4.14.3 Gas Train; 4.14.4 Gas Train Installation; 4.14.5 Gas Pressure - Riello DB 2 LSE FGR Installation, Use And Maintenance Instructions

4.14.3 Gas train

Approved according to standard EN 676 and provided separately
from the burner.

4.14.4 Gas train installation

Disconnect the electrical power using the main
switch.
DANGER
Check that there are no gas leaks.
Pay attention when handling the train: danger of
crushing of limbs.
Make sure that the gas train is properly installed
by checking for any fuel leaks.
The operator must use the required equipment
during installation.
The gas train is pre-arranged to be connected to the burner at the
flange 2)(Fig. 27).

4.14.5 Gas pressure

Tab. K 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. K 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. 27), with:
• combustion chamber at 0 mbar;
• burner working at maximum modulating output;
• combustion head set as on page 26.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 27) 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. 27).
– Find, inTab. K related to the burner concerned, the pressure
value closest to the result of the subtraction.
Read the corresponding output on the left.
20169116
Installation
3 3
(8.2 Mcal/Sm )
3 3
(7.0 Mcal/Sm )
24 GB
20169803
2
1 p (mbar)
kW
G 20
1200 7
1400 8.6
1600 11.4
1800 14.6
2000 18.2
2200 22.5
2300 26
The data of thermal output and combustion
head gas pressure are related to full open (90°)
gas butterfly valve.
WARNING
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at test point 1)(Fig. 27)
Pressure in combustion chamber
A pressure of 18.2 mbar (column 1) corresponds in Tab. K to an
output of 2000 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. 27),
set the maximum modulating output required from the burner op-
eration:
– find the nearest output value in Tab. K for the burner in ques-
tion.
– read, on the right (column 1), the pressure at the test point
1)(Fig. 27).
– 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 2000 kW
Pressure in combustion chamber
18.2 + 5
pressure required at test point 1)(Fig. 27).
1
2 p (mbar)
G 25 G 20
10.5 2.7
12.9 3.1
17.1 4.2
21.9 5.3
27.3 6.5
33.8 8
39 9
= 23.2 mbar
= 5 mbar
23.2 - 5 = 18.2 mbar
= 18.2 mbar
= 5 mbar
= 23.2 mbar
Fig. 27
G 25
4
4.7
6.3
8
9.8
12
13.5
Tab. K