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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 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 32.
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 28 through 38 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
29). You may exit the exhaust out the roof and the intake
out the side of the structure (Figure 30).
2. Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to
illustrations). Maximum 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 28).
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 9.
Exhaust Pipe Termination Size Reduction
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 Figures 33 and 34.
NOTE: Care must be taken to avoid recirculation of exhaust
back into intake pipe.
507052-04
Table 9
Direct Vent Roof Termination Kit
Issue 1621
Figure 28
Figure 29
Figure 30
Page 25 of 58
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