507962-01
Page 26 of 53
Issue 2149
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 gases may impinge on the building
material, a corrosion-resistant shield (minimum 24 inches
square) must be used to protect the wall surface. If the
optional tee is used, the protective shield is required.
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 38.
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 30 through Figure 37 show 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
31). You may exit the exhaust out the roof and the
intake out the side of the structure (Figure 32).
2. Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to
illustrations). Minimum separation is 3” (76 mm)
on roof terminations and 6” (152 mm) on side wall
terminations.
3. On roof terminations, the intake piping should terminate
straight down using two 90° elbows (see Figure 30).
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
Table 9.
Exhaust Pipe Termination Size Reduction
Capacity
Exhaust Pipe Size
Termination
Pipe Size
*045 and *070
2” (51 mm),
2-1/2” (64 mm),
3” (76 mm)
1-1/2” (38 mm)
*090
2” (51 mm)
110
3” (76 mm)
*045, 070 and 090 units with the flush-mount termination must
use the 1-1/2” accelerator supplied with the kit.
5. On field supplied terminations for side wall exit,
exhaust piping may extend a maximum of 12 inches
(305 mm) for 2” PVC and 20 inches (508 mm) for 3”
(76 mm) PVC beyond the outside wall. Intake piping
should be as short as possible. See Figure 38.
NOTE:
Care must be taken to avoid recirculation of
exhaust back into intake pipe.
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
Figure 30. Direct Vent Roof Termination Kit
(15F75 or 44J41)
UNCONDITIONED
ATTIC SPACE
SIZE PER EXHAUST PIPE
TERMINATION SIZE
REDUCTION TABLE
3” (76MM) MIN.
12” (305MM) ABOVE
AVERAGE SNOW
ACCUMULATION
3” (76MM) OR
2” (51MM) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8” (203MM) MIN
Inches (MM)
1/2” (13MM) FOAM
INSULATION IN
UNCONDITIONED
SPACE
Figure 31. Exiting Exhaust and Intake Vent
(no common pressure zone)
Exhaust
Pipe
Furnace
Inlet Air
Minimum 12 in.
(305MM) above
grade or snow
accumulation
Figure 32. Exiting Exhaust and Intake Vent
(no common pressure zone)
Roof Terminated
Exhaust Pipe
Furnace
Inlet Air
Minimum 12 in.
(305MM) above
grade or snow
accumulation
