Lennox MERIT Series Installation Instructions Manual page 29

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 39 and FIGURE 40 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.
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.
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 39
STRAIGHT-CUT OR
ANGLE-CUT IN DIRECTION
OF ROOF SLOPE
SHOULDER OF FITTINGS
PROVIDE SUPPORT
OF PIPE ON TOP PLATE
EXTERIOR
PORTION OF
CHIMNEY
12" (305mm)
ABOVE AVE.
SNOW
ACCUMULATION
3" (76mm) OR
2" (51mm) PVC
PROVIDE SUPPORT
FOR EXHAUST LINES
NON-DIRECT VENT ROOF TERMINATION KIT
Crawl Space and Extended Horizontal Venting
Lennox provides a crawl space vent kit to install 2" or 3"
PVC exhaust piping through the floor joists and into the
crawl space. See the figure below.
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 29
UNCONDITIONED
ATTIC SPACE
(15F75 or 44J41)
FIGURE 40
KIT 51W18
(USA)
KIT 15Z70
(CANADA)
FIGURE 41