How Ducted Air Conditioning Works: An Expert Guide

Ever wondered about the magic behind ducted air conditioning? You press a button on a central controller, and within minutes, your entire house is filled with refreshing, cool air, all without a single bulky unit on your walls. It’s a sophisticated and highly effective way to manage your home's climate, but the process behind it is a fascinating piece of engineering. Understanding how ducted air conditioning works can help you appreciate your system, use it more efficiently, and recognise when it needs expert attention.

The Indoor Fan Coil Unit
This is the operational core of your air conditioning system. It’s a large unit that is concealed in your roof cavity or underfloor space. This indoor unit houses the evaporator coil and a powerful fan responsible for treating and circulating the air.
The Outdoor Unit
Located outside your home, this unit contains the compressor, condenser coil, and a fan. Its primary job is to release the heat that has been extracted from your indoor air.
Ductwork
A network of insulated, flexible tubes that run from the indoor fan coil unit through your roof cavity to every designated room. These ducts are the highways for your conditioned air.
Vents and Grilles
These are the discreet outlets in your ceiling or floor where the cool air enters your living space. Your system also has a larger return air grille in a central location, which pulls indoor air back into the system to be re-cooled.
Thermostat and Controller
This is the user interface, usually a wall-mounted panel, that allows you to set your desired temperature, control zones, and manage your entire air conditioning.

Step 1: Capturing Warm Indoor Air
The cycle begins at the return air grille. The indoor fan coil unit actively draws warm air from your living spaces into the ductwork. This indoor air contains the unwanted heat that makes your home feel uncomfortable.
Step 2: The Heat Exchange at the Evaporator Coil
Once the warm air arrives at the concealed indoor unit, it is passed over a critical component: the evaporator coil. This part of the air conditioner is a network of pipes filled with a very cold liquid refrigerant.

As the warm indoor air blows across the cold evaporator coil, a heat exchange takes place. The heat energy naturally moves from the warmer substance (the air) to the colder one (the refrigerant). The refrigerant absorbs the heat, and in the process, the air becomes significantly cooler. This process also dehumidifies the air, which is crucial for comfort in Queensland.
Step 3: Distributing Cool, Conditioned Air
The fan inside the indoor fan coil unit then takes this newly chilled, conditioned air and pushes it through the extensive network of ducts. This cool air is distributed to the various rooms in your house, exiting through the vents to lower the temperature in your living space.
Step 4: The Refrigerant's Journey to the Outdoor Unit
After absorbing heat from your indoor air, the cooled refrigerant inside the evaporator coils has turned into a low-pressure, warm refrigerant gas. This gas is then pumped through copper pipes to the outdoor unit.
Step 5: Releasing Heat into the Outdoor Air
At the outdoor unit, the compressor works its magic. It pressurises the warm refrigerant gas, turning it into a very hot, high pressure gas. This hot gas then flows through another set of coils called the condenser coils. A large fan in the outdoor unit blows outside air across these coils.

This triggers another heat exchanger process. The heat from the refrigerant transfers to the cooler outdoor air and is dispersed. As the refrigerant loses its heat, it condenses back into a liquid state.
Step 6: The Cycle Begins Again
This now-cooler liquid refrigerant travels back towards the indoor unit. Before it enters the evaporator coil, it passes through an expansion valve, which causes it to become extremely cold again, ready to absorb more heat from your home. This entire cycle repeats continuously, keeping your home at the perfect temperature.

This efficient process is how all modern air conditioning systems work, but the scale and integration of a ducted air conditioning system make it perfect for whole-home comfort.

How does a ducted air conditioner work?
A ducted air conditioner works by using a central indoor unit hidden in the roof cavity to cool air. This cool air is then distributed throughout the entire house via a network of insulated ducts connected to vents in each room. The system works by absorbing heat from the indoor air via an evaporator coil and transferring that heat outside through an outdoor unit.
What are the disadvantages of ducted air conditioning?
The main disadvantages are the higher upfront cost compared to split system air conditioning and the complexity of the professional installation, which requires adequate space in the ceiling or under the floor. If not properly maintained, they can also be less energy-efficient and circulate poor quality air.
Do you need to open windows with ducted air conditioning?
No, you should always keep windows and doors closed when your ducted air conditioning is operating. The system is designed to recirculate and cool the air inside your home. Opening windows allows cool air to escape and warm air to enter, forcing your air conditioning system to work much harder and increasing running costs.
Does a ducted aircon take air from the outside?
Most standard ducted air conditioning systems do not; they recirculate the internal air. However, some ducted air conditioners have an optional fresh air intake that can be installed to draw in a percentage of fresh, oxygenated air from outside to improve ventilation.

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