Riello DB3 SM C03 Installation, Use And Maintenance Instructions page 53

5.6 Pressure switches setting
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. 27).
With the burner operating at max. output, increase adjustment pressure by slowly turning
the relative knob clockwise until the burner locks out. Then turn the knob 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 knob anticlockvise a little bit more.
Attention: 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 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%.
Maximum gas pressure switch
Adjust the maximum gas pressure switch (Fig. 28) after making all other burner adjust-
ments with the maximum gas pressure switch set to the end of the scale.
To calibrate the maximum gas pressure switch, open the tap and then connect a pressure
gauge to its pressure test point.
The maximum gas pressure switch must be regulated to a value no higher than 30% of
the measurement read on the gauge when the burner is working at maximum output.
After making the adjustment, remove the pressure gauge and close the lap.
Minimum gas pressure switch
The purpose of the minimum gas pressure switch is to prevent the burner from operating
in an unsuitable way due to too low gas pressure.
Adjust the minimum gas pressure switch (Fig. 29) 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 stabiliser (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 always be less than 100 mg/kWh (93 ppm).
– Increase the adjustment of the gas pressure switch until it intervenes, 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
Final checks
Before leaving the plant:
- ensure the adjustment and safety devices work correctly;
- check all the mechanical blocking systems on the adjustment devices are tightly
closed.
5
CHAPTER Preparation for start up
20183681
D3856
D3571
D2215
Fig. 27
PA
PGM
Fig. 28
Fig. 29
23