What is a Return Air Grille?

What is a Return Air Grille?

The return air grille is the ducted unit air intake grille that air from the building is sucked into the ducted system to the indoor fan unit before being conditioned and delivered back to the rooms as conditioned air.  Return air grilles in domestic installations normally have a filter installed.

Where would you find a return air grille? 

 Normal installation locations of return air grilles are:

  • In the ceiling – normally when the supply air outlets/vent are ceiling mounted
  • In the wall, this could be either high on the wall for ceiling mounted indoor units, or lower on the wall often when the indoor is installed either under the floor or in a plant room. 
  • Outlet vents, where the same linear grille could have both supply and return air duct fitted to the same vent. 
  • In some cases, there is no return air vents, but the return air filters are fitted directly to the back of the unit.

Return air filters, what are they and how often do they need to be cleaned? 

Return air filters are fitted to your ducted units to reduce/limit the amount of dirt or dust that is sucked on the indoor unit coil or fans. It is easier to clean a filter in a vent than it is to access and wash the coil of the unit. The key reasons that filters need to be checked and cleaned regularly:

  • Reduced dirt getting onto the coil and blocking up the coil which will reduce airflow and system performance
  • Reduce maintenance of your ducted unit
  • Reduces dirt getting into the drain which can often block up the drain and is a leading contributor to water leaking from the unit drains onto damage to walls or ceiling 
  • Blocked coils resulting in extra load onto the units and fans shortening the life of your system.

How often should the return air filters be cleaned? 

This is a great question, the answer is based on a few factors.  

  • How much do you use your system? 
  • How much dust is there in the building?
  • How big is your return air vent?
  • Is the vent installed at a high level or near the floor? If the vent is at a higher level versus lower level it affects the amount of dust is picked up by the system?

Filter timing for cleaning comes down to how much you use your system. Here is a guide to help you.

  • Limited use – its recommended that checking/cleaning the filter(s) every 6 months or the change of winter/summer seasons
  • Low use – Checking/cleaning of the filter(s) should be done every 4-5 months
  • Medium use – Checking/cleaning of the filter(s) approximately every 3-4 months
  • High use – Checking/ cleaning of the filter(s) 1-2months. 


Disclaimer – every installation is different and this is just a guide only. A rule of thumb is if the filters are still clean then its safe to increase the time between check/cleans or if they are dirty then decrease the time intervals.


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