Hitachi NES1-004SB Quick Reference Manual page 287

Chapter 13 Option
13.2.4 Reduction of the dust invades
・Because a top opening becomes the window shade construction as for the inverter of the NE-S1 series,
it is in the structure that direct, the dust from the top is hard to invade the products inside.
The dust from the top becomes hard to invade the inverter inside more by attaching optional FFM to an
applicable model.
The detail refers to figure 9
Figure9.FFM installation state
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