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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.
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 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 7D for pipe sizes.
Follow the next 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 24. 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.
2.
If intake air is drawn from a ventilated attic (Figure
25) or ventilated crawlspace (Figure 26) the exhaust
vent length must not exceed those listed in Table
8A through Table 8B. 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.
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 exhaust air as well as the maximum volume of
combustion air required for all gas appliances serviced
by this space.
507769-05G / 31-5000656
CAUTION
NOTE: Debris screen and elbow may be rotated so that the
screen may be positioned to face forward or to either side.
Figure 24. Typical Air Intake Pipe Connections
Non-Direct Vent Applications
Roof Terminated
Exhaust Pipe
* See Maximum Vent Lengths table
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 2223
Intake
Debris
Screen
(Provided)
Ventilation Louvers
Inlet Air
(Minimum 12 in.
(305mm) above
Attic Floor)
*Intake Debris
Screen
(Provided)
Furnace
Outside)
Page 21 of 55
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