Pressure Switch Adjustment; Air Pressure Switch - Check Co; Gas Minimum Pressure Switch - Riello RLS 70 Manual

6.10

Pressure switch adjustment

6.10.1 Air pressure switch - check CO

Adjust the air pressure switch after performing all other burner
adjustments with the air pressure switch set to the start of the
scale (Fig. 39).
With the burner operating in 1st stage, increase adjustment
pressure by slowly turning the relevant knob clockwise until the
burner locks out.
Then turn the knob anticlockwise by about 20% of the set point
and repeat burner start-up to ensure it is correct.
If the burner locks out again, turn the knob slightly anticlockwise.
as a rule, the air pressure switch must limit the CO
in the fumes to less than 1% (10,000 ppm).
To check this, insert a combustion analyser into
ATTENTION
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 incorporated air pressure switch can work in a 'differential'
mode if connected with two pipes. If a strong depression in the
combustion chamber during the pre-purging phase does not
allow the air pressure switch to switch, this can be obtained by
applying a second tube between the air pressure switch and the
suction inlet of the fan. In this way, the pressure switch will work
in differential mode.
The use of the air pressure switch with differential
operation is allowed only in industrial applications
and where rules enable the air pressure switch to
control only fan operation without any reference to
ATTENTION
CO limit.

6.10.2 Gas minimum pressure switch

Adjust the minimum gas pressure switch (Fig. 27) after having
adjusted the burner, the gas valves and the gas train stabiliser.
With the burner operating at maximum output:
– install a pressure gauge downstream of the gas train stabilis-
er (for example at the gas pressure test point on the burner
combustion head);
– choke slowly the manual gas cock until the pressure gauge
detects a decrease in the pressure read of about 0.1 kPa
(1 mbar). In this phase, verify the CO value which must al-
ways be less than 100 mg/kWh (93 ppm).
– Increase the adjustment of the gas pressure switch until it in-
tervenes, causing the burner shutdown;
– remove the pressure gauge and close the cock of the gas
pressure test point used for the measurement;
– open completely the manual gas cock.
1 kPa = 10 mbar
ATTENTION
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Start-up, calibration and operation of the burner
34 GB
D3854
Fig. 39
D3855
Fig. 40