Lennox ML193DFE Series Unit Information page 27

Intake Piping
The ML193DFE 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. 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
outdoors and flue gases are discharged outdoors. The
provided air intake screen must not be used in direct
vent applications (outdoors).
1 - Use cement 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 13 for pipe sizes.
TYPICAL AIR INTAKE PIPE CONNECTIONS
NON−DIRECT VENT APPLICATIONS
SCREEN
(Provided)
NOTE - Air intake screen and elbow may be rotated, so that
screen may be positioned to face forward or to either side.
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 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 sideways.
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 14. If 3" diameter pipe is used, reduce
to 2" diameter pipe at the termination point to
accommodate the debris screen.
3 - Use cement to secure the intake pipe to the
connector, if desired.
AIR
INTAKE
If this unit is being installed in an application with
combustion air coming in from a space serviced by
an exhaust fan, power exhaust fan, or other device
which may create a negative pressure in the space,
take care when sizing the inlet air opening. The
inlet air opening must be sized to accommodate
the maximum volume of exhausted air as well as
themaximum volume of combustion air required for
all gas appliances serviced by this space.
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Attic and Outlet Air to Outside)
Roof Terminated
Exhaust Pipe
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm
hour of the total input rating of all equipment in the enclosure.
EQUIPMENT IN CONFINED SPACE
(Inlet Air from Ventilated Crawlspace and Outlet Air to Outside)
Roof Terminated
Exhaust Pipe
Ventilation
Furnace
Louvers
(Crawl space)
Coupling or
3 in. to 2 in.
Transition
(Field Provided)
NOTE-The inlet and outlet air openings shall each have a free area
of at least one square inch per 4,000 Btu (645mm
hour of the total input rating of all equipment in the enclosure.
Page 27
CAUTION
Ventilation Louvers
Inlet Air
(Minimum
12 in.(305mm) Above
attic floor)
*Intake Debris
Screen
(Provided)
Furnace
2
per 1.17kW) per
FIGURE 28
Inlet Air
(Minimum
12 in.(305mm)
Above crawl
space floor)
*Intake Debris Screen Provided)
2
per 1.17kW) per
FIGURE 29