EXAMPLE:
An 080-12 size furnace located in Indianapoli< elevation
650 ft above sea level, could be installed in an application
requiring 3 elbows and 32 ft of vent pipe, along with 5
elbows and 34 ft of combustion-air pipe. Table 7 indicates
this application would allow a 2-in. diameter vent pipe, but
require a 2-1/2 im diameter combustion air pipe (2-ira pipe
is good for 35 fi with 3 elbows, but only 30 ft with 5
elbows) Therefore, 2-i/2 in. diameter pipe must be used
for both vent and combustion-air pipes since larger required
diameter must always be used for both pipes. If same
installation were in Albuquerque, elevation 5250 ft above
sea level, installation would require 2-1/2 in. vent pipe and
combustion-air pipe. At 5001- to 6000-ft elevation, 2-in.
pipe is only good fbr 17 ff with 5 elbows, and 2-1/2 in. pipe
is good fbr 70 ft with 5 elbows.
Corubustion-Air and Vent Pipe Attachment
NOTE: All pipe joints must be cemented except attachment of
combustion-air pipe to inlet housing connectiom since it may be
necessary to remove pipe for servicing.
1. Attach combustion-air pipe as fbllows:
a. Detem_ine location of combustion-air intake pipe connec-
tion to combustion-air intake housing as shown in Fig. 33
fbr application.
b. Reposition combustion-air intake housing plug fitting in
appropriate unused intake housing connection.
c. If required per Table 7, insert perforated disk assembly
(factory-supplied in loose parts bag) in intake housing
where combustion-air intake pipe will be connected If half
disk set is required, install with shoulder of disk against
stop in combustion-air inlet,
d, Install pipe support (I:i_ctow-supplied in loose parts bag)
into selected _ilrnace casing combustion-air pipe hole, Pipe
support should be positioned at bottom of casing hole
e. Insert 2-ira diameter pipe into intake housing.
NOTE: A 2-in. diameter pipe must be used within the Nrnace
casing. Make all pipe diameter transitions outside fi/rnace casing.
f Install casing hole filler cap (factory-supplied in loose parts
bag) in unused combustion-air pipe casing hole.
g. Drill a 1i8-im hole in 2-ira 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 OVER TIGHTEN SCREW. Breakage of intake
housing or fitting may cause air leakage m 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 &illing a 1i8-im 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 OVER TIGHTEN' SCREW. Breakage of intake
housing or fitting may cause air leakage to occur.
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A plugged &ain connection has been provided on this fitting
_br use when moisture is _bnnd in combustion-air intake pipe
and combustion box.
NOTE: Moisture in conft_ustion-air intake may be result of
improper terminatiom Ensure combustion-air intake pipe tem_ina-
tion is similar to that shown in Fig. 36, 37, 38, 39, and 40 so it will
not be susceptible to areas where light snow or other sources of
moisture could be pulled in.
If use of this &ain connection is desired, drill out fitting's tap
plug with a 3/16-in. &ill and connect a field-supplied 3/8-im
tube. This tube should be routed to open condensate drain fbr
fhmace and AiC (if used), and should be trapped. (See Fig.
35.)
2. Attach vent pipe as _bllows:
a. Detem?ine location of vent pipe connection to inducer
housing as shown in Fig. 33 for application.
b. Reposition etastomeric (rubber) inducer housing outlet cap
and clamp to appropriate unused inducer housing connec-
tion. Tighten clamp.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in unit component
damage.
Inducer housing outlet cap must be installed and t:iflly seated
against inducer housing. (lamp must be tightened to prevent
any condensate leakage
c Install pipe support (fi_ctory-supplied in loose parts bag)
into selected f_lrnace casing vent pipe hole. Pipe support
should be positioned at bottom of casing hole.
UNIT DAMAGE HAZARD
Failure to follow this caution may result in unit component
damage.
Vent pipe must be installed and fully seated against inducer
housing internal stop. Clamp must be tightened to prevent any
condensate leakage
NOTE: A 2-ira diameter pipe must be used within the furnace
casing Make all pipe diameter transitions outside furnace casing.
d. Be certain that mating surftces of inducer housing connec-
tion, elastomeric (rubber) 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 (rnbber) coupling and fiflly 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 (factow-supplied in loose parts
bag) in unused vent pipe casing hole.
Vent Extension Pipe
Furnaces with i00,000 Btuh and larger inputs are supplied
with a PVC vent extension pipe (2-ira diameter by 12-in.
long). This pipe has a built-in channel to assist vent conden-
sate disposal. When this vent extension pipe is supplied, it
must be used to connect the field vent pipe to/_urnace inducer
housing on ALL upflow and downflow applications.
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