4.10.1 Gas Train; 4.10.2 Gas Train Installation; 4.10.3 Gas Pressure - Riello DB 3 SE FGR Installation, Use And Maintenance Instructions

4.10.1 Gas train

Approved according to standard EN 676 and provided separately
from the burner.
To select the correct gas train model, refer to the supplied "Burn-
er-gas train combination" manual.

4.10.2 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 set up to be connected to the burner by the flange
2)(Fig. 14).

4.10.3 Gas pressure

Tab. H 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. H 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. 19), with:
• combustion chamber at 0 mbar;
• burner working at maximum modulating output;
• combustion head set as on page 21.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 19) 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. 19).
– Find, in Tab. H related to the burner concerned, the pressure
value closest to the result of the subtraction.
– Read off the corresponding output on the left.
20162773
Installation
3 3
(8.2 Mcal/Sm );
3 3
(7.0 Mcal/Sm ).
19 GB
20162825
1  p (mbar)
kW
G 20
1245 7,8
1500 9,4
1750 10,9
2000 12,4
2250 13,0
2500 13,7
2750 14,3
3000 15,0
3250 17,6
3500 20,2
3800 23,3
Example with natural gas G20:
Operation at maximum modulating output
Gas pressure at test point 1)(Fig. 19)
Pressure in combustion chamber
A pressure of 15 mbar, column 1, corresponds in Tab. H to an
output of 3000 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. 19),
set the maximum modulating output required from the burner op-
eration:
– find the nearest output value in Tab. H for the burner in ques-
tion.
– Read, on the right (column 1), the pressure at the test point
1)(Fig. 19).
– 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 3000 kW
Pressure in combustion chamber
pressure required at test point 1)(Fig. 19).
The data of thermal output and combustion
head gas pressure are related to full open (90°)
gas butterfly valve.
WARNING
1
2
2  p (mbar)
G 25 G 20
11,6 1,3
13,9 1,9
16,2 2,6
18,5 3,4
19,5 4,3
20,4 5,3
21,4 6,4
22,4 7,6
26,2 8,9
30,1 10,3
34,8 12,2
= 20 mbar
= 5 mbar
20 - 5 = 15 mbar
= 15 mbar
= 5 mbar
15 + 5 = 20 mbar
Fig. 19
G 25
2,0
2,8
3,9
5,0
6,4
7,9
9,5
11,3
13,3
15,4
18,2
Tab. H