Which is the best ducted air conditioning system?

Which is the best ducted air conditioning system?



You're interested in heating, cooling and dehumidifying your home with the incredible efficiency of heat pump technology. You've decided that reverse-cycle ducted air conditioning is the tool for the job...but which product should you choose? 
Not sure if a ducted air conditioning system is the way to go? Head to our article, 'How can I replace my gas heating system?'
In this article, we will save you time by providing an overview of the technology and some considerations, before recommending some good options. Then we'll finish up by giving you some pointers to assist your planning with an installer.

A quick summary of heat pump technology  

Heat pumps are a familiar technology; you have one in your fridge! They extract thermal energy from the ambient air and use it to provide cooled (or heated) air. 
 
But unlike a refrigerator, an air conditioning heat pump system has separate indoor and outdoor units. They are also capable of heating as well as cooling, which is why you'll often hear them described as, "reverse-cycle".
 
The brilliance of this process is that heat pumps can extract about 3 units of heat energy from the air for every unit of energy put in from electricity!
 
This makes the running costs for a heat pump very low compared to other technologies.

A quick summary of ducted systems

Once a central heat pump has raised or lowered the air temperature, ducted systems use a series of ducts to circulate the warmer or cooler air through a home or building.
 
The central fan-coil unit is normally housed in the roof or floor space and ducts are hidden from sight, with air entering rooms through small vents. Return air intakes will also be installed in each room as well as the vents, to circulate air back to the central unit.

General considerations

You can't reuse gas heating ducting  

If you're here because you've got gas ducted heating and you're hoping to save time and money by plugging a reverse-cycle air conditioner into the existing duct work, we've got some bad news.
 
One of the best things about reverse cycle air conditioning is the ability for the system to cool, heat and dehumidify air.
 
Unfortunately, in order to do this with any effectiveness the system needed specific ducting.
 
If you've got ducts for heating only in your ceiling, they won't be able to handle both heating and cooling. You'll need to replace all your ducting.
 
Similarly, if you've already got a zoned heating system, you'll need to replace the zoning controllers as they won't be compatible with your new system.
 
In summary, you'll need to get everything stripped out and replaced if you're switching to an electric solution.
 
In good news, at least you know you've got space for ducting and zoning controllers.
If you're having second thoughts about a ducted system, head over to our article on split system air conditioning to consider more cost-effective and efficient options.

You'll need a specialist to design your system

Ducted systems use a central unit to heat or cool the entire home. This means they are complex and require a trained professional to design. 
Even though it's not something you should try to take on, you can still make sure your designer is doing a good job! We'll address the things your designer should be covering later in the article.

Ducted systems are expensive 

Whichever way you look at it, ducted reverse cycle air conditioning is not a cheap option.
 
As a ball-park, a 15kW system with two zones and eight vent points will cost around $14,000 to install, not factoring for electrical upgrades.
 
Every extra zone will cost about $300 to add, and each vent point an additional $400.
 
Also consider that for larger homes the cost of ducting and pipework will start to add up quickly.
For existing properties with multiple floors, you may need to install a separate ducted system for each floor.

Installers  

It's worth remembering that installers will be the ones to honour guarantees if something goes wrong. Make sure your installer is established with a strong track record.
 
We put all our tradies through checks to make sure they are reliable.
 
Also, make sure you get licensed tradespeople to complete the work so the install is to accreditation standards, and they are able to issue a compliance certificate.
 
Depending on your requirements, the replacement may involve electrical and plumbing work and so looking for a provider that can do both will save you time and potentially money.
We'll share things to think about for installation and the process to filter for good tradies at the bottom of this article.

Design considerations 

As mentioned, designing a ducted system is best left to the professionals. However, there are some things you can get straight that will help a professional propose the best system for your requirements.

Electrical requirements   

Always start with your electrics! Single-phase power is all you need for most single (and multi) split-system air conditioners. However, ducted systems use a large central unit that will draw more current.
 
Depending on the requirements of your system you'll potentially need to upgrade your mains supply, either increasing your single-phase mains supply or even upgrading to three-phase if you've got a large, multi-storey house.
 
In addition, the ducted system will require a dedicated circuit, so you may need to create additional space on your switchboard if it is already full. Check your switchboard and factor in the cost of any necessary upgrades to add space for more circuits.
 
This can add considerable cost to your project, so be prepared for this to be part of an installation quote.
If this talk about 32A and 63A and phases is confusing, head to our article, 'Will I need to upgrade my power?'

Zoning 

Most ducted 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 or heated.
 
For example, living areas during the day and bedrooms after 10pm, or different floors, rather than the whole house. Or, you can set different climate levels for different areas as required.
 
The benefits of zoning is that it will significantly reduce your running costs, as it will avoid the waste of unoccupied climate controlling rooms.
 
The disadvantage is that every added zone will increase the installation cost.
Consider how everyone at home occupies the space; are there typically rooms that are always used at the same time? What's the best balance of grouping rooms but not requiring too many zones?

Ceiling or underfloor space 

You'll need space for the central unit and ductwork for conditioned and returning air. This shouldn't be too much of a problem if you're replacing the hardware for a gas ducted heating system.
 
If there's limited ceiling space, you might need underfloor ducts instead, though slimline systems are available for homes with small ceiling spaces.
 
If you don't have space, consider split system air conditioners.

