Downflow Duct Connectors; Residential And Modular Home Upflow Return Plenum Connection; Side Return Application; Bottom Return And Attic Installations - Johnson Controls RL18 Installation Manual

Figure 7: XAH horizontal right application with furnace
Figure 8: XAH horizontal left application with furnace

Downflow duct connectors

All downflow installations must use a suitable duct
connector approved by the furnace manufacturer for
use with this furnace. The duct connectors are designed
to connect to the rectangular duct under the floor and
sealed. Refer to the instructions supplied with the duct
connector for correct installation.
Residential and modular home upflow
return plenum connection
Return air may enter the furnace through the sides or
bottom depending on the type of application. Do not
connect return air into the rear panel of the unit.
Installation Manual: RL18 Single-Stage Standard ECM Residential Gas Furnaces (Non-condensing Multi-position Standard

Side return application

Side return applications pull return air through an
opening cut in the side of the furnace casing. The furnace
is supplied with a bottom blockoff panel that must be
left in place if using a side return. If installing the furnace
on a flat, solid surface, this bottom panel provides an
adequate seal to prevent air leakage through the unused
bottom opening. However, if installing the furnace on
a surface that is uneven or if installing on blocks or
otherwise raised off the floor, it is necessary to seal the
edges of the bottom panel to the casing using tape or
other appropriate gasket material to prevent air leakage.

Bottom return and attic installations

Bottom return applications normally pull return air
through a base platform or return air plenum. Ensure the
return platform structure or return air plenum is suitable
to support the weight of the furnace. The internal bottom
panel must be removed for this application.
Attic installations must meet all minimum clearances to
combustibles and have floor support with the required
service accessibility.

Downflow application

For downflow applications, turn the furnace upside down
so the circulating air enters the furnace at the top and
exits the furnace at the bottom. Rotate the combustion
air inducer 90° as shown in Figure 24. Do not block the
combustion air inlet openings.

Horizontal application

Figure 9: Horizontal application
Important: It is possible to install this furnace in a
horizontal position on either side as shown above.
Do not install this furnace on its back.

Attic installation

Figure 10: Typical attic installation
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Low NOx)