Filter
Top Products
29
Table 7. Capacity of Black Iron Gas Pipe (cu. ft. per hour)
for Natural Gas (specifi c gravity = .60)
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 = Input To Furnace (Btu/hr)
Heating Value of Gas (Btu/Cu. Ft.)
Table 8. Manifold Pressure (in WC) for Natural Gas at Various Altitudes
Table 10. Natural and LP Gas Orifi ce Sizes
for Elevations between zero and
4999 ft. Above Sea Level
Table 11. Natural and LP gas Orifi ce Sizes
for Elevations between 5000 and 10,000 ft.
Above Sea Level
CAPACITY OF BLACK IRON GAS PIPE (CU. FT. PER HOUR)
FOR NATURAL GAS (SPECIFIC GRAVITY = 0.60)
NOMINAL
BLACK IRON
PIPE DIAMETER
LENGTH OF PIPE RUN
(feet)
10 20 30 40 50 60 70 80
1/2 130 90 75 65 55 50 45 40
3/4 280 190 150 130 115 105 95 90
1 520 350 285 245 215 195 180 170
1 1/4 1050 730 590 500 440 400 370 350
1 1/2 1600 1100 890 760 670 610 560 530
ELEVATION (FEET ABOVE SEA LEVEL)
0-1,999 2,000-4,999 5,000-5,999 6,000-7,999 8,000-10,000
NATURAL GAS
ORIFICE SIZE 45 45 45 45
See
Table 11
MAN. PRESSURE
3.5 3.5 3.5 ‡ 3.2 ‡ 2.8 ‡
(IN W.C.)
LP/PROPANE GAS
ORIFICE SIZE 55 55 56 56
See
Table 11
MAN. PRESSURE
10.0 8.5 10.0 9.0 8.5
(IN W.C.)
‡ = Based on heating value from 900 to 999 BTUH. For heating values less than 900 BTUH multiply
manifold pressure by 1.1 for corrected pressure. For heating values greater than 1,000 BTUH,
multiply manifold pressure by 0.9 for corrected pressure.
Furnace Rating Orifi ce Drill Size Furnace Rating Orifi ce Drill Size
Plate Input (Btu/h) Nat. LP Plate Input (Btu/h) Nat. LP
40,000 45 55 40,000 45 56
60,000 45 55 60,000 45 56
80,000 45 55 80,000 45 56
100,000 45 55 100,000 45 56
120,000 45 55 120,000 46 56