Riello DB 12 LSM C13 Installation, Use And Maintenance Instructions page 63

5.14.4 Gas pressure
Tab. I indicates the pressure drops of the combustion head and
gas butterfly valve, on the basis of the burner operating output.
The values shown in Tab. I refer to:
– Natural gas G 20 NCV 9.45 kWh/Sm
– Natural gas G 25 NCV 8.13 kWh/Sm
Column 1
Combustion head pressure drop.
Gas pressure measured at test point 1)(Fig. 24), with:
• combustion chamber at 0 mbar;
• burner working at maximum modulating output;
• combustion head set as on page 18.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 24) with maximum
opening: 90°.
To calculate the approximate output at which the burner oper-
ates:
– subtract the pressure in combustion chamber from the gas
pressure measured at test point 1) (Fig. 24).
– Find, inTab. I related to the burner concerned, the pressure
value closest to the result of the subtraction.
Read the corresponding output on the left.
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at test point 1)(Fig. 24)
Pressure in combustion chamber
95.6 - 10
A pressure of 85.6 mbar (column 1) corresponds in Tab. I to an
output of 10000 kW.
This value serves as a rough guide; the effective output must be
measured at the gas meter.
To calculate the required gas pressure at test point 1) (Fig. 24),
set the maximum modulating output required from the burner op-
eration:
– find the nearest output value in Tab. I for the burner in ques-
tion.
– read, on the right (column 1), the pressure at the test point 1)
(Fig. 24).
– Add this value to the estimated pressure in combustion
chamber.
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at an output of 10000 kW
Pressure in combustion chamber
85.6 + 10
pressure required at test point 1)(Fig. 24).
Installation
3 3
(8.2 Mcal/Sm )
3 3
(7.0 Mcal/Sm )
= 95.6 mbar
= 10 mbar
= 85.6 mbar
= 85.6 mbar
= 10 mbar
= 95.6 mbar
23 GB
1 ∆ p (mbar)
kW
G 20
5500 25.9
6000 30.8
6500 36.2
7000 42.0
7500 48.2
8000 54.8
8500 61.9
9000 69.4
9500 77.3
10000 85.6
10500 94.4
11000 103.6
11500 113.2
12000 123.3
12500 133.8
5.14.5 Pilot - gas train connection
The burner is fitted with a dedicated gas train that is fixed to the
pipe coupling.
➤ It should be connected to the main train downstream the fil-
ter or the pressure adjuster (depending on configuration).
Supply pressure 68 ÷ 500 mbar.
WARNING
2 ∆ p (mbar)
G 31 G 20 G 31
12.3 2.7 1.1
14.6 3.2 1.3
17.2 3.8 1.6
19.9 4.4 1.8
22.9 5.0 2.1
26.0 5.7 2.4
29.4 6.5 2.7
32.9 7.3 3.0
36.7 8.1 3.4
40.7 9.0 3.7
44.8 9.9 4.1
49.2 10.8 4.5
53.8 11.8 4.9
58.6 12.9 5.4
63.5 14.0 5.8
20119307
Tab. I