Lennox ML296UH045XV36B - Details of Exhaust Piping Terminations for Direct Vent Installations

Page 35
Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
NOTE - In Direct Vent installations, combustion air is taken
from outdoors and ue gases are discharged to outdoors.
NOTE - Flue gas may be slightly acidic and may adverse-
ly aect some building materials. If any vent termination
is used and the ue gasses may impinge on the building
material, a corrosion-resistant shield (minimum 24 inches
square) should be used to protect the wall surface. If the
optional tee is used, the protective shield is recommend-
ed. The shield should be constructed using wood, plastic,
sheet metal or other suitable material. All seams, joints,
cracks, etc. in the aected area should be sealed using an
appropriate sealant. See FIGURE 37.
Intake and exhaust pipes may be routed either horizontal-
ly through an outside wall or vertically through the roof. In
attic or closet installations, vertical termination through the
roof is preferred. FIGURE 29 through FIGURE 36 shows
typical terminations.
1 - Vent terminations are not required to be in the same
pressure zone. You may exit the intake on one side
of the structure and the exhaust on another side
(FIGURE 30). You may exit the exhaust out the roof
and the intake out the side of the structure (FIGURE
31).
2 - Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to
illustrations). Maximum separation is 3” (76mm)
on roof terminations and 6” (152mm) on side wall
terminations.
NOTE - When venting in dierent pressure zones,
the maximum separation requirement of intake and
exhaust pipe DOES NOT apply.
3 - On roof terminations, the intake piping should
terminate straight down using two 90° elbows (See
FIGURE 29).
4 - Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust
piping at the point where it exits the structure to
improve the velocity of exhaust away from the
intake piping. See TABLE 17.
5 - On eld-supplied terminations for side wall exit,
exhaus piping may extend a maximum of 12 inches
(305mm) for 2” PVC and 20 inches (508mm) for 3”
(76mm) PVC beyond the outside wall. Intake piping
should be as short as possible. See FIGURE 37.
NOTE - Care must be taken to avoid recirculation of
exhaust back into intake pipe.
6 - On eld supplied terminations, a minimum distance
between the end of the exhaust pipe and the end of
the intake pipe without a termination elbow is 8” and
a minimum distance of 6” with a termination elbow.
See FIGURE 37.
UNCONDITIONED
ATTIC SPACE
3”(76mm) MAX.
12” (305mm) ABOVE
AVERAGE SNOW
ACCUMULATION
3” (76mm) OR
2” (51mm) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8” (203mm) MIN
Inches(mm)
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 29
Exhaust
Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 30
Roof T
erminated
Exhaust Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 31
TABLE 17
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML296UHV Model Termination Pipe Size
*045 and 070 1-1/2” (38MM)
*090 2” (51MM)
110 2” (51MM)
*ML296UHV-045, -070 and -090 units with the ush mount termination
must use the 1-1/2”accelerator supplied with the kit.