the resist-
ances when, because of failure of the adjustment thermostat, the
temperature of the pre-heater increases to unacceptable levels;
20176605
Start-up, calibration and operation of the burner
Fig. 37
a "high temperature" alarm output is provided on the burner ter-
minal strip. (Factory set is approximately 180°C).
Adjustment thermostat probe
S7972
Purge
Renewing the minimum and maximum temperature thermo-
stats
Reposition the probe of the new thermostat, after having first
loosened the plate pack securing screws. Make sure that the
probe is touching the resistance and the plate pack as shown in
the adjacent figure.
The same precautions should be taken when renewing the resist-
ances in contact with the thermostat probes.
If the pre-heater should malfunction, use an ohmmeter to check
that the resistances located in contact with the temperature
probes are not burnt out (reading of approximately 35 Ohm).
Aluminium plate
S7977
Changing the PT 100 probe in the oil delivery manifold
Fit the supplied nut and biconical collar on the new probe, insert
a length of approximately 40 mm in the manifold, and secure firm-
ly into place.
At this point, the section remaining outside the manifold can be
bent as required (with no risk of damaging the resistance).
34
GB
Thermometer
Min. temperature thermostat
Pre-heater
Max. temperature thermostat
Tubes into aluminium plate
Thermostat probe
Fig. 38
Resistance
Fig. 39
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