Page 27
Intake Piping
The ML193UHE 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
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 in
-
stallation 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
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.
Min 2”
FIGURE 27
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
Min 2”
FIGURE 28
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 or FIGURE 28. Maintain a minimum clear
-
ance 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 up
-
flow 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
29) or ventilated crawlspace (FIGURE 30) the exhaust
vent length must not exceed those listed in TABLE 15.
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.
