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12. Slope combustion air piping (if applicable) and vent piping
downward towards furnace a minimum of 1/4 in. per linear ft
with no sags between hangers.
13. Horizontal portions of the venting system shall be installed so
as to prevent the accumulation of condensate.
14. Use appropriate methods to seal openings where combustion
air pipe (if applicable) and vent pipe pass through roof or
sidewall.
EXAMPLE:
An 100-14 size furnace located in Indianapolis, elevation
650 ft above sea level, could be installed as either a direct
vent/2-pipe system that requires 3 elbows and 28 ft of vent
pipe, along with 5 elbows and 34 ft of combustion-air pipe
OR a non-direct vent/1-pipe system that requires 3 elbows
and 28 ft vent pipe.
For a direct vent/2-pipe system, Table 11 indicates this
application would allow a 2-in. diameter vent pipe, but
require a 2-1/2 in. diameter combustion air pipe. According
to Table 11, 2-in. diameter pipe is good for 30 ft with 3
elbows, but only 20 ft with 5 elbows. Therefore, 2-1/2 in.
diameter pipe must be used for both vent and combustion-
air pipes since larger required diameter must always be
used for both pipes.
For a non-direct vent/1-pipe system, Table 11 indicates that
this application would allow a 2-in. diameter vent pipe.
If same installations were in Albuquerque, elevation 5250 ft
above sea level:
For a direct vent/2-pipe system, Table 11 indicates that
2-1/2 in. diameter vent pipe and combustion-air pipe are
required.
For a non-direct vent/1-pipe system, Table 11 indicates that
2-1/2-in. diameter vent pipe is required.
If same applications are to be installed at 5001- to 6000 ft
elevation:
For a direct vent/2-pipe system, 2-in. pipe is only good for
23 ft (with 3 elbows) and 13 ft (with 5 elbows). Therefore,
2-1/2 in. diameter combustion air and vent pipe must be
used.
For a non-direct vent/1-pipe system, a 2-in. diameter pipe is
only good for 23 ft with 3 elbows. A 2-1/2-in. diameter vent
pipe must be used.
VENT TERMINATION
General
Combustion-air (direct vent/2-pipe system only) and vent pipe
must terminate outside structure, either through sidewall or roof.
For vent termination clearance, refer to Table 8 for Direct
Vent/2-Pipe system and Table 9 for Non-direct Vent/1-Pipe
system. For exterior piping arrangements, refer to Fig. 43 for
Direct Vent/2-Pipe system and Fig. 44 for Non-Direct/1-Pipe
system.
Roof termination is preferred since it is less susceptible to damage
or contamination, and it has less visible vent vapors. Sidewall
termination require sealing or shielding of building surfaces with a
corrosive resistance material due to corrosive combustion products
of vent system.
NOTE:
(Direct Vent/2-Pipe system ONLY) A factory accessory
termination kit MUST be used. See section
″
Vent Termination Kit
(Direct Vent/2-Pipe System Only)
″
in this instruction.
When determining appropriate location for termination, consider
the following guidelines:
1. Comply with all clearance requirements stated in Table 8 or
Table 9 per application.
2. Termination or termination kit should be positioned where
vent vapors will not damage plants/shrubs or air conditioning
equipment.
3. Termination or termination kit should be positioned so that it
will not be affected by wind eddy, such as inside building
corners, nor by recirculation of flue gases, airborne leaves, or
light snow.
4. Termination or termination kit should be positioned where it
will not be damaged by or subjected to foreign objects such as
stones, balls, etc.
5. Termination or termination kit should be positioned where
vent vapors are not objectionable.
Extended Exposed Sidewall Pipes
Sidewall combustion air pipe termination (direct vent/2-pipe
system only) and vent pipe termination may be extended beyond
area shown in Fig. 43 or in Fig. 44 per application in outside
ambient by insulating pipe as indicated in Table 10.
1. Determine combustion air pipe diameter (direct vent/2-pipe
system only) and vent pipe diameter, as stated above, using
total pipe length and number of elbows.
2. Using winter design temperature (used in load calculations),
find appropriate temperature for your application and furnace
model.
3. Determine required insulation thickness for exposed pipe
length(s).
NOTE:
Pipe length(ft) specified for maximum pipe lengths lo-
cated in unconditioned spaces cannot exceed total allowable pipe
length as specified in Table 8.
Vent Termination Kit (Direct Vent/2-Pipe System Only)
NOTE:
Always refer to the instructions in termination kit for the
latest version.
Combustion air and vent pipes MUST terminate outside structure.
A factory accessory termination kit must be installed as shown in
Table 12. There are four options of vent/combustion air termina-
tion kits available as shown in Table 12.
NOTE:
Combustion air pipe must have the same diameter as vent
pipe.
Concentric Vent/Combustion Air Termination Kit (Direct Vent/
2-Pipe System Only)
Determine an appropriate location for termination kit using the
guidelines provided in section
″
Vent Termination: General
″
in this
instruction.
1. Cut one 4-in. diameter hole for 2-in. kit, or one 5-in. diameter
hole for 3-in. kit.
2. Loosely assemble concentric vent/combustion air termination
components together using instructions in kit.
3. Slide assembled kit with rain shield REMOVED through hole.
NOTE:
Do not allow insulation or other materials to accumulate
inside of pipe assembly when installing it through hole.
Roof terminations—Locate assembly through roof to appro-
priate height as shown in Fig. 43 and 44.
Sidewall terminations—Locate assembly through sidewall
with rain shield positioned no more than 1-in. from wall as
shown in Fig. 43 and 44.
4. Disassemble loose pipe fittings. Clean and cement using same
procedures as used for system piping.
5. Check required dimensions as shown in Fig. 43.
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