Minimum Output; Final Calibration Of The Pressure Switches; Air Pressure Switch - Riello RS 68/EV O2 ULX Installation, Use And Maintenance Instructions

Indication for the burner ignition
In Tab. N the calibrations of the air and gas servomotors at the
ignition point for each model are summarized according to the
change of the maximum burnt power.
Ignition point - RS 68 ULX -
Maximum power input (kW)
Gas motor/butterfly setting
Air servomotor/damper setting
Ignition point - RS 120 ULX -
Maximum power input (kW)
Gas motor/butterfly setting
Air servomotor/damper setting
Ignition point - RS 160 ULX -
Maximum power input (kW)
Gas motor/butterfly setting
Air servomotor/damper setting
Ignition point - RS 200 ULX -
Maximum power input (kW)
Gas motor/butterfly setting
Air servomotor/damper setting
5.5

Final calibration of the pressure switches

5.5.1

Air pressure switch

Adjust the air pressure switch (Fig. 34) after having performed all
other burner adjustments with the air pressure switch set to the
start of the scale.
With the burner working at MIN output, insert a combustion
analyser in the stack, slowly close the suction inlet of the fan (for
example, with a piece of cardboard) until the CO value does not
exceed 100 ppm.
Slowly turn the appropriate knob clockwise until the burner goes
into lockout.
Check the indication of the arrow pointing upwards on the gradu-
ated scale. Turn the knob clockwise again, until the value shown
on the graduated scale corresponds with the arrow pointing
downwards, and so recovering the hysteresis of the pressure
switch (shown by the white mark on a blue background, between
the two arrows).
Now check the correct start-up of the burner. If the burner locks
out again, turn the knob slightly anticlockwise. During these op-
erations it may be useful to measure the air pressure with a pres-
sure gauge.
The connection of the pressure gauge is shown in Fig. 34.
The standard configuration is that with the air pressure switch
connected in absolute mode. Note the presence of a "T" connec-
tion, not supplied.
In certain applications in strong depression situations, the con-
nection of the pressure switch does not allow it to change over.
In this case it is necessary to connect the pressure switch in dif-
ferential mode, applying a second tube between the air pressure
switch and the fan suction line mouth.
In this case also, the pressure gauge must be connected in differ-
ential mode, as shown in Fig. 34.
20205796
Start-up, calibration and operation of the burner
1050 800 350
8° 8° 10°
20° 18° 15°
1450 1030 560
6° 7° 10°
14° 14° 15°
1950 1650 950
1° 1° 10°
1° 1°
2400 1910 1350
10° 10° 10°
3° 3°
Tab. N
To determine the calibrations to use at the first start, proceed as
follows:
1 Determine the maximum power required by the burner.
2 Open the combustion head as indicated in Fig. 21 on
page 24.
3 Calculate the pressure required downstream of the gas
train: this value is given by the sum of the boiler back pres-
sure at the maximum burnt power and the pressure drop
read on the diagrams of Fig. 25, Fig. 26, Fig. 27 and Fig. 28
on page 29.
4 Set the air and gas servomotors as suggested in Tab. N. If
the maximum power falls between two indicated values,
take an intermediate value between the two according to the
opening degrees of the air and gas servomotors.
At the first ignition it is not recommended to
use an air servomotor setting that exceeds the
suggested setting by 10% .
WARNING
2°
5.4.6

Minimum output

The MIN output must be set within the firing rate (Fig. 5 on
page 10).
2°
Connecting the pressure gauge
with the pressure switch in
absolute mode
Connecting the pressure gauge
with the pressure switch in
differential mode
36 GB
D3951
+
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20209377
+
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Fig. 34