Lennox G51MP SERIES Installation Instructions Manual page 27

Details of Intake and Exhaust Piping Terminations for
Direct Vent Installations (Figure 30)
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 an outside wall or vertically through the roof. In at-
tic or closet installations, vertical termination through the
roof is preferred. Figures 31 through 39 show typical ter-
minations.
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 il-
lustrations). Maximum separation is 3" (76mm) on roof
terminations and 6" (152mm) on side wall termina-
tions.
3 − If necessary, install a field−provided reducer to adapt
larger vent pipe size to termination pipe size.
4 − On roof terminations, the intake piping should termi-
nate straight down using two 90° elbows (See figure
31).
5 − Exhaust piping must terminate straight out or up as
shown. In rooftop applications, a reducer may be re-
quired 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 8.
NOTE − Care must be taken to avoid recirculation of
exhaust back into intake pipe.
TABLE 8
EXHAUST PIPE TERMINATION SIZE REDUCTION
G51MP
Exhaust Pipe Size
MODEL
045 and 070 2", 2−1/2", 3" or 4"
090 2", 2−1/2", 3" or 4"
110 2", 2−1/2", 3" or 4"
135 3" or 4"
*Approved 3" concentric termination kit terminates with 2−5/8" ID pipe.
3(76) MAX.
Inches(mm)
8" (203) MIN
12" (305) ABOVE
AVERAGE SNOW
ACCUMULATION
3" (76) OR
2" (51) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
DIRECT VENT ROOF TERMINATION KIT
(15F75 or 44J41)
FIGURE 31
Termination Pipe Size
1−1/2"
2"
*2"
*2"
SIZE TERMINATION
PIPE PER TABLE 8.
UNCONDITIONED
ATTIC SPACE
1/2" (13) FOAM
INSULATION IN
UNCONDITIONED
SPACE
Page 27
1/2 (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
FIELD−
PROVIDED
REDUCER MAY
BE REQUIRED
TO ADAPT
LARGER VENT
PIPE SIZE TO
TERMINATION
OUTSIDE
WALL
Inches (mm)
TOP VIEW WALL RING KIT WITH STRAIGHT INTAKE
(15F74)
1/2 (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
FIELD−
PROVIDED
REDUCER MAY
BE REQUIRED
TO ADAPT
LARGER VENT
PIPE SIZE TO
TERMINATION
Inches (mm)
OUTSIDE
WALL
TOP VIEW WALL RING KIT WITH 90° ELBOW ON INTAKE
(15F74)
FIGURE 32
6 − On field supplied terminations for side wall exits, ex-
haust piping should extend a maximum of 12 inches
(305mm) beyond the outside wall. Intake piping
should be as short as possible. See figure 32.
7 − On field supplied terminations, a minimum separation
distance between the end of the exhaust pipe and the
end of the intake pipe is 8 inches (203mm).
8 − If intake and exhaust piping must be run up a side wall
to position above snow accumulation or other obstruc-
tions, piping must be supported every 3 ft. (.9m) as
shown in figure 22. Refer to figure 35 for proper piping
method. In addition, WTK wall termination kit must be
extended for use in this application. See figure 38.
When exhaust and intake piping must be run up an
outside wall, the exhaust piping must be terminated
with pipe sized per table 8. The intake piping may be
equipped with a 90° elbow turndown. Using turndown
will add 5 feet (1.5m) to the equivalent length of the
pipe.
9 − Based on the recommendation of the manufacturer, a
multiple furnace installation may use a group of up to
four termination kits WTK assembled together hori-
zontally, as shown in figure 37.
12 (305) MAX.
1/2" (13)
ARMAFLEX
INSULATION
6 (152)
SIZE
MAXIMUM
TERMINATION
PIPE PER
TABLE 8.
2 (51) PVC
COUPLING
8 (203)
MINIMUM
12 (305) MAX.
1/2" (13)
ARMAFLEX
INSULATION
6 (152)
SIZE
MAXIMUM
TERMINATION
PIPE PER
TABLE 8.
4 (102)
MINIMUM