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Intake Piping
This 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. Guidelines listed in Combustion, Dilution and
Ventilation Air section must be followed.
Use the following 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 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 7A through Table 7C for pipe sizes.
Use the following 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. Maintain
a minimum clearance of 3" (76 mm) around the air
intake opening. The air intake opening (with the
protective screen) should always be directed forward,
or sideways.
508405-01
Pipe size determined in table 7.
2"
2"
3"
TRANSITION
*2"
* When transitioning up in pipe size, use the shortest length of 2" PVC pipe possible.
NOTE: Exhaust pipe and intake pipe must be the same diameter.
Figure 24. Typical Intake Pipe Connections (Direct Vent Applications)
2"
2"
2"
or
NOTE: 1-1/2" Vent Pipe
Diameter Allowed Only
on 045/070 Units
1-1/2"
or
TRANSITION
*2"
2.
If intake air is drawn from a ventilated crawl space
(Figure 26) or ventilated attic (Figure 25) the exhaust
vent length must not exceed those listed in Table 7C.
If 3" diameter pipe is used, reduce to 2" diameter pipe
to accommodate the debris screen.
3.
Use a sheet metal screw to secure the intake pipe to
the connector, if desired.
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
per 1.17kW) per hour of the total input rating of all equipment
in the enclosure.
Figure 25. Equipment in Confined Space
(Inlet Air from Ventilated Attic and Outlet Air to
Issue 2341
TOP VIEW
TRANSITION
*2"
3"
*2"
Ventilation Louvers
*Intake Debris
Screen
(Provided)
Furnace
* See Maximum Vent Lengths table
Outside)
INTAKE
EXHAUST
Inlet Air
(Minimum 12 in.
(305mm) above
Attic Floor)
2
Page 21 of 53
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