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APPENDIX C – GAS PIPING
ASSURE GAS PIPING IS LEAK FREE
AND OF PROPER SIZE and type for the
connected load.
SHUT OFF MAIN GAS SUPPLY prior to
installing or servicing boiler gas piping.
1. Determine the boiler’s maximum gas
demand and minimum gas supply pressure
(printed on the boiler’s rating label) and the
demand of other gas appliances served by
the same gas meter.
2. Ensure that gas piping, ttings, and gas
meter capacities can supply the maximum
gas demand of all appliances at pressures
above their minimum allowable gas
pressure. Tables C-1 and C-2 provide typical
capacities of gas pipes and ttings.
3. Derate the gas ow through pipes by
multiplying by a correction factor in Table
C-3 based on the specic gravity of the gas.
4. For materials or conditions other than those
listed above, refer to the National Fuel Gas
Table C-1: Maximum Capacity of Schedule 40 Pipe in Cubic Feet Per Hour (CFH)
*
Length
(Feet)
0.3” w.c. Pressure Drop 0.5” w.c. Pressure Drop
½ ¾ 1 1¼ ½ ¾ 1 1¼
10 132 278 520 1050 175 360 680 1400
20 92 190 350 730 120 250 465 950
30 73 152 285 590 97 200 375 770
40 63 130 245 500 82 170 320 660
50 56 115 215 440 73 151 285 580
60 50 105 195 400 66 138 260 530
70 46 96 180 370 61 125 240 490
80 43 90 170 350 57 118 220 460
90 40 84 160 320 53 110 205 430
100 38 79 150 305 50 103 195 400
*1 CFH of Natural Gas is approximately equal to 1000 BTU/hr; 1 CFH of LP is approximately equal to 2500 BTU/hr.
Table C-2: Equivalent Lengths (ft) Of Standard Pipe Fittings & Valves
Pipe
Size
Gate Globe Angle
Swing
Check
90°
Elbow
45°
Elbow
90° ‘T’, Flow
Through Run
90° ‘T’, Flow
Through Branch
½” 0 19 9 4 2 1 1 3
¾” 0 23 12 5 2 1 1 4
1” 1 29 15 7 3 1 2 5
1 ¼” 1 39 20 9 4 2 2 7
1 ½” 1 45 22 11 5 3 3 8
Code, NFPA54/ANSI Z223.1, or size the
system using standard engineering methods
acceptable to authority having jurisdiction.
USE PROPER THREAD COMPONENTS
on all gas connectors.
USE THREAD (JOINT) COMPOUNDS
(pipe dope) rated for liqueed petroleum
gas.
Table C-3: Specic Gravity Correction Factors For
Natural Gas
Specic
Gravity
Correction
Factor
Specic
Gravity
Correction
Factor
0.50 1.10 0.85 0.81
0.55 1.04 0.90 0.82
0.60 1.00 1.00 0.78
0.65 0.96 1.10 0.74
0.70 0.93 1.20 0.71
0.75 0.90 1.30 0.68
0.80 0.87 1.40 0.66