A ducted system is one of the biggest mechanical investments in your home. Look after it and you’ll get 15 to 20 years out of it. Neglect it and you’re looking at premature compressor failure, climbing power bills, and a replacement quote you didn’t budget for.

The good news is that the maintenance routine isn’t complicated. Most of it is homeowner-level work. The rest is an annual visit from a licensed technician. Here’s how we walk our Sydney clients through it.

What you can do yourself

Three jobs cover the bulk of homeowner maintenance. None of them need tools or technical knowledge.

Clean the return air filter

If you do nothing else, do this. The return air filter is the single biggest factor in how well a ducted system runs. When it clogs, airflow drops, the system works harder to hit the set temperature, your bills climb, and the dust the filter is meant to catch starts circulating through the house instead.

Check it monthly. Clean or replace it every one to three months, more often if you’ve got pets, anyone smoking in the house, or the system is running heavily through summer. The filter usually sits behind the return air grille on a hallway ceiling or wall, and slides out without tools. Vacuum the worst of it, rinse under the tap if it’s a washable type, let it dry completely, and slot it back in.

We see plenty of Western Sydney homes where the filter hasn’t been touched since installation. By year three it’s not a filter, it’s a felt mat. Ten minutes a month avoids that.

Keep the supply vents clear

Walk through each room and check the ceiling vents aren’t blocked by furniture, stored boxes, tall curtains or wardrobes pushed up under them. Wipe dust off the grilles every few months. A ducted system is balanced to push a specific amount of air through every outlet in every zone, and choking one of them off changes how the rest of the system behaves.

Clear around the outdoor unit

The condenser unit needs roughly a metre of clearance to breathe. Pull out fallen leaves, trim back any plants that have grown into it, brush off cobwebs and built-up dirt around the fins. Once a year, switch the system off at the isolator and gently hose down the outside of the unit. In leafy parts of Sydney like Hornsby, the upper North Shore, and the Hills district, this matters more than people realise. Leaf litter against a condenser in February will cook a unit before its time.

What needs a licensed technician

Anything past those three jobs is licensed work. The reason isn’t paperwork. It’s that the refrigerant circuit, the electrical components, and the ductwork all sit in places you can’t safely or legally get to without the right qualifications. Refrigerant work in particular is restricted to ARC-licensed technicians under federal law.

A standard ducted service should cover the following.

Coil cleaning. Both the indoor evaporator coil and the outdoor condenser coil pick up grime over a season. Dirty coils kill heat transfer, which means the system runs longer to do the same job and your power bill reflects it.

Refrigerant pressure check. Low refrigerant is the single most common reason a ducted system loses performance over time. We check operating pressures and look for the leak. Topping up without finding the leak is throwing money at the problem and usually means a bigger repair within a year.

Electrical safety check. Capacitors, contactors, isolators and control wiring all get inspected. These are the components most likely to fail without warning and leave you without cooling on a 38°C day. The work falls under AS/NZS 3000.

Ductwork inspection. Damaged, disconnected or poorly sealed ducts can lose 20 to 30 percent of your conditioned air into the ceiling cavity. You’re paying to cool the roof space. We pressure-check accessible runs and inspect the joins, plenum and flexible duct for damage.

Zone motor and thermostat test. If your system is zoned, each zone motor needs to open and close properly on demand. We cycle through every zone, check the dampers, and recalibrate the thermostat if it’s reading off the actual room temperature.

Drain line clear. The condensate drain runs with algae, dust and biofilm over time. A blocked drain backs water up into the ceiling, and a flooded ceiling is a five-figure repair on top of the aircon work. Clearing the line takes ten minutes during a service.

“The jobs that come back to bite people are almost always the ones nobody looked at. A blocked drain line that floods a ceiling. Low refrigerant that wears out a compressor. A leaky duct dumping cold air into the roof space for three years. None of these are dramatic on day one, but they’re the difference between a system lasting 10 years or 20.”

Helal, Crown Air

How often to book a service

For most Sydney homes, once a year is the right cadence. The best window is autumn, before you switch the system to heat for the cold months, or early spring, before the first proper heatwave hits.

Twice a year isn’t overkill if any of the following apply: the system runs more than eight hours a day, you’ve got multiple pets, you’re in a dustier pocket of Sydney (the Liverpool corridor, Penrith, parts of Western Sydney generally), or you’re inland enough to cop the worst of summer dust and bushfire smoke. After the 2019-20 bushfire season we pulled return filters across the basin that looked like they’d been run through a sandpit.

Manufacturer warranties also tend to require evidence of regular professional servicing. If you ever need to make a warranty claim on a compressor or PCB, the first thing the manufacturer asks for is service records. No records, no claim.

What it costs versus what you save

An annual ducted service typically runs $200 to $400 depending on system size and access. A new ducted system replacement is $8,000 to $20,000 or more depending on the home. The maths isn’t complicated.

Beyond avoiding early replacement, a properly maintained ducted system runs at roughly 15 to 20 percent higher efficiency than a neglected one. On a Sydney home running ducted heating and cooling for half the year, that’s a few hundred dollars a year in power bills, every year.

Book before the season hits

Every year we get the same calls in late November and early December. Someone’s flicked the system on for the first hot day, it’s not cooling properly, and by that point every aircon company in Sydney is booked solid for repairs. The first heatwave of the season is the worst possible time to discover your system needs work.

Get ahead of it. Book your ducted service in autumn or early spring, while technicians have actual capacity in the diary.

Frequently asked questions

How long should a ducted air conditioning system last? With proper maintenance, 15 to 20 years on the major components is realistic. Without maintenance, 8 to 12 years is more typical, often with a major repair somewhere in the middle.

Can I service my own ducted system? You can clean filters, clear vents and tidy around the outdoor unit. Anything involving the refrigerant circuit, electrical components or accessing the indoor unit needs a licensed technician. Refrigerant work specifically requires an ARC licence.

How long does a ducted service take? Most ducted services run 60 to 90 minutes for a standard residential system. Larger homes with multiple zones or harder roof access can push out to two hours.

Why is my ducted system not cooling some rooms properly? Common causes are a clogged return filter, blocked supply vents, a zone motor stuck closed, low refrigerant, or duct damage in the roof space. The first two are homeowner fixes. The rest need a technician on site.