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5.5
Final calibration of the pressure switches
5.5.1
Air pressure switch
Adjust the air pressure switch after having performed all other bur-
ner adjustments with the air pressure switch set to the start of the
scale (Fig. 26).
With the burner operating at min. output, increase adjustment pres-
sure by slowly turning the relative dial clockwise until the burner
locks out.
Then turn the dial anti-clockwise by about 20% of the set point and
repeat burner starting to ensure it is correct.
If the burner locks out again, turn the dial anti-clockwise a little bit
more.
As a rule, the air pressure switch must prevent the
air pressure from lowering below 80% of the adjust-
ment value as well as preventing the CO in the fu-
mes from exceeding 1% (10,000 ppm).
WARNING
To check this, insert a combustion analyser into the
chimney, slowly close the fan suction inlet (for
example with cardboard) and check that the burner
locks out, before the CO in the fumes exceeds 1%.
The air pressure switch is fitted in an "absolute" mode, that is,
connected only to the pressure test point "+" 23)(Fig. 5).
5.5.2
Maximum gas pressure switch
Adjust the maximum gas pressure switch after having performed all
other burner adjustments with the maximum gas pressure switch
set to the end of the scale (Fig. 27).
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 after having performed all
the other burner adjustments with the pressure switch set at the
start of the scale (Fig. 28).
With the burner operating at MAX output, increase adjustment
pressure by slowly turning the relative dial clockwise until the bur-
ner 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.
20049577
Start-up, calibration and operation of the burner
26
GB
D3854
Fig. 26
Fig. 27
D9272
D9290
Fig. 28
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