32
TABLE 9
NATURAL GAS PIPE CAPACITY TABLE (CU. FT./HR.)
Capacity of gas pipe of different diameters and lengths in cu. ft. per hr. with pressure drop of 0.3 in. and
specific gravity of 0.60 (natural gas).
Nominal Length of Pipe, Feet
Iron Pipe
Size, Inches 10 20 30 40 50 60 70 80
1/2 132 92 73 63 56 50 46 43
3/4 278 190 152 130 115 105 96 90
1 520 350 285 245 215 195 180 170
1-1/4 1,050 730 590 500 440 400 370 350
1-1/2 1,600 1,100 890 760 670 610 560 530
After the length of pipe has been determined, select the pipe size which will provide the minimum cubic
feet per hour required for the gas input rating of the furnace. By formula:
Gas Input of Furnace (BTU/HR)
Cu. Ft. Per Hr. Required =
Heating Value of Gas (BTU/FT
3
)
The gas input of the furnace is marked on the furnace rating plate. The heating value of the gas
(BTU/FT3) may be determined by consulting the local natural gas utility or the LP gas supplier.
TABLE 10
LP GAS PIPE CAPACITY TABLE (CU. FT./HR.)
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied petroleum gases (at 11
inches water column inlet pressure).
(Based on a Pressure Drop of 0.5 Inch Water Column)
Nominal Length of Pipe, Feet
Iron Pipe
Size, Inches 10 20 30 40 50 60 70 80 90 100 125 150
1/2 275 189 152 129 114 103 96 89 83 78 69 63
3/4 567 393 315 267 237 217 196 182 173 162 146 132
1 1,071 732 590 504 448 409 378 346 322 307 275 252
1-1/4 2,205 1,496 1,212 1,039 913 834 771 724 677 630 567 511
1-1/2 3,307 2,299 1,858 1,559 1,417 1,275 1,181 1,086 1,023 976 866 787
2 6,221 4,331 3,465 2,992 2,646 2,394 2,205 2,047 1,921 1,811 1,606 1,496
Example (LP): Input BTU requirement of unit, 150,000
Equivalent length of pipe, 60 ft. = 3/4" IPS required.
LP COPPER TUBE SIZING TABLE
Sizing between single or second stage (low pressure) regulator and appliance. Maximum capacity of pipe in thousands of BTU
per hour of undiluted propane gases (at 11" w.c. setting).
Outside Diameter
Length of Pipe, Feet
Copper Tubing,
Type L 10 20 30 40 50 60 80 100 125 150
3/8" 49 34 27 23 20 19 16 14 11 10
1/2" 110 76 61 52 46 42 36 32 28 26
5/8" 206 141 114 97 86 78 67 59 52 48
3/4" 348 239 192 164 146 132 113 100 89 80
7/8" 536 368 296 253 224 203 174 154 137 124
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