Lennox MERIT ML195UH Installation Instructions Manual page 22

Intake Piping
The ML195UH furnace may be installed in either direct
vent or non-direct vent applications. In non-direct vent ap-
plications, when intake air will be drawn into the furnace
from the surrounding space, the indoor air quality must be
considered and guidelines listed in Combustion, Dilution
and Ventilation Air section must be followed.
Follow the next two steps when installing the unit in Direct
Vent applications, where combustion air is taken from out-
doors and flue gases are discharged outdoors. The pro-
vided air intake screen must not be used in direct vent
applications (outdoors).
1 - Use transition solvent cement or a sheet metal screw
to secure the intake pipe to the inlet air connector.
2 - Route piping to outside of structure. Continue with
installation following instructions given in general
guide lines for piping terminations and intake and
exhaust piping terminations for direct vent sections.
Refer to table 5 for pipe sizes.
TYPICAL AIR INTAKE PIPE CONNECTIONS
UPFLOW NON−DIRECT
VENT APPLICATIONS
NOTE - Debris screen and elbow may be rotated, so that
screen may be positioned to face forward or to either side.
FIGURE 26
INTAKE
DEBRIS
SCREEN
(Provided)
Page 22
TYPICAL AIR INTAKE PIPE CONNECTIONS
HORIZONTAL NON−DIRECT VENT APPLICATIONS
(Horizontal Right−Hand Air Discharge Application Shown)
NOTE - Debris screen may be positioned straight out
(preferred) or with an elbow rotated to face down.
FIGURE 27
Follow the next two steps when installing the unit in Non-
Direct Vent applications where combustion air is taken
from indoors and flue gases are discharged outdoors.
1 - Use field-provided materials and the factory-
provided air intake screen to route the intake piping
as shown in figure 26 or 27. Maintain a minimum
clearance of 3" (76mm) around the air intake
opening. The air intake opening (with the protective
screen) should always be directed forward or to
either side in the upflow position, and either straight
out or downward in the horizontal position.
The air intake piping must not terminate too close
to the flooring or a platform. Ensure that the intake
air inlet will not be obstructed by loose insulation
or other items that may clog the debris screen.
2 - If intake air is drawn from a ventilated attic (figure
28) or ventilated crawlspace (figure 29) the exhaust
vent length must not exceed those listed in table 6.
If 3" diameter pipe is used, reduce to 2" diameter
pipe at the termination point to accommodate the
debris screen.
3 - Use a sheet metal screw to secure the intake pipe
to the connector, if desired.
PVC pipe
coupling
OR
INTAKE
DEBRIS
SCREEN
(Provided)