Lennox Allied Air A96UHMV Installation Instructions Manual page 20

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. Figures 23 through 29 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). Maximum separation is 3" (76 mm) on
roof terminations and 6" (152 mm) on sidewall
terminations.
3. On roof terminations, the intake piping should terminate
straight down using two 90° elbows (See Figure 23).
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 6.
NOTE: Care must be taken to avoid recirculation of exhaust
back into intake pipe.
DIRECT VENT ROOF TERMINATION KIT
Figure 23
Page 20 of 66
FIELD SUPPLIED WALL TERMINATION OR
See venting Table 5 for maximum venting lengths with this
arrangement.
* Use wall support every 24" (610 mm). Use two wall supports if
extension is greater than 24" (610 mm) but less than 48" (1219 mm).
NOTE: One wall support must be 6" (152 mm) from top of each pipe
(intake and exhaust).
Issue 1230
Figure 24
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