Bryant 345MAV - Manual (Page 23)

1. Assemble combustion-air inlet pipe.
a. Permanently install perforated disk assembly (factory-
supplied in loose parts bag) in combustion-air elbow
using RTV or by cementing. (See Fig. 29.)
For 120,000 Btuh size units only: Separate the 2 halves
of perforated disk assembly and use only the shouldered
disk half.
b. Determine length of straight portion of combustion-air
inlet pipe from table in Fig. 29.
c. Cut field-supplied 2-in diameter PVC pipe to determined
length.
d. Permanently attach elbow/perforated disk assembly to
straight portion of pipe using RTV or by cementing. (See
Fig. 29.)
2. Attach combustion-air inlet pipe.
a. Determine location of combustion-air intake pipe con-
nection to combustion-air intake housing as shown in
Fig. 28 for application.
b. Reposition combustion-air intake housing plug fitting in
appropriate unused intake housing connection.
c. Install pipe support (factory-supplied in loose parts bag)
into selected furnace casing combustion-air pipe hole.
Pipe support should be positioned at bottom of casing
hole.
d. Insert assembled combustion-air inlet pipe into intake
housing.
e. Make sure elbow is oriented in an acceptable direction
and that the minimum clearance of 3 in. is observed. (See
Fig. 28.)
f. Drill a 1/8-in. hole in 2-in. combustion-air inlet pipe
using hole in intake housing as a guide.
g. Install a field-supplied No. 6 or No. 8 sheet metal screw
into combustion-air pipe.
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 ignitor 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 to 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. 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. 30.)
C. Vent Pipe
NOTE: Furnace vent pipe connections are sized for 2-in. pipe.
Any vent pipe size change should be made outside furnace casing
in vertical pipe. (See Fig. 31.) This allows proper drainage of vent
condensate.
Determine vent pipe diameter and maximum pipe lengths using
Table 4.
Furnace vent pipe connection must be attached as shown in Fig.
28. Inducer housing alternate vent cap may need to be relocated in
some applications.
NOTE: Starting at furnace, slope vent pipe a minimum of 1/4 in.
per linear ft upward to termination(s) with no sags between
hangers.
Fig. 29—Combustion-Air Inlet Pipe Assembly
LENGTH OF STRAIGHT PIPE PORTION OF
COMBUSTION-AIR INLET PIPE ASSEMBLY (IN.)
CASING WIDTH A
17-1/2 8-1/2 ± 1/2
21 10-1/2
±
1/2
24-1/2 12 ± 1/2
A96211
FIELD-SUPPLIED
2-IN. DIAMETER
PVC PIPE
FIELD-SUPPLIED
2-IN. DIAMETER
PVC 90
°
ELBOW
COMBUSTION-AIR DISC
(FACTORY-SUPPLIED IN
LOOSE PARTS BAG)
A
Fig. 30—Intake Housing Plug Fitting Drain
A96190
COMBUSTION–
AIR PIPE
BURNER
BOX
COMBUSTION–AIR
INTAKE HOUSING
3/8
″
ID TUBE
TRAP
TO OPEN
DRAIN
3/16
″
DRILL
HOUSING
PLUG
4
″
MIN
Fig. 31—Vent Pipe Diameter Transition Location and
Elbow Configuration
A93034
FURNACE
PIPE DIAMETER
TRANSITION IN
VERTICAL SECTION
NOT IN
HORIZONTAL
SECTION
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