Table 5—Maximum Capacity of Pipe *
NOMINAL
IRON PIPE
SIZE (IN.)
INTERNAL
DIAMETER (IN.)
LENGTH OF PIPE (FT)
10
20
30
40
50
1/2
0.622
175
120
97
82
73
3/4
0.824
360
250
200
170
151
1
1.049
680
465
375
320
285
1-1/4
1.380
1400
950
770
660
580
1-1/2
1.610
2100
1460
1180
990
900
Ref: Table 10-2 NFPA 54/ANSI Z223.1-1992.
* Cubic ft of gas per hr for gas pressures of 0.5 psig (14-in. wc) or less, and a pressure drop of 0.5-in. wc (based on a 0.60 specific gravity gas).
CAUTION: If a flexible connector is required or allowed by the authority having jurisdiction, black iron pipe shall be
installed at the gas valve and extend a minimum of 2 in. outside the furnace casing.
WARNING: Use the proper length of pipes to avoid stress on the gas control manifold. Failure to follow this warning
could result in a gas leak, causing fire, explosion, personal injury, or death.
CAUTION: Connect the gas pipe to the furnace using a backup wrench to avoid damaging gas controls.
WARNING: Never purge a line into a combustion chamber. Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water solution to check for gas leaks. Failure to follow this warning could
result in fire, explosion, personal injury, or death.
Joint compounds (pipe dope) should be applied sparingly and only to the male threads of the joints. This pipe dope must be resistant to the action
of propane gas.
Install an accessible manual shut-off valve upstream of the furnace gas controls and within 72 in. of the furnace. A 1/8-in. NPT plugged tapping,
accessible for test gage connection, must be installed immediately upstream of the gas supply connection to the furnace and downstream of the
manual shut-off valve. Place a ground joint union between the gas control manifold and the manual shut-off.
Install a sediment trap in the riser leading to the furnace. The trap can be installed by connecting a tee to the riser leading from the furnace. Connect
a capped nipple into the lower end of the tee. The capped nipple should extend below the level of the gas controls. (See Fig. 10.)
Piping should be pressure tested in accordance with local and national plumbing and gas codes before the furnace has been attached. If the pressure
exceeds 0.5 psig (14-in. wc), the gas supply pipe must be disconnected from the furnace and capped before the pressure test. If the test pressure
is equal to or less than 0.5 psig (14-in. wc), close the manual shut-off valve located on the gas valve before the test. It is recommended that the
ground joint union be loosened before pressure testing.
After all connections have been made, purge the lines and check for gas leakage with regulated gas supply pressure.
Fig. 10—Typical Gas Pipe Arrangement
A89414
GAS
SUPPLY
MANUAL
SHUTOFF
VALVE
SEDIMENT
TRAP
UNION
—10—
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