Final Calibration Of The Pressure Switches; Air Pressure Switch - Co Check; Low Gas Pressure Switch - Riello RS 28/M Installation, Use And Maintenance Instructions

5.6

Final calibration of the pressure switches

5.6.1

Air pressure switch - CO check

Adjust the air pressure switch after having performed all other burn-
er adjustments with the air pressure switch set to the start of the
scale (Fig. 32).
With the burner operating, increase adjustment pressure 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
formation of CO.
To check this, insert a combustion analyser into the
WARNING
chimney, slowly close the fan suction inlet (for ex-
ample with cardboard) and check that the burner
locks out, before the CO in the fumes exceeds 400
ppm.
The air pressure switch may operate in "differential" operation in
two pipe system. If a negative pressure in the combustion chamber
during pre-purging prevents the air pressure switch from switching,
switching may be obtained by fitting a second pipe between the air
pressure switch and the suction inlet of the fan. In this way the air
pressure switch operates as differential pressure switch.
5.6.2

Low gas pressure switch

Adjust the low gas pressure switch after having performed all the
other burner adjustments with the pressure switch set at the start
of the scale (Fig. 33).
With the burner operating, increase adjustment pressure by slowly
turning the relative dial clockwise until the burner 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.
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Start-up, calibration and operation of the burner
28
Make sure that the mechanical locking systems on
the different adjustment devices are fully tightened.
WARNING
GB
D3854
Fig. 32
D9290
Fig. 33