AAON RN Series, Installation Operation & Maintenance, Page: 99 / 136

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Table 34 - Natural Gas (ft 3 /hr) Maximum Piping Capacities
Specific Gravity = 0.6, Supply Pressure ≤ 0.5 psi, Pressure Drop = 0.5” w.c.
Pipe Size
Length of Pipe
20 ft 50 ft. 100 ft. 150 ft. 200 ft.
1/2”
120 73 50 40 35
3/4”
250 151 103 84 72
1”
465 285 195 160 135
1-1/4” 950 580 400 325 280
1-1/2” 1460 900 620 500 430
2”
2750 1680 1150 950 800
2-1/2” 4350 2650 1850 1500 1280
Table 35 - Propane (kBtu/hr) Maximum Piping Capacities
Specific Gravity = 1.52, Supply Pressure = 11” w.c., Pressure Drop, 0.5” w.c.
Pipe Size
Length of Pipe
20 ft 50 ft. 100 ft. 150 ft. 200 ft.
1/2”
189 114 78 63 55
3/4”
393 237 162 132 112
1”
732 448 307 252 213
1-1/4” 1496 913 630 511 440
1-1/2” 2299 1417 976 787 675
2”
4331 2646 1811 1496 1260
Do not use gas piping smaller than unit gas
connections. Natural gas pipe runs longer
than 20 feet and propane gas pipe runs longer
than 50 feet may require a larger supply pipe
than the unit connection size. Some utility
companies may also require pipe sizes larger
than the minimum sizes listed.
Piping Sizing Examples
A 100 ft pipe run is needed for a 1080 MBH
natural gas heater. The natural gas has a
rating of 1000 Btu/ft
3
and a specific gravity
of 0.6 (Obtain these values from the local gas
supplier.)
 
BTU
ft
MBH
1000
1080
3
1080 ft
3
/hr
From the natural gas maximum capacities
table, at 100 ft and 1080 ft
3 /hr the required
minimum pipe size is 2”.
A 100 ft pipe run is needed for a 270 MBH
propane gas heater.
270
MBH = 270 kBtu/hr
From the propane gas maximum capacities
table, at 100 ft and 270 kBtu/hr the required
minimum pipe size is 1”.
Inlet and Manifold Pressures
For natural gas units, the minimum inlet gas
pressure to the unit is 6” w.c. and maximum
inlet gas pressure to the unit is 10.5” w.c. For
propane units, the minimum
inlet gas
pressure to the unit is 11” w.c. and the
maximum inlet gas pressure to the unit is 13”
w.c. A field provided 1/8” NPT pressure tap
is required to be installed in the piping jus t
upstream of the shutoff valve for test gage
connection to allow checking of the gas
supply pressure at the unit.