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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 31.
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 37 show typical
terminations.
1.
Exhaust and intake exits must be in same pressure
zone. Do not exit one through the roof and one on the
side. Also, do not exit the intake on one side and the
exhaust on another side of the house or structure.
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
piping. See Table 10.
Capacity
Exhaust Pipe Size
*045, *070
2" (51 mm), 2-1/2"
(64 mm), 3" (76 mm)
*090
*045, 070 and 090 units with the flush-mount termination must
use the 1-1/2" accelerator supplied with the kit.
Table 10. 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 Figure 31.
NOTE: Care must be taken to avoid recirculation of
exhaust back into intake pipe.
Page 26 of 55
Termination Pipe
Size
1-1/2" (38 mm)
2" (51 mm)
Issue 2223
2" EXTENSION
FOR 2" PVC PIPE
1" EXTENSION
FOR 3" PVC PIPE
FURNACE
INTAKE PIPE
Figure 29. Flush Mount Side Wall Termination
12" (305MM)
ABOVE AVE.
SNOW
ACCUMULATION
3" (76MM) OR
2" (51MM) PVC
PROVIDE SUPPORT
FOR EXHAUST LINES
Figure 30. Non-Direct Vent Roof Termination Kit
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 31.
7.
If intake and exhaust piping must be run up a side
wall to position above snow accumulation or other
obstructions, piping must be supported every 24" (610
mm) as shown in Figure 31.
When exhaust and intake piping must be run up an
outside wall, the exhaust piping must be terminated
with pipe sized per Table 9. The intake piping may be
equipped with a 90° elbow turndown. Using turndown
will add 5 feet (1.5 m) to the equivalent length of the
pipe.
8.
Based on the recommendation of the manufacturer, a
multiple furnace installation may use a group of up to
four terminations assembled together horizontally, as
shown in Figure 36.
51W11
FURNACE
4''
EXHAUST
PIPE
GLUE EXHAUST
END FLUSH INTO
TERMINATION
FLAT SIDE
1−1/2" ACCELERATOR
(
all −45, −070 and −090 units)
SIZE PER EXHAUST PIPE
TERMINATION SIZE
REDUCTION TABLE
UNCONDITIONED
ATTIC SPACE
507769-05G / 31-5000656
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