15
4. Use a knockout tool to create a 3" diameter hole
5. Install combustion air flange and secure with screws
removed in step one.
NON-DIRECT VENT (SINGLE PIPE) PIPING
Non-direct vent installations require only a vent/flue pipe. The
vent pipe can be run horizontally with an exit through the side of
the building or run vertically with an exit through the roof of the
building. The vent can also be run through an existing unused
chimney; however, it must extend a minimum of 12 inches above
the top of the chimney. The space between the vent pipe and the
chimney must be closed with a weather-tight, corrosion-resistant
flashing.
Although non-direct vent installations do not require a combustion
air intake pipe, a minimum of one 90° elbow should be attached to
the furnace’s combustion air intake if: an upright installation uses
the standard intake location, or a horizontal installation uses the
alternate air intake location. This elbow will guard against inad-
vertent blockage of the air intake.
VENT/FLUE PIPE LENGTHS AND DIAMETERS
(For Installations At or Above 7,000 Feet using 3” Venting)
NOTE: If either a 90 degree or 45 degree elbow is used for
termination, it must be pointed downward.
Refer to the Direct and Non-Direct Vent Table for applicable length,
elbows, and pipe diameter for construction of the vent/flue pipe
system of a non-direct vent installation. In addition to the vent/
flue pipe, a single 90° elbow should be secured to the combustion
air intake to prevent inadvertent blockage. The tee used in the
vent/flue termination must be included when determining the num-
ber of elbows in the piping system.
VENT/FLUE PIPE TERMINATIONS
NOTE: If either a 90 degree or 45 degree elbow is used for
termination, it must be pointed downward.
The vent/flue pipe may terminate vertically, as through a roof, or
horizontally, as through an outside wall.
Vertical vent/flue pipe terminations should be as shown in the fol-
lowing figure. Refer to Vent/Flue Pipe and Combustion Air Pipe -
Termination Locations for details concerning location restrictions.
The penetration of the vent through the roof must be sealed tight
with proper flashing such as is used with a plastic plumbing vent.
Horizontal vent/flue pipe terminations should be as shown in the
following figure. Refer to Vent/Flue Pipe and Combustion Air Pipe.
To secure the pipe passing through the wall and prohibit damage to
piping connections, a coupling should be installed on either side of
the wall and solvent cemented to a length of pipe connecting the
two couplings. The length of pipe should be the wall thickness plus
the depth of the socket fittings to be installed on the inside and
outside of the wall. The wall penetration should be sealed with silicone caulking material.
NOTE: Terminate both pipes in the same pressure zone (same side of roof, no major obstacles between pipes, etc.).
B
E
SURE
NOT
TO
DAMAGE
INTERNAL
WIRING
OR
OTHER
COMPONENTS
WHEN
REINSTALLING
COUPLING
AND
SCREWS
.
CAUTION
MODEL
PIPE
SIZE
12345678
2
^
145 140 135 130 125 120 115 110
3 168 161 154 147 140 133 126 119
25550454035302520
3 127 120 113 106 99 92 85 78
2
^
30 25 20 15 10 5 N/A N/A
3
^
72 65 58 51 44 37 30 23
2
^
30 25 20 15 10 5 N/A N/A
3
^
72 65 58 51 44 37 30 23
2
^
40 35 30 25 20 15 10 5
37265585144373023
26055504540353025
3 168 161 154 147 140 133 126 119
23025201510 5N/AN/A
3 113 106 99 92 85 78 71 64
2 N/A N/A N/A N/A N/A N/A N/A N/A
36558514437302316
2 100 95 90 85 80 75 70 65
3 137 130 123 116 109 102 95 88
26055504540353025
3 127 120 113 106 99 92 85 78
2353025201510 5N/A
3 160 153 146 139 132 125 118 111
2 N/A N/A N/A N/A N/A N/A N/A N/A
3 127 120 113 106 99 92 85 78
7,000 ft altitude or above use 3" pipe
^
*MSS920402BN - add 20' of 2" pipe for upflow position
^
*MSS920803BN - add 10' of 2" pipe for upflow position, add 66' of 3" pipe for upflow position
^
*MSS920804CN - add 25' of 2" pipe for upflow position, add 58' of 3" pipe for upflow position
^ *MSS920805CN - add 15' of 2" pipe for upflow position, add 58' of 3" pipe for upflow position
MODEL
PIPE
SIZE
12345678
2
^
100 95 90 85 80 75 70 65
3 168 161 154 147 140 133 126 119
24540353025201510
3 168 161 154 147 140 133 126 119
2
^
35 30 25 20 15 10 5 N/A
3 168 161 154 147 140 133 126 119
26055504540353025
3 113 106 99 92 85 78 71 64
24540353025201510
3 120 113 106 99 92 85 78 71
240353025201510 5
3 151 144 137 130 123 116 109 102
2 N/A N/A N/A N/A N/A N/A N/A N/A
3 158 151 144 137 130 123 116 109
2 100 95 90 85 80 75 70 65
3 137 130 123 116 109 102 95 88
24540353025201510
3 168 161 154 147 140 133 126 119
240353025201510 5
3 120 113 106 99 92 85 78 71
2 N/A N/A N/A N/A N/A N/A N/A N/A
3 113 106 99 92 85 78 71 64
2 N/A N/A N/A N/A N/A N/A N/A N/A
3 110 103 96 89 82 75 68 61
7,000 ft altitude or above use 3" pipe
^ *MSS960402BN - add 25' of 2" pipe for upflow position
^
*MSS960803BN - add 20' of 2" pipe for upflow position
Number of Elbows
*MSS920402BN
*MSS920603BN
*MSS921004CN
*MSS960603BN
*MSS920803BN
*MSS920804CN
*MSS920805CN
*CSS920804CN
*CSS921005CN
*MSS960402BN
*MSS921005CN
*MSS921205DN
*CSS920402BN
*CSS920603BN
*MSS960804CN
*MSS960805CN
*MSS961005CN
*CSS961005CN
*MSS960803BN
*CSS961205DN
*MSS961205DN
*CSS960402BN
*CSS960603BN
*CSS960804CN
*MSS9* / *CSS9 Direct Vent (2-Pipe) & Non-Direct Vent (1-Pipe)
Maximum Allowable Length of Vent/FLue Pipe
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