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Supply Air Diffuser Sizing and Location

Supply Air Diffuser Sizing and Location

The process of distributing heated or cooled air throughout your home should be a seamless process. The right aircon diffuser will ensure optimum airflow performance.

What is an aircon diffuser?


Essentially, an air con diffuser directs and controls airflow in an air conditioner. Air conditioner diffusers are a critical component in a heating, ventilation or air conditioning unit. In ducted air conditioning, the diffuser delivers air to each zoned area.

Air con diffusers can be purchased in a variety of shapes, including square, circular or rectangular. They can be constructed of plastic, aluminium, metal, stainless, timber or cast iron. Diffusers also come in a number of configurations, such as swirl diffusers and slot diffusers.

Are an air con diffuser and an air conditioning linear slot diffuser the same?

Yes. A linear slot diffuser is a superior, modern and flexible type of air con diffuser that features a long, narrow design. It can be used to direct air in multiple directions. This special shape makes it easy for builders to fit the air con diffuser into a tight space and helps to conceal the diffuser from view for a more aesthetically pleasing design.

Air conditioner diffuser sizing

The size of the aircon diffuser is the diameter of the neck to which the flexible duct is connected. The air con diffuser sizing is determined by:

Area                       Ceiling Height         Diffuser size(dia.)
Up to 12 sqm          2.4 – 2.7m                200mm
Up to 12 sqm          3m                            250mm
Up to 20 sqm          2.4m – 2.7m             250mm
Up to 20 sqm          3m                            300mm
Over 20 sqm                                           multiple diffusers

For example, an average-sized bedroom is approximately 3 metres x 3 metres. For this size of room, we recommend a 200mm round diffuser.

Diffuser layout

Aircon diffusers for small rooms

Bedroom: Position the air con diffuser at the end of the bed
Study: Position the air conditioner diffuser in the centre
Ensuite: Position the air con diffuser in the centre but away a source of steam, such as the shower

The ceiling is the most preferred place to install diffusers with a horizontal airflow.

Large rooms/areas

A round air con diffuser will spread cool air approximately 3 metres. If the room is longer than 5 metres, we recommend using multiple diffusers, spaced up to 6 metres apart and up to 3 metres from the wall.

Ducted air conditioning will feel softer when the air is coming from many directions. Therefore, 2 smaller diffusers will provide softer air conditioning than 1 large diffuser. For example, a living room 6 metres long x 4 metres wide with a 2.7 metres ceiling.

Locate one 200 millimetre diffusers, 2 metres from the longer wall and 2 metres from the shorter wall. Locate a second 200 millimetre diffuser, 2 metres from the wall at the other end of the room.

Practical considerations limiting the ideal location of aircon diffusers

  1. Lights, ceiling roses, skylights, ceiling fans
  2. Beams and ceiling joists
  3. Insufficient roof space

The final layout will be decided by the installer and the client.

An experienced air conditioning diffuser supplier can provide you with a suitable air diffuser to suit your requirements. To ask us a question about aircon diffusers, contact Crown Power today on 0427 175 654 (Brisbane & Sunshine Coast) or 0421 376 620 (Gold Coast).