Page 31
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 40.
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 33 through 41 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 34). You may exit the exhaust out the roof
and the intake out the side of the structure (figure 35).
NOTE
- When venting in different pressure zones,
maximum separation of intake and exhaust pipe DO
NOT apply.
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
33).
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 15.
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.
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.
NOTE
- Care must be taken to avoid recirculation of
exhaust back into intake pipe.
TABLE 15
EXHAUST PIPE TERMINATION SIZE REDUCTION
ML193UHE
MODEL
Termination
Pipe Size
*030, 045 and 070
1-1/2” (38mm)
*090
2” (51mm)
110
2” (51mm)
*ML193UHE-030-, 045, -070 and -090 units with the flush mount termina
tion must use the 1-1/2” accelerator supplied with the kit unless a tee is used
for termination as shown figure 40.
FIGURE 33
UNCONDITIONED
ATTIC SPACE
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)
FIGURE 34
Exhaust
Pipe
Furnace
Exiting Exhaust and Intake Vent
(different pressure zones)
Inlet Air
(Minimum 12 in.
305 MM) above
grade or snow
accumulation
FIGURE 35
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
