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20034293
GB
Start-up, calibration and operation of the burner
6.8
Pressure switch adjustment
6.8.1
Air pressure switch
Adjust the air pressure switch after having performed all other
burner adjustments with the air pressure switch set to the start of
the scale (Fig. 39).
With the burner working at MIN output, insert a combustion ana-
lyser in the stack, slowly close the suction inlet of the fan (for ex-
ample, with cardboard) until the CO value does not exceed 100
ppm.
Then slowly turn the appropriate knob clockwise until the burner
reaches the lockout position.
Check the indication of the arrow pointing upwards on the gradu-
ated scale (Fig. 39).
Turn the knob clockwise again, until the value shown on the grad-
uated 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 anticlockwise a little
bit more.
The incorporated air pressure switch can work in a “differential”
mode if connected with two pipes. If a negative pressure in the
combustion chamber during pre-purging prevents the air pres-
sure switch from switching. Switching may be obtained by fitting
a second pipe between the air pressure switch and the suction in-
let of the fan. In such a manner the air pressure switch operates
as differential pressure switch.
6.8.2
Maximum gas pressure switch
Adjust the maximum gas pressure switch after having performed
all the other burner adjustments with the maximum gas pressure
switch set at the end of the scale (Fig. 40).
With the burner operating at MAX output, reduce the adjustment
pressure by slowly turning the relative knob anticlockwise until
the burner locks out.
Then turn the knob clockwise by 2 mbar and repeat burner firing.
If the burner locks out again, turn the knob again clockwise by 1
mbar.
6.8.3
Minimum gas pressure switch
Adjust the minimum gas pressure switch after having performed
all the other burner adjustments with the pressure switch set at
the start of the scale (Fig. 41).
With the burner operating at MAX output, increase adjustment
pressure by slowly turning the relative knob clockwise until the
burner locks out.
Then turn the knob anti-clockwise by 2 mbar and repeat burner
starting to ensure it is uniform.
If the burner locks out again, turn the knob anti-clockwise again
by 1 mbar.
WARNING
The use of the air pressure switch with differential
operation is allowed only in industrial applications
and in places where national rules enable the air
pressure switch to control only fan operation.
Fig. 39
D3951
Fig. 40
D3856
Fig. 41
D3855
Summary of Contents for RLS 250/M
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