NOTE: A 2-in. diameter pipe must be used within the furnace
casing. Make all pipe diameter transitions outside furnace casing.
f. Install casing hole filler cap (factory-supplied in loose parts
bag) in unused combustion-air pipe casing hole.
g. Drill a 1/8-in. hole in 2-in. combustion-air pipe using hole
in intake housing as a guide.
h. Install a field-supplied No. 6 or No. 8 sheet metal screw
into combustion-air pipe.
NOTE: DO NOT OVERTIGHTEN SCREW. Breakage of intake
housing or fitting may cause air leakage to occur.
NOTE: Do not attach combustion-air intake pipe permanently to
combustion-air intake housing since it may be necessary to remove
pipe for service of igniter or flame sensor.
COMBUSTION-AIR INTAKE HOUSING PLUG FITTING
The combustion-air intake plug fitting must be installed in
unused combustion-air intake housing. This fitting must be
attached by using RTV sealant, or by drilling a 1/8-in. hole in
fitting, using hole in intake housing as a guide. Install a
field-supplied No. 6 or No. 8 sheet metal screw.
NOTE: DO NOT OVERTIGHTEN SCREW. Breakage of intake
housing or fitting may cause air leakage to occur.
A plugged drain connection has been provided on this fitting
for use when moisture is found in combustion-air intake pipe
and combustion box.
NOTE: Moisture in combustion-air intake may be result of
improper termination. Ensure combustion-air intake pipe termina-
tion is similar to that shown in Fig. 37, 38, 39, 40, or 41 so it will
not be susceptible to areas where light snow or other sources of
moisture could be pulled in.
If use of this drain connection is desired, drill out fitting’s tap
plug with a 3/16-in. drill and connect a field-supplied 3/8-in.
tube. This tube should be routed to open condensate drain for
furnace and A/C (if used), and should be trapped. (See Fig.
36.)
2. Attach vent pipe as follows:
a. Determine location of vent pipe connection to inducer
housing as shown in Fig. 34 for application.
b. Reposition elastomeric (rubber) inducer housing outlet cap
and clamp to appropriate unused inducer housing connec-
tion. Tighten clamp.
Inducer housing outlet cap must be installed and fully seated
against inducer housing. Clamp must be tightened to prevent
any condensate leakage. Failure to follow this warning could
result in electrical shock, fire, personal injury, or death.
c. Install pipe support (factory-supplied in loose parts bag)
into selected furnace casing vent pipe hole. Pipe support
should be positioned to bottom of casing hole.
Vent pipe must be installed and fully seated against inducer
housing internal stop. Clamp must be tightened to prevent any
condensate leakage. Failure to follow this warning could
result in electrical shock, fire, personal injury, or death.
NOTE: A 2-in. diameter pipe must be used within the furnace
casing. Make all pipe diameter transitions outside furnace casing.
d. Be certain that mating surfaces of inducer housing connec-
tion, elastomeric coupling, and 2-in. diameter vent pipe are
clean and dry. Assemble the elastomeric (rubber) vent
coupling (with 2 loose clamps) onto inducer housing
connection. Insert the 2-in. diameter vent pipe through the
elastomeric (rubber) coupling and fully into inducer hous-
ing connection until it bottoms on the internal stop. Tighten
both clamps to secure the pipe to inducer housing. Tighten
the clamp screws to 15 in.-lb. of torque.
e. Install casing hole filler cap (factory-supplied in loose parts
bag) in unused combustion-air pipe casing hole.
3. Working from furnace to outside, cut pipe to required
length(s).
4. Deburr inside and outside of pipe.
5. Chamfer outside edge of pipe for better distribution of primer
and cement.
6. Clean and dry all surfaces to be joined.
Fig. 33—Combustion-Air and Vent Pipe Diameter
Transition Location and Elbow Configuration
A93034
FURNACE
PIPE DIAMETER
TRANSITION IN
VERTICAL SECTION
NOT IN
HORIZONTAL
SECTION
Fig. 34—Combustion-Air and Vent Pipe
Connections
A96187
COMBUSTION-
AIR
COMBUSTION-
AIR
AIR
FLOW
VENT
VENT
VENT
AIR
FLOW
AIR
FLOW
AIR
FLOW
UPFLOW DOWNFLOW
HORIZONTAL-LEFT DISCHARGE HORIZONTAL-RIGHT DISCHARGE
Select 1 vent pipe connection and
1 combustion-air pipe connection.
COMBUSTION-
AIR
COMBUSTION-
AIR
COMBUSTION-
AIR
COMBUSTION-
AIR
VENT
VENT
VENT
NOTE: Select 1 vent pipe connection and
1 combustion-air pipe connection.
NOTE:
27
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