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Details of Intake and Exhaust Piping Terminations
for Direct Vent Installations
NOTE: In Direct Vent installations, combustion air is taken
from outdoors and flue gases are discharged to outdoors.
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 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 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.
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. Figure 29 through Figure 34 show typical
terminations.
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 27). You may exit the exhaust out the roof
and the intake out the side of the structure (Figure 28).
Exhaust
Furnace
Pipe
Figure 27. Exiting Exhaust and Intake Vent
(no common pressure zone)
Roof T erminated
Exhaust Pipe
Figure 28. Exiting Exhaust and Intake Vent
(no common pressure zone)
Inlet Air
Minimum 12 in.
(305MM) above
grade or snow
accumulation
Inlet Air
Minimum 12 in.
Furnace
(305MM) above
grade or snow
accumulation
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 different 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 (Figure 29).
Inches (MM)
8" (203MM) MIN
12" (305MM) ABOVE
AVERAGE SNOW
ACCUMULATION
3" (76MM) OR
2" (51MM) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
Figure 29. Direct Vent Roof Termination
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 22.
NOTE: Care must be taken to avoid recirculation of
exhaust back into intake pipe.
Model
Exhaust Pipe Size Termination Pipe Size
*070
*090
2", 2-1/2", or 3"
110
135
* -070 and -090 units with the flush-mount termination must
use the 1-1/2" accelerator supplied with the kit.
Table 22. Exhaust Pipe Termination Size Reduction
5. 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. Intake piping should be as short
as possible. See Figure 35.
6. On field-supplied terminations, a minimum distance
Page 44
3" (76MM) MIN.
SIZE PER EXHAUST PIPE
TERMINATION SIZE
REDUCTION TABLE
UNCONDITIONED
ATTIC SPACE
1/2" (13MM) FOAM
INSULATION IN
UNCONDITIONED
SPACE
1-1/2"
2"
3"
31-5000723 Rev. 0
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