Ducted reverse-cycle air conditioning buying guide

Want to cool and heat your whole house? Here's what you need to consider.
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03.Selecting a system

The size and design of a ducted cooling and/or heating system depend on a range of factors:

  • Your home’s floor plan: How many levels are there? What are the dimensions of the rooms (including ceiling height)? Which direction do the rooms face?
  • The size, position and orientation of windows and doors.
  • The type of construction (for example, weatherboard or full brick).
  • The level of insulation.
  • The number of people living in your home.
  • The main use of the area (for example, sleeping, living, cooking).
  • The ceiling cavity space - slimline systems are available for homes with small ceiling spaces.
  • Outdoor spaces - just as with split system air conditioners, the outdoor compressor unit(s) needs to be installed somewhere where noise won't be an issue (for you or your neighbours).
  • Large systems may require a three-phase power supply, which will be an extra installation cost if you don't already have it.

That’s why you shouldn’t buy such a system "off-the-shelf" — get the supplier to design it for your individual situation.


There are several design features to consider. A supplier may be able to offer a range of options, depending on the design and requirements of your home.

  • Vents come a variety of designs and can be installed in the ceiling or walls.
  • Controls are usually hard-wired and mounted on a wall, unlike the remote controls used for single split-systems. You may have one controller for the entire system, but in a large house you might opt for extra controllers in other parts of the house for more convenience.
  • Sensors are used by the controller to keep the room at the targeted temperature. Large open-plan areas may need multiple sensors.
  • Zones: most systems allow for a home to be divided into zones for convenience and economy, so that you can turn on the air conditioner for only the part of the house you want cooled/heated (say, living areas, bedrooms, or different floors) rather than the whole house. Or, you can set different climate levels for different areas as required.


The ducting is a key component of the system. Ducts need to be thermally efficient so that valuable cooling or heating isn't lost between the air conditioner unit and the target room. The ducting industry association, ADMA, is concerned that some suppliers are installing inferior ducting, and recommends that consumers check with their installer that the ducting meets the Australian standard for ductwork, AS 4254. A new draft version of this standard calls for ducting to be labelled with the manufacturer name and the thermal value of the insulation, to help ensure the correct ducts are used.  Check the labels on the ducts or get a written statement of compliance to make sure you get the right quality of ducting.

Cooling capacity

The calculator below is for determining the required cooling/heating capacity for a single room: use this for each room to be air-conditioned, as a guide to the overall cooling capacity your what you need.


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