Piping Sizing Examples; Inlet And Manifold Pressures; Table 31 - (Metric) Propane (Kw) Maximum Piping Capacities; Table 32 - (Imperial)Propane (Kbtu/Hr) Maximum Piping Capacities - AAON RQ NextGen Series Installation Operation & Maintenance

Table 31 – (Metric) Propane (kW) Maximum Piping Capacities
Specific Gravity = 1.52, Supply Pressure = 2.34 kpa., Pressure Drop, 0.93 mmHg
Pipe Size
(mm)
12.7
19
25.4
31.75
38.10
50.80 1269.0
Table 32 – (Imperial)Propane (kBtu/hr) Maximum Piping Capacities
- Specific Gravity = 1.52, Supply Pressure = 11" w.c., Pressure Drop, 0.5" w.c.
Pipe Size
1/2"
3/4"
1"
1-1/4"
1-1/2"
2"
Do not use gas piping smaller than unit gas
connections. Natural gas pipe runs longer
than 6.1 meters (20 feet) and propane gas
pipe that runs longer than 15.2 meters (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
3
rating of 1000 Btu/ft
of 0.6 (Obtain these values from the local gas
supplier.)
ft 3
1080
MBH ×
1000 Btu
From the natural gas maximum capacities
table, at 100 ft and 1080 ft
minimum pipe size is 2".
A 100 ft pipe run is needed for a 270 MBH
propane gas heater.
6.1 m 15.2 m
0.6 0.4
1.3 0.8
2.5 1.5
438.1 266.7
672.6 414.7
775.2
20 ft 50 ft.
189 114
393 237
732 448
1496 913
2299 1417
4331 2646
and a specific gravity
3
1080 ft /hr
=
3
/hr the required
Length of Pipe
30.4 m 45.6 m
0.3
0.6
1.0
184.6 149.5
285.7 230.1
530.5 438.1
Length of Pipe
100 ft. 150 ft.
78
162
307
630
976
1811 1496
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 11.2 mmHg (6" w.c.)
and maximum inlet gas pressure to the unit is
19.6 mmHg (10.5" w.c.) For propane units,
the minimum inlet gas pressure to the unit is
20.6 mmHg (11" w.c.) and the maximum
inlet gas pressure to the unit is 24.3 mmHg
(13" w.c.) A field provided 0.3 cm (1/8")
NPT pressure tap is required to be installed in
the piping just upstream of the shutoff valve
for test gage connection to allow checking of
the gas supply pressure at the unit.
A factory installed pressure tap on the outlet
end of the gas valve can be used to verify a
manifold pressure of 6.5 mmHg (3.5" w.c.)
60.8 m
0.2 0.2
0.5 0.4
0.9 0.7
127.5
194.9
375.1
200 ft.
63 55
132 112
252 213
511 440
787 675
1260
83