TaNe 9--Maximum Allowable Exposed Vent Pipe Length {ft) With and Without Insulation in Winter Design
Temperature Ambient*
WINTER DESIGN MAX PBPE
FURNACE WITHOUT W_TH 3t8=lN. OR
TEMPERATURE DIAMETER
SRZE (°F) (BN.} INSULATION THICKER INSULATIONt
20 1.5 51 70
0 1.5 28 70
-20 1.5 16 70
040
20 2 45 70
0 2 22 70
-20 2 10 58
20 2 65 70
060 0 2 35 70
-20 2 20 70
20 2 55 55
0 2 48 55
-20 2 30 55
080
20 2.5 70 70
0 2.5 47 70
-20 2.5 28 70
20 2.5 40 40
0 2.5 40 40
-20 2.5 38 40
100
20 3 70 70
0 3 50 70
-20 3 28 70
20 3 70 70
0 3 61 70
-20 3 37 70
120
20 4 70 70
0 4 48 70
-20 4 23 70
* Pipe length (fi) specified for maximum pipe lengths located Jn unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe length
as specified in Table 9.
? Insulation thickness based on R value of 35 per in.
FIELD
LOCATION
=FACTORY
INSTALLED
LOCATION
I
A00212
Fig. 31--Relocating &Box
c Install pipe support (_ilctow-supplied in loose parts bag)
into selected fimaace 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.
29
e. Make sure elbow is oriented in an acceptable direction and
that the minimum clearance of 3 in is observed. (See Fig.
34.)
L 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
h Install casing hole filler cap (factow-supplied) in loose
parts bag) in unused combustion-air pipe casing hole
NOTE: Do not attach combustion-air intake pipe permanently to
combustion-air intake honsing since it may be necessaw to remove
pipe for service of igniter or flame sensor.
(OMBUSTION=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 1i%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 OVERTIGHT]EN SCREW. Breakage of intake
housing or fitting may cause air leakage to occur.
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