As summer heats up in New Zealand, homeowners rely heavily on their ducted air conditioning systems to keep their homes cool and comfortable. But what happens when your system isn’t performing as it should? If your ducted system is struggling to keep up with the rising temperatures, you’re not alone. Many homeowners experience performance issues that result in uncomfortable conditions during the day, and sleepless nights at night..
OneAir technicians have installed and serviced hundreds of ducted air conditioning systems for years and are often called to investigate why systems are not working to expectations. Whether it’s for residential or commercial use, we’ve helped provide solutions to homeowners and business owners alike with their ducted air conditioning problems. This guide taps into our years of experience and will walk you through common ducted air conditioning issues, their causes, solutions, and the benefits of proactive maintenance to keep your system running smoothly all summer long.
Common Problems with Ducted Air Conditioning Systems
1. Weak Airflow: Your Home Feels Warmer Than Usual
The Problem:
You’ve set the thermostat to a comfortable 22°C, but your home stubbornly stays around 24-26 °C . You hold your hand up to the vents to feel the airflow, and the air coming out feels weak, barely trickling out.
Possible Causes:
Dirty or clogged air filters restrict airflow
Blocked or leaking duct connections reducing air distribution
Poor duct design or
Faulty thermostat sensor giving incorrect readings
Low Blower fan speed affecting air circulation
Incorrect Static pressure setting hampering airflow
Solution:
Check and replace dirty air filters every 6-12 months (more frequently for high volume commercial properties).
Inspect ducts for leaks or blockages and if the ductwork is properly sealed against the vents.
Schedule a professional HVAC diagnosis to assess blower fan performance and measure airflow.
Benefits of Fixing This Issue:
Improved cooling
Lower energy bills
Better indoor air quality
Improved efficiency
2. Inconsistent Cooling: Some Rooms Are Too Hot, Others Too Cold
The Problem:
One room feels like an icebox, while another feels like a sauna, making it impossible to stay comfortable throughout your home.
Possible Causes:
Poor air balancing with too much conditioned air entering one room and insufficient amounts entering others
Kinked or squashed ducts causing pressure drops and weak airflow
Gaps in connections to vents causing conditioned air to be wasted
Solution:
Ensure thermostat placement is in a central location and not exposed to direct sunlight.
Have an HVAC professional inspect and seal ducts before undertaking air balancing.
Keep vents open and the duct runs straight and unobstructed.
Benefits of Fixing This Issue:
Even temperature distribution
Reduced energy consumption
Enhanced comfort in every room
3. Unusual Noises: Your System Sounds Like a Jet Engine
The Problem:
Your ducted air conditioning system is too noisy with loud whistling from the return grilles, or starts making unsettling weird noises—banging, whistling, or rattling—that weren’t there before.
Possible Causes:
Loose or damaged components such as bearings, fan blades or motor parts
Duct leaks causing high-pitched whistling sounds
Return grilles blocked or too small for system
Debris buildup inside the system
Solution:
Tighten any loose screws or fittings.
Have a technician inspect and repair duct leaks as well as perform an assessment to see if additional or larger return grilles are needed
Clean out debris from the system.
Benefits of Fixing This Issue:
A quieter, more peaceful home with air conditioning so quiet, you hardly know it is even turned on
Prevention of further damage to system components
Improved efficiency and performance
4. Higher-Than-Normal Energy Bills
The Problem:
Your power bill has skyrocketed for some unknown reason, even though your cooling habits haven’t changed.
Possible Causes (air conditioning-related only):
Dirty coils or filters forcing the system to work harder
Duct leaks causing cooled air loss and you compensate by increasing the fan speed and/or lowering the temperature
Aging or failing components reducing efficiency
Solution:
Clean or replace air filters regularly.
Have a professional inspect and seal duct leaks.
Consider upgrading to a more energy-efficient model if your system is over 10 years old.
Benefits of Fixing This Issue:
Significant savings on energy bills
Reduced strain on the HVAC system and increased system lifespan
5. Unpleasant Odours: Your Home Smells Musty or Burnt
The Problem:
Every time your air conditioner turns on, you notice a musty, burning, or foul smell spreading through your home.
Possible Causes:
Mould or mildew growth in ducts due to moisture buildup
Overheated components releasing burning smells
Dead birds or rodents decomposing inside ductwork
Solution:
Have ducts cleaned professionally or replaced with new ones
Ensure proper ventilation and humidity control.
Schedule professional HVAC maintenance to check electrical components and remove debris.
Benefits of Fixing This Issue:
Healthier indoor air quality
Elimination of unpleasant odors
6. System Shutting Down Intermittently
The Problem:
Your ducted system keeps turning off before reaching the desired temperature, leaving your home uncomfortably warm.
Possible Causes:
Thermostat malfunction misreading temperatures
Overheating system due to dirty filters or clogged coils
Low refrigerant levels icing the coils and causing premature shutdown
Solution:
Reset or recalibrate your thermostat.
Clean filters and condenser coils.
Have an HVAC professional check refrigerant levels.
Benefits of Fixing This Issue:
Consistent cooling without interruptions
Prevention of system overwork and breakdowns
Longer lifespan of your AC unit
7. Excess Humidity Inside Your Home
The Problem:
Even with the AC running, your home feels sticky and humid, making it uncomfortable.
Possible Causes:
Low refrigerant gas levels
Improperly sized system unable to remove excess moisture
Dirty evaporator coils reducing dehumidification efficiency
Clogged condensate drain causing moisture buildup
Solution:
Ensure your ducted system is properly sized for your home.
Clean evaporator coils and unclog condensate drains.
Consider adding a dehumidifier for extra moisture control.
Benefits of Fixing This Issue:
Enhanced comfort levels
Prevention of mold growth
Improved indoor air quality
Preventative Maintenance: The Key to a Problem-Free Summer
If your home feels uncomfortably warm, if strange noises or odours are coming from your vents, or if your energy bills have inexplicably spiked, don’t wait for things to get worse. A professional HVAC inspection can help you catch problems early, ensuring your system works efficiently when you need it most.
Many of the issues listed above can be prevented with regular maintenance. Here’s why servicing your ducted system is essential:
Extends the lifespan of your unit by preventing wear and tear.
Improves energy efficiency by ensuring optimal performance.
Enhances air quality by keeping filters and coils clean.
Reduces costly repairs by catching issues early.
How Often Should You Service Your Ducted System?
HVAC professionals recommend servicing your ducted air conditioning system at least once a year, preferably before summer begins. This ensures your system is ready to handle peak performance demands.
Ready to Fix Your Ducted Air Conditioning System Problems? We Can Help!
Don’t let an underperforming ducted system ruin your summer comfort. If you’re experiencing any of the issues above, schedule a professional inspection today. Our expert technicians will diagnose the problem, provide tailored solutions, and restore comfort to your home interior. Contact us today for a professional HVAC expert callout!