Trane Oxbox J4HP4018A1 Installation Instructions Manual page 5

When the unit is installed in a hot and humid place, If the humidity
inside the installation space might exceed 86℉ and RH 80%, it is
recommended to insulate the cabinet exterior.
Use glass wool or polyethylene foam as insulation so that the
thickness is more than 2 in. and fits inside the installation space
opening.
Respectively, condensation may form on the surface of the insulation.
Be sure to use insulation that is designed for use with HVAC Systems
Condensation may form on the product during cool operation. It is
also recommended to use second drain pan and secure the unit firmly
to prevent it from falling.see Fig.4 and Fig.5 .
Drain piping
Second drain pan
Fig.5 INSTALLED HORIZONTALLY
Second drain pan
Drain piping
Fig.4 INSTALLED VERTICALLY
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