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5.14.2 Gas pressure
Tab. O indicates the pressure drop of the combustion head and
the gas butterfly valve depending on the operating output of the
burner.
The values shown the table refer to:
–
natural gas G 20 NCV 10 kWh/Nm
–
natural gas G 25 NCV 8.6 kWh/Nm
Column 1
Combustion head pressure drop.
Gas pressure measured at test point 1)(Fig. 36), with:
•
combustion chamber at 0 mbar;
•
gas butterfly valve fully opened (90°) as in Fig. 36;
•
combustion head set as on page 25.
Column 2
Pressure loss at gas butterfly valve 2)(Fig. 36) 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. 36).
–
Find, in related to the burner concerned, the pressure value
closest to the result of the subtraction.
–
Read off the corresponding output on the left.
Example with G 20 natural gas - RLS 120/E MX:
Maximum output operation
Gas pressure at test point 1)(Fig. 36)
Pressure in combustion chamber
13.4 - 3.0
A pressure of 10.4 mbar, (column 1, corresponds in to an output
of 913 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. 36),
set the maximum modulating output required from the burner op-
eration:
–
find the nearest output value in for the burner in question.
–
Read, on the right (column 1), the pressure at the test point
1)(Fig. 36).
–
Add this value to the estimated pressure in combustion
chamber.
Example with G 20 natural gas - RLS 120/E MX:
Operation at maximum modulating output
Gas pressure at an output of 913 kW
Pressure in combustion chamber
10.4 + 3.0
pressure required at test point 1)(Fig. 36).
20121288
Installation
3
3
(8.6 Mcal/Nm
)
3
(7.4 Mcal/Nm
)
3
= 13.4 mbar
=
3.0 mbar
= 10.4 mbar
= 10.4 mbar
=
3.0 mbar
= 13.4 mbar
30
1 p (mbar)
kW
G20
200
1.6
275
1.8
349
2.3
424
3.1
498
4.1
573
5.4
647
7
722
8.9
796
11.1
871
13.5
290
1.7
394
2.5
498
3.5
601
4.8
705
6.4
809
8.2
913
10.4
1016
12.8
1120
15.5
1224
18.5
S9159
The data of thermal output and combustion
head gas pressure are related to full open (90°)
gas butterfly valve.
WARNING
WARNING
GB
2 p (mbar)
G25
G20
G25
2.2
0.4
0.6
2.5
0.4
0.6
3.2
0.5
0.7
4.3
0.6
0.8
5.7
0.7
1.0
7.6
0.8
1.1
9.8
0.9
1.3
12.5
1
1.4
15.5
1.1
1.5
18.9
1.3
1.8
2.4
0.6
0.8
3.5
0.6
0.8
4.9
0.7
1.0
6.7
0.8
1.1
9.0
0.9
1.3
11.5
1.1
1.5
14.6
1.2
1.7
17.9
1.4
2.0
21.7
1.6
2.2
25.9
1.8
2.5
Tab. O
Fig. 36
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