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Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
NOTE − In Direct Vent installations, combustion air is tak-
en from outdoors and flue gases are discharged to out-
doors.
NOTE − Flue gas may be slightly acidic and may adversely
affect some building materials. If any vent termination is
used and the flue gasses may impinge on the building ma-
terial, 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 recommended.
The shield should be constructed using wood, plastic,
sheet metal or other suitable material. All seams, joints,
cracks, etc. in the affected area should be sealed using an
appropriate sealant. See figure 39.
Intake and 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. Figures 34 through 48 show typical termina-
tions.
1 − Intake and exhaust 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 35). You may exit the exhaust out the roof
and the intake out the side of the structure (figure 36).
2 − Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il-
lustrations). Maximum separation is 3" (76mm) on roof
terminations and 6" (152mm) on side wall termina-
tions.
3 − On roof terminations, the intake piping should termi-
nate straight down using two 90° elbows (See figure
34).
4 − Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust pip-
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 8.
5 − 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. Intake piping
should be as short as possible. See figures 37 and 38.
6 − On field 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
figures 37 and 38.
TABLE 8
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML193UH
MODEL
Termination
Pipe Size
*045 and 070
1−1/2" (38mm)
*090 2" (51mm)
110 2" (51mm)
135 2" (51mm)
*ML193UH−045, −070 and −090 units with the flush mount
termination must use the 1−1/2"accelerator supplied with the
kit unless a tee is used for termination as shown figure 39.
NOTE − Care must be taken to avoid recirculation of ex-
haust back into intake pipe.
FIGURE 34
UNCONDITIONED
ATTIC SPACE
1/2" (13mm) FOAM
INSULATION IN
UNCONDITIONED
SPACE
SIZE TERMINATION
PIPE PER TABLE 8.
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 35
Exhaust
Pipe
Furnace
Exiting Exhaust and Intake Vent
(no common pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 36
Roof T
erminated
Exhaust Pipe
Furnace
Exiting Exhaust and Intake Vent
(no common pressure zone)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
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