IM 1287-6 • REBEL APPLIED ROOFTOP 144 www.DaikinApplied.com
Gas Piping Requirements
Gas Pressure Requirements
Inlet gas pressure must be maintained at 7.0” wc for Natural
Gas and 11.0” wc for Propane. Maximum inlet pressure must
not exceed 13.0” wc to prevent damage to the gas valve.
Gas piping must be sized and routed to provide the minimum
required pressure when the burner is operating at maximum
input. Consult your local utility on any questions on gas
pressure available, allowable pipe pressure drops, and local
piping requirements. Table 32, Table 33, and Table 34 provided
for sizing reference.
Install all piping in accordance with the National Fuel Gas
Code (ANSI Z223.1), (NFPA 54-1999) and any applicable local
codes.
Remove all burrs and obstructions from pipe. A drip leg must
be installed in the vertical line before each burner such that it
will not freeze. All pipe threads must have a pipe dope which is
resistant to the action of LP gas.
After installation, pressurize the piping as required and test
all joints for tightness with a rich soap solution or UL 913
combustible gas leak detector. Any bubbling is considered a
leak and must be eliminated.
Table 32: Natural Gas Pipe Flow Capacity* (CFH)
Gas Capacity in CFH
Pipe Size-inches (Ips)
Pipe Length
(ft)
½ ¾ 1 1¼ 1½ 2 2½ 3 4
10 132 278 520 1050 1600 2050 4800 8500 17500
20 92 190 350 730 1100 2100 3300 5900 12000
30 73 152 285 590 890 1650 2700 4700 9700
40 63 130 245 500 760 1450 2300 4100 8300
50 56 115 215 440 670 1270 2000 3600 7400
60 50 105 195 400 610 1150 1850 3250 6800
70 46 96 180 370 560 1050 1700 3000 6200
80 53 90 170 350 530 990 1600 2800 5800
90 40 84 160 320 490 930 1500 2600 5400
100 38 79 150 305 460 870 1400 2500 5100
125 34 72 130 275 410 780 1250 2200 4500
150 31 64 120 250 380 710 1130 2000 4100
175 28 59 110 225 350 650 1050 1850 3800
200 26 55 100 210 320 610 980 1700 3500
*Assuming Pressure Drop of 0.3" Wc & Specic Gravity of 0.60
Table 33: Conversion for Specic Gravities other than 0.60
Natural Gas Multiplier
0.50 1.100
0.60 1.000
0.70 0.936
0.80 0.867
0.90 0.816
1.00 0.775
Propane-Air Multiplier
1.10 0.740
Propane Multiplier
1.55 0.622
Butane Multiplier
2.00 0.547
Table 34: Conversion for Pressure Drop other than 0.3”
Inches W.C.
Pressure Drop
Multiplier
Inches W.C.
Pressure Drop
Multiplier
0.1 0.577 1.0 1.83
0.2 0.815 2.0 2.58
0.3 1.000 3.0 3.16
0.4 1.16 4.0 3.65
0.6 1.42 6.0 4.47
0.8 1.64 8.0 5.15
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