The air return filter on a ducted air conditioning system requires regular cleaning.
Dust collects on the filter and restricts the airflow. The restricted airflow reduces the efficiency of the system and if it becomes blocked it can cause damage to the fan coil unit.
In a normal residential house the filter should be checked/cleaned every six months. On the Daikin ducted systems a filter message comes up on the controller. This message is time based and not related to the amount of dust/dirt on the filter. It will prompt you to clean the filter.
The steps for cleaning a ducted return air filter are (no tools are needed):
Undo the hinged Return Air Grill frame fixing(s).The fixing(s) is usually a thumb screw or a sliding clip.
Swing the filter frame open and let it hang vertically.
Slide out the filter.
Clean the filter by washing in warm water
Place the filter in the sun to fully dry out.
Slide the filter back into the hinged grill, swing the grill back into the recess and screw up the fixing screw(slide back the clip).
Before & After
The filter on the right before cleaning is covered in dust.