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Direct/Standard Inlet Piping
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
local codes.
Indirect/Alternate Inlet Piping
When gas piping enters indirectly to the gas control valve through
the alternate gas inlet hole, the following fittings (starting from the
gas control valve) must be supplied to reach the outside of the
cabinet:
Coupling
90º elbow
2" close nipple
90º elbow
Straight pipe with a ground joint union to reach the exterior of
the furnace.
NOTE: The rigid pipe must be long enough to reach the
outside of the cabinet so as to seal the grommet cabinet
penetration. 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
gas connections.
Check for leaks using an approved chloride-free soap and water
solution, an electronic combustible gas detector, or other
approved testing methods.
NOTE: Do not exceed specified pressures for testing. Higher
pressure may damage the gas control valve and cause
subsequent overfiring, resulting in heat exchanger failure. Isolate
this furnace 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
WARNING
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
system.
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 three 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
between 2
nd
stage regulator and the appliance. Pipe size will
depend on the length of the pipe run and the total load of all
appliances.
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 are satisfactory.
Propane Gas Installation—Typical
A
B
st
A. 1
stage regulator
B. 5 to 15 psig (20 psig maximum)
Goodman 64
C
D
nd
C. 2
stage regulator
D. Continuous 11" W.C.
31
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