Page 44
Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations
NOTE
- In Direct Vent installations, combustion air is tak
en from outdoors and flue gases are discharged to out
doors.
NOTE
- Flue gas may be slightly acidic and may adversely
affect some building materials. If any vent termination is
used and the flue gasses may impinge on the building ma
terial, a corrosion-resistant shield (minimum 24 inches
square) should be used to protect the wall surface. If the
optional tee is used, the protective shield is recommended.
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 29.
Intake and exhaust pipes may be routed either horizontally
through an outside wall or vertically through the roof. In at
tic or closet installations, vertical termination through the
roof is preferred. Figures 26 through 34 show typical termi
nations.
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 illus
trations). Maximum separation is 3” (76MM) on roof
terminations and 6” (152MM) on side wall termina
tions.
NOTE
- When venting in different pressure zones, the
maximum separation requirement of intake and ex
haust pipe DOES NOT apply.
3. On roof terminations, the intake piping should termi
nate straight down using two 90° elbows (See figure
26).
4. Exhaust piping must terminate straight out or up as
shown. A reducer may be required on the exhaust pip
ing at the point where it exits the structure to improve
the velocity of exhaust away from the intake piping.
See table 24.
FIGURE 26
UNCONDITIONED
ATTIC SPACE
1/2” (13MM) FOAM
INSULATION IN
UNCONDITIONED
SPACE
SIZE TERMINATION
PIPE PER TABLE 24.
3”(76MM) MAX.
12” (305MM) ABOVE
AVERAGE SNOW
ACCUMULATION
3” (76MM) OR
2” (51MM) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8” (203MM) MIN
Inches(MM)
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
TABLE 24
EXHAUST PIPE TERMINATION SIZE REDUCTION
SL297UHNV
MODEL
Termination
Pipe Size
*040 and 060
1-1/2” (38MM)
*080
2” (51MM)
*SL297UHNV-040, -060 and -080 units with the flush mount
termination must use the 1-1/2”accelerator supplied with the
kit.
NOTE
- Care must be taken to avoid recirculation of ex
haust back into intake pipe.
FIGURE 27
Exhaust
Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zones)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 28
Roof Terminated
Exhaust Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zones)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
5. On field-supplied terminations for side wall exit, ex
haust piping may extend a maximum of 12 inches
(305MM) for 2” PVC and 20 inches (508MM) for 3”
(76MM) PVC beyond the outside wall. Intake piping
should be as short as possible. See figure 29.
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 29.
7. If intake and exhaust piping must be run up a side wall
to position above snow accumulation or other ob
structions, piping must be supported. At least one
bracket must be used within 6” from the top of the el
bow and then every 24” (610mm) as shown in figure
29, to prevent any movement in any direction. When
exhaust and intake piping must be run up an outside
wall, the exhaust piping must be terminated with pipe
