Page 38
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 pre
ferred. Figures 37 and 38 show typical terminations.
1. Exhaust piping must terminate straight out or up as
shown. The termination pipe must be sized as listed in
table 17.The specified pipe size ensures proper
velocity required to move the exhaust gases away
from the building.
2. On field supplied terminations for side wall exit, ex
haust piping may extend a maximum of 12 inches
(305MM) for 2” PVC and 20 inches (508MM) for 3”
(76MM) PVC beyond the outside wall.
FIGURE 37
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
3. If exhaust piping must be run up a side wall to position
above snow accumulation or other obstructions, pip
ing 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 final elbow.
4. Distance between exhaust pipe terminations on mul
tiple furnaces must meet local codes.
Crawl Space and Extended Horizontal Venting
Lennox provides kit 51W18 to install 2” or 3” PVC exhaust
piping through the floor joists and into the the crawl space.
See figure 39.
This kit can also be used as a supplemental drain for instal
lations with condensate run back in the vent pipe (ie. long
horizontal runs, unconditioned spaces, etc.).
NOTE - Do not discharge exhaust gases directly into any chimney or vent stack. If ver
tical discharge through an existing unused chimney or stack is required, insert piping
inside chimney until the pipe open end is above top of chimney and terminate as illus
trated. In any exterior portion of chimney, the exhaust vent must be insulated.
FIGURE 38
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
EXTERIOR
PORTION OF
CHIMNEY
INSULATE
TO FORM
SEAL
SHEET
METAL TOP
PLATE
ML296UHV NON-DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
Minimum 12” (305MM)
above chimney top
plate or average snow
accumulation
FIGURE 39
Venting In A Crawl Space
KIT 51W81
(USA)
Basement Floor
KIT 51W81
(CANADA)
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