Page 30
Intake Piping
The ML296UHV furnace may be installed in either direct
vent or non-direct vent applications. In non-direct vent
applications, 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
outdoors and flue gases are discharged outdoors. The
provided 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
guidelines for piping terminations and intake and ex
haust piping terminations for direct vent sections. Re
fer to table
14 for pipe sizes.
FIGURE 21
TYPICAL AIR INTAKE PIPE CONNECTIONS
UPFLOW NON−DIRECT
VENT APPLICATIONS
INTAKE
DEBRIS
SCREEN
(Provided)
NOTE - Debris screen and elbow may be rotated, so that
screen may be positioned to face forward or to either side.
FIGURE 22
TYPICAL AIR INTAKE PIPE CONNECTIONS
HORIZONTAL NON−DIRECT VENT APPLICATIONS
(Horizontal Right−Hand Air Discharge Application Shown)
INTAKE
DEBRIS
SCREEN
(Provided)
OR
NOTE - Debris screen may be positioned straight out
(preferred) or with an elbow rotated to face down.
coupling
PVC pipe
Follow the next two steps when installing the unit in Non‐
Direct Vent applications where combustion air is taken
from indoors or ventilated attic or crawlspace 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 21 or 22. 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 23)
or ventilated crawlspace (figure 24) the exhaust vent
length must not exceed those listed in table 15. If 3” di
ameter 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.
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