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30
Length
(Feet)
0.3 Inch w.c. Pressure Drop 0.5 Inch w.c. Pressure Drop
½ ¾ 1 1¼ ½ ¾ 1 1¼
10 132 278 520 1,050 175 360 680 1,400
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
Table 6: Maximum Capacity of Schedule 40 Pipe in CFH for Gas Pressures of 0.5 psig or Less
Table 7: Equivalent Lengths of Standard Pipe Fittings & Valves
Pipe
Size
I.D.
(Inches)
Valves (Fully Open) Threaded Fittings
Gate Globe Angle
Swing
Check
90°
Elbow
45°
Elbow
90° Tee, Flow
Through Run
90° Tee, Flow
Through Branch
½” 0.622 0.35 18.6 9.3 4.3 1.6 0.78 1.0 3.1
¾” 0.824 0.44 23.1 11.5 5.3 2.1 0.97 1.4 4.1
1” 1.049 0.56 29.4 14.7 6.8 2.6 1.23 1.8 5.3
1¼” 1.380 0.74 38.6 19.3 8.9 3.5 1.6 2.3 6.9
Specic
Gravity
Correction
Factor
Specic
Gravity
Correction
Factor
0.50 1.10 1.30 1.07
0.55 1.04 1.40 1.04
0.60 1.00 1.50 1.00
0.65 0.96 1.60 0.97
0.70 0.93 1.70 0.94
0.75 0.90 --- ---
0.80 0.87 --- ---
Table 8: Specic Gravity Correction Factors
WARNING
Do not use matches, candles, open ames, or
other ignition source.
Figure 24: Recommended Gas Piping
C. Pressure Test. The boiler and its gas connection must
be leak tested before placing boiler in operation.
1. Protect boiler gas valve. For all testing over ½ psig,
boiler and its individual shut-off valve must be
disconnected from gas supply piping. For testing at
½ psig or less, isolate boiler from gas supply piping
by closing boiler’s individual manual shut-off valve.
2. Locate leaks using approved combustible gas
detector, soap and water, or similar nonammable
solution.