Page 35
31-5000728 Rev. 0
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 44.
Intake and exhaust pipes may be routed either horizontally
through and outside wall or vertically through the roof. In
attic or closet installations, vertical termination through the
roof is preferred. Figure 33 through Figure 40 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 34). You may exit the exhaust out the roof
and the intake out the side of the structure (Figure 35).
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 sidewall
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 (see Figure 33).
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 12.
Capacity
Exhaust Pipe Size
Termination
Pipe Size
045 & 070
2” (51mm), 2-1/2” (64mm),
3” (76mm)
1-1/2” (38mm)
90
2” (51mm)
110
NOTE: -030, -045, -070 and -090 units with the flush mount
termination must use the 1-1/2” accelerator supplied with the
kit.
Table 12. Exhaust Pipe Termination Size Reduction
NOTE:
Care must be taken to avoid recirculation of
exhaust back into intake pipe.
5.
On field supplied terminations for sidewall 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 34.
Figure 33. Direct Vent Roof Termination
Figure 34. Exiting Exhaust and Intake Vent
(no common pressure zone)
Figure 35. Exiting Exhaust and Intake Vent
(no common pressure zone)
Size per Exhaust Pipe
Termination Size
Reduction Table
3” (76mm) Min.
8” (203mm) Min.
Unconditioned
Attic Space
1/2” (13mm)
Foam Insulation in
Unconditioned Space
Provide Support
for Intake and
Exhaust Lines
3” (76mm) or
2” (51mm) PVC
12” (305mm) Above
Average Snow
Accumulation
Inlet Air
Minimum 12”
(305mm) above
grade or snow
accumulation
Exhaust
Pipe
Furnace
Inlet Air
Minimum 12”
(305mm) above
grade or snow
accumulation
Roof Terminated
Exhaust Pipe
Furnace
