4.13.2 Gas pressure
The adjacent diagram is used to calculate manifold pressure taking
into account combustion chamber pressure.
Gas manifold pressure measured at test point 1)(Fig. 28), with:
•
combustion chamber at 0" WC
•
burner operating at maximum output
•
Combustion head adjusted as indicated in diagram (Fig. 19)
Calculate the approximate high fire output of the burner as follows:
–
subtract the combustion chamber pressure from the gas pres-
sure measured at test point 1)(Fig. 28).
–
Find the nearest pressure value to your result in Fig. 28.
–
Read off the corresponding output on the left.
Example:
•
Maximum output operation
•
Natural gas
•
Gas pressure at test point 1)(Fig. 28)
•
Pressure in combustion chamber
5.0 - 0.79
A maximum output of 4900 MBtu/hr shown in Fig. 27 corresponds
to 4.21" WC pressure, natural gas.
This value serves as a rough guide, the effective delivery must be
measured at the gas meter.
Installation
= 5.04" WC
= 0.79" WC
= 4.21" WC
D11638
Burner output
Fig. 27
25
MBtu/h
3500
3800
4130
4430
4730
5030
5290
20097683
GB
p 1 ("WC)
p 2 ("WC)
3.65
0.6
3.7
0.7
3.8
0.9
3.9
1.0
4.05
1.1
4.25
1.3
4.29
1.4
1
2
Tab. O
Fig. 28
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