22
6461
GB
Start-up, calibration and operation of the burner
5
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. 30).
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
graduated 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 anticlockwise a lit-
tle bit more.
During these operations it may be useful to measure the air
pressure with a pressure gauge.
The connection of the pressure gauge is shown in Fig. 30.
The standard configuration is that with the air pressure switch
connected in absolute mode. Note the presence of a “T” con-
nection, not supplied. In certain applications in strong depres-
sion situations, the connection of the pressure switch does
not allow it to change over. In this case it is necessary to con-
nect the pressure switch in differential mode, applying a sec-
ond tube between the air pressure switch and the fan suction
line mouth. In this case also, the pressure gauge must be
connected in differential mode, as shown in Fig. 30.
Maximum gas pressure switch
Adjust the maximum gas pressure switch after having per-
formed all other burner adjustments with the maximum gas
pressure switch set to the end of the scale (Fig. 31).
With the burner operating at maximum output, lower adjust-
ment pressure by slowly turning the relative knob anticlock-
wise until the burner locks out.
Turn the knob clockwise by 2 mbar and repeat the start-up of
the burner.
If the burner locks out again, turn the knob clockwise again by
1 mbar.
Minimum gas pressure switch
Adjust the minimum gas pressure switch after having per-
formed all other burner adjustments with the pressure switch
set to the start of the scale (Fig. 32).
With the burner operating at maximum output, increase
adjustment pressure by slowly turning the relative knob clock-
wise until the burner locks out.
Then turn the knob anticlockwise by 2 mbar and repeat burner
start-up to ensure it is uniform.
If the burner locks out again, turn the knob anticlockwise
again by 1 mbar.
+
_
+
_
Connecting the pressure gauge with
the pressure switch in differential mode
D3951
Connecting the pressure gauge
with the pressure switch in abso-
lute mode
D8695
Fig. 30
Fig. 31
D3856
D3855
Fig. 32
