15
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.
To measure the pressure in the combustion chamber, as far as the IDEA series, a pressure plug is provided upstream the burner’s
blast tube.
2
4
3
1
Fan air pressure plug
Pressure plug in combustion chamber
Fig. 5
