17
ADJUSTING THE AIR AND GAS FLOW RATES
While performing the air and fuel adjustment, check the flow rate, measuring it on the counter or, if it is not possible, checking the com-
bustion head pressure by means of a differential pressure gauge as described on the next paragraph.
Combustion head pressure curves vs. the gas flow rate
Curves are referred to pressure= 0mbar in the combustion head!
The curves referred to the gas pressure in the combustion head, depending on the gas flow rate, are referred to the burner in the com-
bustion stage (percentage of residual O
2
in the flues as shown in the “Recommended combustion values” table and CO in the stan-
dard limits). During this stage, the combustion head, the gas butterfly valve and the servocontrol are at the maximum opening. Refer to
Fig. 4, showing the correct way to measure the gas pressure, considering the values of pressure in combustion chamber, surveyed by
means of the pressure gauge or taken from the boiler’s Technical specifications.
Fig. 4
Key
1
Generator
2
Pressure outlet on the combustion chamber
3
Gas pressure outlet on the butterfly valve
4
Differential pressure gauge
Measuring the gas pressure in the combustion head
In order to measure the pressure in the combustion head, insert the pressure gauge probes: one into the generator’s pressure outlet
(Fig. 4-2) to get the pressure in the combustion chamber and the other one into the butterfly valve’s pressure outlet of the burner (Fig.
4-3). On the basis of the measured differential pressure, it is possible to get the maximum flow rate: in the pressure - rate curves (sho-
wed on the next paragraph), it is easy to get the burner output in kW or Stm3/h (quoted on the x axis) from the pressure measured in
the combustion head (quoted on the y axis).
NOTE: THE PRESSURE-RATE CURVES ARE APPROXIMATE; FOR A PROPER SETTING OF THE GAS RATE, PLEASE REFER
TO THE GAS METER READING.
ATTENTION: before starting the burner up, be sure that the manual cutoff valves are open and check that the pres-
sure upstream the gas train complies the value quoted on paragraph “Technical specifications”. Be sure that the
mains switch is closed.
ATTENTION: During commissioning operations, do not let the burner operate with insufficient air flow (danger of
formation of carbon monoxide); if this should happen, make the gas decrease slowly until the normal combustion
values are achieved.
WARNING: NEVER LOOSE THE SEALED SCREWS! OTHERWISE, THE DEVICE WARRANTY WILL BE IMMEDIA-
TELY INVALIDATE!
2
4
3
1
