Direct/Standard Inlet Piping
Edges of sheet metal holes may be sharp. Use gloves as
a precaution when removing hole plugs.
When gas piping enters directly to the gas control valve through
the standard inlet hole, the installer must supply straight pipe
with a ground joint union to reach the exterior of the furnace. The
rigid pipe must be long enough to reach the outside of the
cabinet to seal the grommet cabinet penetration. A semirigid
connector to the gas piping can be used outside the cabinet per
Indirect/Alternate Inlet Piping
When gas piping enters indirectly to the gas control valve through
the alternate gas inlet hole, the following ¹⁄₂" pipe fittings (starting
from the gas control valve) must be supplied to reach the outside
of the cabinet:
90º street elbow
2¹⁄₂" pipe nipple
NOTE: The straight pipe must be long enough to reach the
outside of the cabinet so as to seal the grommet cabinet
penetration and to install the ground joint union outside of the
cabinet. A semirigid connector to the gas piping can be used
outside the cabinet per local codes.
Gas Piping Checks
Before placing the furnace in operation, leak test the furnace and
To avoid the possibility of explosion or fire, never use a
match or open flame to test for leaks.
Check for leaks using an approved chloride-free soap and water
solution, an electronic combustible gas detector, or other
approved testing methods.
Never exceed specified pressures for testing. Higher pressure
may damage the gas control valve and cause subsequent
overfiring, resulting in heat exchanger failure.
Disconnect this unit and external manual shutoff valve from
the gas supply piping system before pressure testing the
supply piping system with pressures in excess of ¹⁄₂ psig
Isolate this unit from the gas supply piping system by closing
the external manual gas shutoff valve before pressure testing
supply piping system with test pressures equal to or less than
¹⁄₂ psig (3.48 kPa).
Propane Gas Tanks and Piping
If the gas furnace is installed in a basement, and
excavated area or a confined space, it is strongly
recommended to contact a propane supplier to install a
gas detecting warning device in case of a gas leak.
Since propane gas is heavier than air, any leaking can
settle in low areas or confined spaces.
Propane gas odorant may fade, making the gas
undetectable except with a warning device.
A gas detecting warning system is the only reliable way to detect
a propane gas leak. Rust can reduce the level of odorant in
propane gas. Do not rely on your sense of smell. Contact a local
propane gas supplier about installing a gas detecting warning
All propane gas equipment must conform to the safety standards
of the National Board of Fire Underwriters, NBFU Manual 58.
For satisfactory operation, propane gas pressure must be 11"
W.C. at the furnace manifold with all gas appliances in operation.
Maintaining proper gas pressure depends on 3 main factors:
Vaporization rate, depending on temperature of the liquid and
"wetted surface" area of the container or containers.
Proper pressure regulation. Two-stage regulation is
recommended for both cost and efficiency.
Pressure drop in the lines between the regulators, and
stage regulator and the appliance. Pipe size will
depend on the length of the pipe run and the total load of all
Complete information regarding tank sizing for vaporization,
recommended regulator settings, and pipe sizing is available
from most regulator manufacturers and propane gas suppliers.
Since propane gas will quickly dissolve white lead and most
standard commercial compounds, special pipe dope must be
used. Shellac-based compounds resistant to the actions of
liquefied petroleum gases, such as Gasolac
or John Crane
Refer to "Propane Gas Installation—Typical" for typical propane
gas installations and piping.
Propane Gas Installation—Typical
B. 5 to 15 psig (20 psig maximum)
C. 200 psig maximum
E. Continuous 11" W.C.