Outdoor unit placement 

While noise should not be a concern with the compressor. If you or your neighbours are sensitive, just as with split system air conditioners, there are considerations that you can make:
  1. Installing the compressor unit as far from the border of a neighbouring property as possible;
  2. If installed windward side, an acoustic screen should be used;
  3. Construction materials in near proximity such as fencing, other buildings, etc. can absorb noise;
  4. Decentralising the placement of units if you have several heat pumps being used1.

Which one should you buy?  

Here's the thing; there's not a huge difference between the major air conditioning brands. Most of them provide a 5 year warranty and use the same refrigerants (if you're worried about environmental impact), and have a lot of comparable system control features.
 
Instead of starting with a particular brand, focus more on choosing a good installer who proposes a design based on your requirements that balances up-front cost and ongoing running costs.
 
If an installer proposes any of the following brands as part of their system, you'll be fine:
  1. Mitsubishi Heavy Industries
  2. Daiken
  3. Mitsubishi Electric
  4. Fujitsu General
  5. Toshiba
As mentioned, the whole-home design of a ducted system is more critical than a specific brand or product. If want to work with Energy Freedom Homes, we'll help
 you find the sweet spot of sizing a system and zoning and vent placement to heat, cool and dehumidify your home as cost effectively as possible. Get started by checking your readiness for one of our Home Electrification Masterclasses!

Installation tips  

Hopefully, by now you're clear on the range of products that will heat and cool your home. As you start thinking about your installation and speaking to tradies, here are a couple of tips to make sure you get the most out of your split systems.

Things your installer should be asking about 

To design the best system for your home, your designer should be checking the following things to size the central unit, locate vents and add any zoning:
  1. 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?
  2. The size, position and orientation of windows and doors.
  3. The type of construction (for example, weatherboard or brick veneer).
  4. The amount of insulation in the ceiling, under the floor and in the walls.
  5. The number of people living in your home.
  6. The main use of each area (for example, sleeping, living, cooking).

Design decisions 

Expect to work through the following things with your designer.

Vents  

Which style of vent? This should be based on:
  1. Preference or practicality;
  2. Placement on the wall or ceiling.

Controls 

These are usually hard-wired and mounted on a wall, unlike the remote controls used for single split-systems. You might be asked to choose between a single controller for the entire system, or extra controllers in other parts of the house. 

Ducting 

This is obviously a critical part of the system! You want to make sure your ducts are thermally efficient so that valuable cooling or heating isn't lost travelling 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 42542.
 
Check the labels on the ducts or get a written statement of compliance to make sure you get the right quality of ducting.

Warranties  

How long are you covered by a guarantee with a certain product?
 
This can massively reduce the financial risk you are taking on by investing in a new system. Treat warranty periods as one of your most important decision-making factors.
 
Most established brands from budget to high-end offer a 5 year warranty. Make sure the product you are considering will at least match this industry standard.
Check what components or labour the guarantee covers. Some unit components may have a longer warranty period than others. This should be clearly outlined in the warranty terms on the manufacturer's website.

Ceiling fans 

If you've got a ceiling fan that has a reverse mode, you'll be able to slash heating costs by running it at the same time as your air conditioning.
 
This is because it pulls the hot air down from the ceiling and circulates it around the room more effectively, requiring less time and power to reach a uniform and comfortable temperature.
Doesn't running two things end up costing more? No, because the ducted system (which is more expensive to run) won't have to work as hard for the same result. Fans are very energy efficient when compared to split systems3.
If you don't have a ceiling fan installed, consider getting your tradie to put one in when they install your split system.

Checks for your installers  

You'll need a licensed air conditioner installer because of the gas refrigerant. Look for an installer with ARCtick approval.

As well as an ARCtick accreditation, your air conditioner installer should have an electrical qualification in order to wire your air conditioner into your home and issue a certificate of compliance after the work is done. Many don't, but this means they'll be unable to offer a warranty on the electrical work, only the air conditioner itself.

Likewise, plumbing your air conditioner's drain into your home's stormwater system needs to be performed by a qualified plumber. Check that the installer you choose has the necessary accreditations to carry out the whole installation.

Next steps

Hopefully you're ready to co-design the best ducted system setup for your home.
 
Ready to get started? Make sure you have the right supplier to get the job done. We have some advice in our 'How to find a trusted tradie' article...
 
...or get in touch and we can connect you with one of our trusted tradies. Join an Energy Freedom Homes Masterclass and learn to identify your needs, gain expert installation advice, and meet trustworthy tradespeople. Check your Masterclass readiness now!
 
If you are all set with your planning for heating upgrades, take a moment to congratulate yourself! When you are ready to move to the next area of upgrades in your journey to an Energy Freedom Home, such as cooking or hot water, click here to head to our planning article.
The recommendations in this article come from talking with real people and communities to identify a best-fit option for a range of priorities. We also do our research; each of the above recommendations is based on ratings from Choice Magazine, Canstar, ProductReview and general consensus from the popular Facebook group, My Efficient Electric Home.

References

1 Flimel, M. (2018). Potential optimisation of heat pump placement in terms of environmental noise levels. Chapter 5 pp. 153-174. In, Tea Espenson. (ed.). Heat Pumps: Performance and Applications. Nova.
2 ADMA: Australian Duct Manufacturers Alliance. (n.d.). Welcome to ADMA. Retrieved  2023, from  http://adma.net.au
3 Davies, L. L. (2022). Ceiling fans vs air conditioning: pros & cons. Canstar. Retrieved  2023, from  https://www.canstarblue.com.au/appliances/ceiling-fans-or-air-conditioning-the-pros-and-cons/