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Gas Piping
CAUTION
If a flexible gas connector is required or allowed by
the authority that has jurisdiction, black iron pipe
shall be installed at the gas valve and extend outĆ
side the furnace cabinet.
1 - Gas piping may be routed into the unit through either
the left- or right-hand side. Supply piping enters into
the gas valve from the bottom of the valve as shown
in figure 23.
2 - When connecting the gas supply, factors such as
length of run, number of fittings and furnace rating
must be considered to avoid excessive pressure
drop. Table 6 lists recommended pipe sizes for typiĆ
cal applications.
NOTE - Use two wrenches when connecting gas pipĆ
ing to avoid transferring torque to the manifold.
3 - The gas piping must not run in or through air ducts,
clothes chutes, gas vents or chimneys, dumb waitĆ
ers, or elevator shafts. Center gas line through piping
hole. Gas line should not touch side of unit. When
left-hand gas plumbing is required, gas line should
be installed in the lower half of knockout so that pip-
ing will clear combustion air blower. See figure 23.
FIGURE 23
GAS VALVE
LEFT SIDE PIPING
MANUAL MAIN
SHUT-OFF
VALVE
RIGHT SIDE PIPING
(STANDARD)
GAS VALVE
1/8 in. NPT
PLUGGED
TAP
MANUAL MAIN
SHUT-OFF
VALVE
1/8 in. NPT
PLUGGED
TAP
4 –
The piping should be sloped 1/4 inch (6.4 mm) per 15
feet (4.57 m) upward toward the meter from the furĆ
nace. The piping must be supported at proper interĆ
vals [every 8 to 10 feet (2.44 to 3.01 m)] using suitĆ
able hangers or straps. A drip leg should be installed
in vertical pipe runs to the unit.
5 - In some localities, codes may require installation of a
manual main shutĆoff valve and union (furnished by
the installer) external to the unit. Union must be of the
ground joint type.
NOTE - Install a 1/8 inch NPT plugged tap in the field pipĆ
ing upstream of the gas supply connection to the unit. The
tap must be accessible for test gauge connection. See
figure 24.
FIGURE 24
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
CAP
FURNACE
ISOLATE
GAS VALVE
1/8 in. (3.2 mm) NPT
PLUGGED TAP
Leak Check
After gas piping is completed, carefully check all piping
connections (factory- and field-installed) for gas leaks.
Use a leak detecting solution or other preferred means.
IMPORTANT
Some soaps used for leak detection are corrosive
to certain metals. Carefully rinse piping thoroughly
after leak test has been completed. Do not use
matches, candles, flame, or other sources of igniĆ
tion to check for gas leaks.
IMPORTANT
The furnace must be isolated from the gas supply
piping system by closing its individual manual
shut-off valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than 1/2 psig (3.45 kPa). See figure 24.
The furnace and its individual shut-off valve must
be disconnected from the gas supply piping sysĆ
tem during any pressure testing of the system at
test pressures greater than 1/2 psig (3.45 kPa).
