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Conditioned
Space
Figure 25. Insulating Exhaust Pipe in an
Unconditioned Space
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.
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 26 through Figure 32 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).
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 26).
4.
Exhaust piping must terminate straight out or up as
shown. A reducer is 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 7A through Table 7B.
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 24.
6.
On field supplied terminations, a minimum distance
between the end of the exhaust pipe and the end of
Page 22 of 73
Conditioned
Space
Exhaust
Pipe Insulation
Unconditioned
Space
the intake pipe without a termination elbow is 8" and a
minimum distance of 6" with a termination elbow. See
Figure 24.
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 24. In addition, close
coupled wall termination must be extended for use
Pipe
in this application. Exhaust and intake piping that is
run up a wall is considered to be in an unconditioned
Intake
space, so piping should be sized according to Table 8.
Pipe
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.
Unit
070*
090*
110
*070 and 090 units installed with flush mount termination must
use the 1-1/2" accelerator supplied with the kit.
Table 9. Exhaust Pipe Termination Size Reduction
Inches (MM)
12" (305MM) ABOVE
AVERAGE SNOW
ACCUMULATION
2" (51MM) PVC
Figure 26. Direct Vent Roof Termination Kit
Figure 27. Exiting Exhaust and Intake Vent
Issue 2241
Exhaust Pipe Size
2", 2-1/2", or 3"
2", 2-1/2", or 3"
2-1/2" or 3"
3" (76MM) MIN.
8" (203MM) MIN
3" (76MM) OR
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
(15F75 or 44J41)
Termination Pipe
Size
1-1/2"
2"
2"
SIZE PER EXHAUST PIPE
TERMINATION SIZE
REDUCTION TABLE
UNCONDITIONED
ATTIC SPACE
1/2" (13MM) FOAM
INSULATION IN
UNCONDITIONED
SPACE
507029-05
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