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5.5
Final calibration of the pressure switches
5.5.1
Air pressure switch
The air pressure switch is connected in differential (Fig. 37) and is
activated by both the negative pressure of the air intake and the air
pressure from the fan.
Adjust the air pressure switch (Fig. 36) after having performed all
other burner adjustments with the air pressure switch set to the
min. of the scale.
With the burner operating at low fire, adjust the pressure switch by
slowly turning the relative knob clockwise until the burner locks out.
Then turn the knob counter-clockwise about 20% of the set point
and start-up the burner again to ensure the set point is correct.
If the burner locks out again, turn the knob counter-clockwise a little
bit more.
5.5.2
Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 38) after having per-
formed all other burner adjustments with the maximum gas pres-
sure switch set to the end of the scale.
With the burner operating at MAX output, reduce the adjustment
pressure by slowly turning the adjustment dial anticlockwise until
the burner locks out.
Then turn the dial clockwise by 0.8" WC and repeat burner firing.
If the burner locks out again, turn the dial again clockwise by
0.4" WC.
5.5.3
Minimum gas pressure switch
Adjust the minimum gas pressure switch (Fig. 39) after having per-
formed all the other burner adjustments with the pressure switch
set at the start of the scale.
With the burner operating at MAX output, increase adjustment
pressure by slowly turning the relative dial clockwise until the burn-
er locks out.
Then turn the dial anti-clockwise by 0.8" WC and repeat burner
starting to ensure it is uniform.
If the burner locks out again, turn the dial anti-clockwise again by
0.4" WC.
Start-up, calibration and operation of the burner
31
20048352
GB
Fig. 36
D3854
Fig. 37
D9272
Fig. 38
D9290
Fig. 39
20094575
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