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CAPACITY OF BLACK IRON GAS PIPE (CU. FT. PER HOUR) FOR NATURAL GAS (SPECIFIC GRAVITY - 0.60)
NOMINAL
BLACK IRON
PIPE DIAMETER
(in.)
1/2
3/4
1
1 1/4
1 1/2
The cubic feet per hour listed in the table above must be greater than the cubic feet per hour of gas fl ow required
by the furnace. To determine the cubic feet per hour of gas fl ow required by the furnace, divide the input rate
of the furnace by the heating value of the gas:
Cubic Feet Per Hour Required
Table 5. Capacity of Black Iron Gas Pipe (cu. ft. per hour)
For a Natural Gas Sea Level Heating Value of 800 to 899 Btu/cu.ft.
Manifold Pressure Setting (in
WC)
For a Natural Gas Sea Level Heating Value of 900 to 999 Btu/cu.ft.
Manifold Pressure Setting (in
WC)
For a Natural Gas Sea Level Heating Value of 1,000 to 1,100 Btu/cu.ft.
Manifold Pressure Setting (in
WC)
Table 6. Manifold Pressure (in WC) for Natural Gas at Various Altitudes
For a LP Gas Sea Level Heating Value of 2,500 Btu/hr.
Manifold Pressure Setting (in
WC)
Table 7. Manifold Pressure (in WC) for LP/Propane Gas at Various Altitudes
10
20
30
130
90
75
280
190
150
520
350
285
1050
730
590
1600
1100
890
=
Heating Value of Gas (Btu/Cu. Ft.)
for Natural Gas (specifi c gravity = .60)
zero to
1999
Full Input
3.5
Low Input
1.7
zero to
1999
Full Input
3.5
Low Input
1.7
zero to
1999
Full Input
3.5
Low Input
1.7
zero to
1999
Full Input
Low Input
5.5
LENGTH OF PIPE RUN
40
50
60
65
55
50
130
115
105
245
215
195
500
440
400
760
670
610
Input To Furnace (Btu/hr)
Elevation (feet above sea level)
2000 to
5000 to
4999
5999
3.5
3.5
1.7
1.7
Elevation (feet above sea level)
2000 to
5000 to
4999
5999
3.5
3.5
1.7
1.7
Elevation (feet above sea level)
2000 to
5000 to
4999
5999
3.5
3.0
1.7
1.5
Elevation (feet above sea level)
2000 to
5000 to
4999
5999
10
8.5
10
5.5
6.5
70
80
45
40
95
90
180
170
370
350
560
530
6000 to
8000 to
7999
10000
3.5
3.0
1.7
1.6
6000 to
8000 to
7999
10000
3.2
2.8
1.6
1.5
6000 to
8000 to
7999
10000
2.8
2.5
1.4
1.3
6000 to
8000 to
7999
10000
9
8.5
6.5
6.5
23
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