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Table 25 - Propane (kBtu/hr) Maximum Piping Capacities
Specific Gravity = 1.52, Supply Pressure = 11" w.c., Pressure Drop, 0.5" w.c.
Pipe Size
1-1/4"
1-1/2"
2"
2-1/2"
3"
12510
4"
25520
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 Example
A 100 ft pipe run is needed for a 1710 MBH
natural gas heater. The natural gas has a
rating of 1000 BTU/ft
of 0.6 (Obtain these values from the local gas
supplier.)
From the natural gas maximum capacities
table, at 100 ft and 1710 ft
minimum pipe size is 2-1/2".
A 100 ft pipe run is needed for a 800 MBH
propane gas heater.
800 MBH = 800 kBtu/hr
From the propane gas maximum capacities
table, at 100 ft and 800 kBtu/hr the required
minimum pipe size is 1-1/2".
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
pressure to the unit is 11" w.c. and the
86
20 ft
50 ft.
1495
910
2295
1415
4330
2645
7045
4340
7705
15730
3
and a specific gravity
3
1710 ft
/hr
3
/hr the required
inlet
gas
Length of Pipe
100 ft.
150 ft.
630
975
1810
1495
2990
2410
5305
4280
10830
8735
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 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 3.5" w.c. for natural gas,
or 10.5" w.c. for propane.
Heater must be disconnected from the
gas supply piping during pressure
testing of the supply piping system with
pressures in excess of ½ psi. Gas
valves can be damaged if subjected to
more than ½ psi.
Gas Pressure Regulator & Overpressure
Protection Device
A gas pressure regulator shall be installed if
natural gas supply pressure to the unit is
greater than 10.5" w.c. and less than 2 psi
(55.4" w.c.) and if propane gas supply
pressure is greater than 13" w.c. and less than
2 psi (55.4" w.c.). Regulators shall comply
with the latest edition of the Standard for Line
Pressure Regulators, ANSI Z21.80/CSA
6.22.
200 ft.
510
435
785
665
1280
2080
3615
7380
CAUTION
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