Lennox MERIT Series Installation Instructions Manual page 27

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 40 and FIGURE 41 show typical ter-
minations.
1 - Exhaust piping must terminate straight out or up
as shown. The termination pipe must be sized as
listed in TABLE 10.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,
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.
12" (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
3" (76mm) OR
2" (51mm) PVC
PROVIDE SUPPORT
FOR EXHAUST LINES
NON-DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 40
NON-DIRECT VENT APPLICATION
USING EXISTING CHIMNEY
Minimum 12" (305MM)
above chimney top
plate or average snow
accumulation
SHEET
METAL TOP
PLATE
INSULATE
TO FORM
SEAL
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.
FIGURE 41
UNCONDITIONED
ATTIC SPACE
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
EXTERIOR
PORTION OF
CHIMNEY
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 final elbow.
4 - Distance between exhaust pipe terminations on
multiple 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 crawl space.
See FIGURE 42.
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.).
Venting In A Crawl Space
Basement Floor
Page 27
KIT 51W18
(USA)
KIT 15Z70
(CANADA)
FIGURE 42