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Details of Exhaust Piping Terminations for Non-Direct 
Vent Applications
Exhaust pipes may be routed either horizontally through 
an outside wall or vertically through the roof. In attic or 
closet installations, vertical termination through the roof 
is preferred. Figure 42 and Figure 43 show typical termi-
nations.
1 -   Exhaust piping must terminate straight out or up as 
shown. The termination pipe must be sized as listed 
in  table  8.The  specied  pipe  size  ensures  proper 
velocity required to move the exhaust gases away 
from the building.
2 -   On  eld  supplied  terminations  for  side  wall  exit, 
exhaust piping may extend a maximum of 12 inches 
(305MM) for 2” PVC and 20 inches (508MM) for 3” 
(76MM) PVC beyond the outside wall.
NON-DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
UNCONDITIONED
ATTIC SPACE
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR EXHAUST LINES
12” (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
Figure 42 
3 -   If exhaust piping must be run up a side wall 
to position above snow accumulation or other 
obstructions, piping must be supported every 24 
inches (610MM). When exhaust piping must be run 
up an outside wall, any reduction in exhaust pipe 
size must be done after the nal elbow.
4 -   Distance between exhaust pipe terminations on 
multiple furnaces must meet local codes.
Crawl Space and Extended Horizontal Venting
Lennox provides kit 51W18 (USA) and kit 15Z70 (Cana-
da) to install 2” or 3” PVC exhaust piping through the oor 
joists and into the the crawl space. See Figure 44.
This kit can also be used as a supplemental drain for in-
stallations with condensate run back in the vent pipe (ie. 
long horizontal runs, unconditioned spaces, etc.).
      DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
NOTE - Do 
tical discharge through an existing unused chimney or stack is required, insert piping
inside 
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
8” - 12”
(203mm - 305mm)
3” - 8”
(76mm-
203mm)
3” - 8”
(76mm-
203mm)
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE *
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
ALTERNATE
INTAKE PIPE
INTAKE PIPE
INSULATION (optional)
EXTERIOR
PORTION OF
CHIMNEY
INSULATE
TO FORM
SEAL
SHEET
METAL TOP
PLATE
*SIZE TERMINATION
PIPE PER TABLE 7.
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
Figure 43 
Venting In A Crawl Space
KIT 51W18
(USA)
Basement Floor
KIT 15Z70
(CANADA)
Figure 44