11
When the gas piping enters through the right side of the
furnace, the installer must supply the following fitings (start-
ing at the gas valve):
•
90 degree elbow.
•
Close nipple.
•
90 degree elbow.
•
Straight pipe to reach exterior of furnace (Figure 15).
A ground joint union, drip leg, and manual shutoff valve
must also be supplied by the installer. In some cases, the
installer may also need to supply a transition piece from
1/2” to another pipe size.
Figure 15
Gas Inlet Through Right Side (Counterflow)
“Left side” and “right side” above are as viewed for a
counterflow installation. Adaptation for horizontal airflow
should be self explanatory.
Gas Piping Checks
Before placing in operation, leak test the unit and gas
connections.
WARNING
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.
CAUTION
To prevent personal injury or property
damage due to fire, the following
instructions must be performed regarding
gas connections, pressure testing, location
of shutoff valve, and installation of gas
piping.
NOTE:
Never exceed specified pressures for testing.
Higher pressure may damage the gas valve and cause
subsequent overfiring, resulting in heat exchanger failure.
To avoid the possibility of explosion or fire, never use a
match or open flame to test for leaks.
This unit and shutoff valve must be disconnected from the
gas supply piping system before supply piping system
pressure testing with test pressures in excess of 1/2 psig
(3.48 kPa).
This unit must be isolated from the gas supply system by
closing its manual shutoff valve before pressure testing of
gas supply piping system with test pressures equal to or
less than 1/2 psig (3.48 kPa).
Propane Gas Tanks and Piping
WARNING
Propane gas is heavier than air and any
leaking gas can settle in any low areas or
confined spaces. To prevent death,
personal injury, or property damage due to
fire or explosion caused by a propane gas
leak, install a gas detection warning device.
A gas detecting warning device is the only reliable way to
detect a propane gas leak. Rust can reduce the level of
odorant in propane gas. Contact a local propane gas
supplier about installing a gas detecting warning device. If
the presence of gas is suspected follow the warning instruc-
tions on page 2 of this manual.
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
10 inch WC at the furnace manifold with all gas appliances
in operation. Maintaining proper gas pressure depends on
three main factors:
1. Vaporization rate, depending on temperature of the
liquid, and “wetted surface” area of the container or
containers.
2. Proper pressure regulation. Two-stage regulation is
recommended for both cost and efficiency.
3. Pressure drop in lines between regulators, and be-
tween second stage regulator and the appliance. Pipe
size will depend on length of pipe run and total load of
all appliances.
Complete information regarding tank sizing for vaporiza-
tion, recommended regulator settings, and pipe sizing is
available from most regulator manufacturers and propane
gas suppliers.
Since propane gas will quickly dissolve white lead or most
standard commercial compounds, special pipe dope must
be used. Shellac base compounds resistant to the actions
of liquefied petroleum gases such as Gasolac
®
, Stalactic
®
,
Clyde’s
®
or John Crane
®
are satisfactory.
