Innova IGZDUP35V2NI-1 Owner's Manual page 37

(2) If the downward return air method is adopted, then install the return air
cover at the back of the unit after dismantling it.
(3) Connect the return duct to the return air inlet of indoor unit with rivet, and
the other side shall be connected to the return air inlet. For the
convenience of free height adjustment, canvas duct can be made and
reinforced with iron wire to a folding shape.
(4) The noise of downward return air is obvious bigger than that of rear return
air. For downward return air, silencer and static pressure carton shall be
added to conduct noise reduction treatment.
2.2.7.3 Installation of Supply Air Duct and Return Air Duct
Installation method shall be selected by entirely considering the conditions of
buildings, maintenance, etc.as is shown in the following figure.
NOTE:
The return air pipe must be connected to the air duct, and the internal
components cannot be touched by hands after installation. During installation and
maintenance of the unit, the disassembly must be done by the professionals.
2.2.7.4 Installation of Fresh Air Duct
(1) While connecting the fresh air duct, cut off the fresh air baffle plate as is
shown in the following figure. If the fresh air duct is not used, block the
gap of fresh air baffle plate with sponge.
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