Direct Vent Installation—Counterflow Installations
Refer to appropriate tables for proper pipe size, vent length
and the number of elbows allowed, and air intake length and
the number of elbows allowed.
Refer to "Materials" in "Plan Vent System" for the proper
Do not install the inlet air restrictor plate in any direct vent
installation. The inlet air restrictor plate (see "Inlet Air
Restrictor Plate" in "Venting Requirements") supplied with
this furnace is to be used only in nondirect vent applications.
The flue pipe screen, designed to keep objects out of the flue
pipe (see "Flue Pipe Screen" in "Venting Requirements"),
should be installed at the termination of the flue pipe.
NOTE: Do not place an additional flue pipe screen in the
intake termination because the air intake may freeze shut.
Direct Vent—Counterflow (Horizontal Venting)
A. Run pitch =
" (6.4 mm)
per foot minimum
B. Optional piece
C. Flue pipe screen (inside
D. Flue pipe
E. 18" (45.7 cm)
F. Air intake pipe
G. 6" (15.2 cm)
H. 12" (30.5 cm) minimum clearance.
Adjust height to expected snow
level based on local conditions.
J. 3" (7.6 cm) minimum to 48"
(121.9 cm) maximum
K. Condensate collar
L. Air intake pipe
M PVC collars
For proper operation, the vent and air intake pipe must be
installed in the same pressure zone. Therefore, in horizontal
venting applications they must be on the same side of the
house within the parameters as shown.
NOTE: The 18" (45.7 cm) dimension shown in "Direct Vent
Counterflow—Horizontal Venting" is the minimum
recommended height for extremely cold areas. In these
areas, moisture in the flue gases may condense and freeze on
the air intake if this height is reduced. In milder climates, this
may be reduced to a minimum of 6" (15.2 cm). Height may be
increased as needed provided total length is not exceeded.
Direct Vent—Counterflow (Vertical Venting)
A. Flue pipe screen (inside flue pipe)
B. 24" (61 cm) minimum to roof or 12" (30.5 cm)
minimum clearance. Adjust height to
expected snow level based on local
" (16.5 cm) minimum to 24" (61 cm)
D. Storm collars
The 45,000 and 67,000 Btu/h models contain an inlet air
assembly that uses two 22.5° elbows that attach separately
from the straight inlet pipe, as shown. This allows the inlet
pipe assembly to be removed if needed for service.
F. Air intake pipe
G. Condensate collar
H. PVC collars
I. Flue pipe
J. Run pitch =
(6.4 mm) per foot