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used on the condensate drip leg and line. Heating
cable kit is available from Lennox in various lengths;
6feet (1.8m) - kit no. 18K48; 24 feet (7.3m) - kit no.
18K49; and 50 feet (15.2m) - kit no. 18K50.
Gas Piping
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.
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
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 5 lists recommended pipe sizes for typical ap-
plications.
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 waiters
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
piping will clear combustion air inducer. See figure 23.
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 suitable
hangers or straps. A drip leg should be installed in verĆ
tical pipe runs to the unit.
5 - In some localities, codes may require installation of a
manual main shut-off valve and union (furnished by inĆ
staller) external to the unit. Union must be of the
ground joint type.
IMPORTANT
Compounds used on threaded joints of gas piping
must be resistant to the actions of liquified petroĆ
leum gases.
FIGURE 24
MANUAL MAIN SHUT-OFF
VALVE WILL NOT HOLD
NORMAL TEST PRESSURE
CAP
FURNACE
ISOLATE
GAS VALVE
1/8 IN. (3.2mm) N.P.T.
PLUGGED TAP
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.
Leak Check
After gas piping has been completed, carefully check all
piping connections (factory and field) for gas leaks. Use a
leak detecting solution or other preferred means.
CAUTION
Some soaps used for leak detection are corrosive to
certain metals. Carefully rinse piping thoroughly afĆ
ter leak test has been completed. Do not use
matches, candles, flame or other sources of ignition
to check for gas leaks.
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