Air handling units (AHUs) are key to comfortable, healthy indoor environments, particularly in Perth and Western Australia’s diverse climate. However, from time to time, they can face various performance issues. It’s important to understand and address these problems to maintain your AHU’s longevity and efficiency. This article dives into common AHU issues and offers detailed troubleshooting tips to help you keep your unit running smoothly. 

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Understanding air handling units 

An AHU is a key component of a building’s HVAC system, designed to condition and circulate air. It typically includes a blower, heating or cooling elements, filter racks, sound attenuators, and dampers, all housed within a metal box. Connected to a network of ducts, it distributes conditioned air throughout the building. 

Common issues with air handling units 

Air handling units (AHUs) are crucial for creating comfy indoor spaces in Perth and WA’s varied climate, but they can run into some issues. Here’s a rundown of common issues that might pop up and how to tackle them. 

Inadequate airflow 

Inadequate airflow in AHUs is a prevalent issue that impacts indoor comfort and leads to higher energy usage. This problem can arise from several factors, including clogged filters, issues with the fan, blockages in the ductwork, or malfunctioning dampers. Addressing these issues effectively can enhance the performance of your AHU. 

Troubleshooting tips 

Regular inspection and replacement of air filters: 

  • Check air filters every three months and replace them if they are clogged with dust and pollen, as this can restrict airflow. 
  • Ensure the new filter is correctly sized and compatible with your unit. 

Examination of fan blades and motor: 

  • Inspect fan blades for any signs of damage or misalignment, which can impact airflow efficiency. 
  • Regularly check the fan motor for wear or unusual sounds. Routine maintenance like lubrication and belt tension adjustment can prevent problems. 

Clearing ducts of obstructions: 

  • Conduct visual inspections of your ductwork to identify any blockages or disconnections. 
  • Remove visible debris and consider a professional cleaning for inaccessible areas. 
  • Seal any leaks in the ductwork to prevent loss of air. 

Checking and adjusting dampers: 

  • Ensure dampers are correctly positioned and functioning, as they control the flow of air through the ducts. 
  • Make adjustments as needed to ensure even airflow distribution throughout your space. 

Strange noises 

Unusual sounds like rattling or buzzing from air handling units (AHUs) are common concerns. These sounds typically indicate mechanical issues that, if addressed promptly, can prevent more serious problems. 

Troubleshooting tips 

Tightening screws and fasteners: 

  • Rattling noises often come from loose components within the AHU. 
  • A thorough check and tightening of all screws and fasteners can eliminate these noises. 

Checking fan and motor alignment and balance: 

  • Buzzing or humming sounds can be due to misalignment or imbalance in the fan or motor. 
  • Inspect and adjust the fan blades and motor alignment to ensure smooth operation. 
  • Balancing the fan can also help reduce these types of noises. 

Removing debris and obstructions: 

  • Sometimes, debris caught in the AHU can cause unusual sounds. 
  • Investigate the interior of the unit for any foreign objects or buildup and carefully remove them. 


Overheating in AHUs is a notable issue, especially in the climate of Perth and Western Australia. It can lead to system failures and is often a result of inadequate maintenance or ventilation problems. Addressing this effectively is crucial to prevent system breakdowns. 

Troubleshooting tips 

Regular cleaning of the AHU: 

  • Dust and debris accumulation in the AHU can restrict airflow, leading to overheating. 
  • Scheduled cleaning of the unit, including the filters and internal components, is vital to prevent this. 

Ensuring adequate ventilation around the unit: 

  • Proper ventilation is essential for heat dissipation from the AHU. 
  • Ensure that the unit is not obstructed by furniture or other items and that there’s sufficient space around it for air circulation. 

Regular inspection of the motor and electrical connections: 

  • The motor and electrical components are prone to wear and tear, which can contribute to overheating. 
  • Regular checks for signs of damage or wear can identify issues before they lead to overheating. 

Thermostat issues 

Thermostat problems can significantly impact the operation of AHUs, leading to inefficient temperature control. Particularly in the summer months, you might feel like you’re working in a sauna instead of your office! 

Troubleshooting tips 

Regular checks and recalibration of the thermostat: 

  • Inaccuracies in the thermostat can lead to improper functioning of the AHU. 
  • Regularly test the thermostat for accuracy and recalibrate it if necessary to ensure it reflects the actual temperature accurately. 

Ensuring proper connection and configuration: 

  • Incorrect connections or settings on the thermostat can disrupt AHU operation. 
  • Check that the thermostat is properly connected to the AHU and that all settings, including temperature ranges and schedules, are correctly configured. 

Considering thermostat replacement: 

  • If thermostat issues persist despite troubleshooting, it may be time to replace it. 
  • Upgrading to a more advanced or reliable model can enhance the efficiency and control of your AHU. 

Leaks in ductwork 

Leaks in the ductwork of air handling units (AHUs) lead to energy loss and reduced efficiency of the system. It’s important to identify and address these leaks promptly to maintain the performance of your AHU. 

Troubleshooting tips 

Regular inspections of ductwork: 

  • Regularly inspect the ductwork for signs of leaks, holes, or disconnections. This includes both visible and hard-to-reach areas. 
  • Look for any signs of wear or damage, such as rusting or corrosion, which can lead to leaks. 
  • Pay particular attention to the areas where the ducts connect to the AHU and at joints and bends, as these are common places for leaks. 

Using appropriate sealants or tapes for repairs: 

  • Identify the specific type of ductwork material to choose the right sealant or tape. For instance, metal ducts may require a different sealant compared to flexible ductwork. 

  • Apply mastic sealant or metal tape to any visible leaks. Avoid using duct tape as it tends to degrade over time. 
  • Ensure that the application is thorough and covers the entire area of the leak for an effective seal. 

Securing ductwork joints and connections: 

  • Ensure that all joints and connections in the ductwork are tightly secured. Loose connections can contribute to leaks. 
  • Use screws or clamps where necessary to reinforce these connections. 
  • After securing the joints, apply sealant or tape as an added measure to prevent leaks. 

Dirty coils 

Dirty coils in air handling units (AHUs) can significantly reduce their efficiency, especially in Perth and WA, where dust and outdoor elements can accumulate quickly. Coils play a vital role in heat transfer and keeping them clean is essential for the smooth operation of your AHU. 

Troubleshooting tips 

Implementing a regular cleaning schedule: 

  • Set a routine cleaning schedule for the coils. Depending on the environment, this could range from monthly to quarterly. 
  • Use a soft brush or a special coil cleaner to gently remove dirt and debris. Be careful not to damage the delicate fins on the coils. 
  • For thorough cleaning, consider hiring professionals who can use specialised equipment to clean without damaging the coils. 

Inspecting for corrosion or damage: 

  • Regularly check the coils for any signs of corrosion or physical damage. This is especially important in coastal areas where salt air can accelerate corrosion. 
  • If any damage or severe corrosion is found, it might be necessary to repair or replace the affected parts to prevent further inefficiencies or potential breakdowns. 

Ensuring proper drainage from the condensate pan: 

  • Inspect the condensate pan and the drain line regularly to ensure they are not clogged. A clogged drain can lead to water build-up and eventually mould growth. 
  • Clean the pan and flush the drain line to prevent water damage and mould, which can affect indoor air quality and the efficiency of the coils. 
  • Consider installing a condensate drain pan treatment tablet to reduce the growth of algae and mould. 

Unbalanced airflow 

Unbalanced airflow in AHUs can cause uneven heating or cooling in buildings, a common issue in varied climates like we have in Western Australia. This results in discomfort and inefficient energy use. Getting to the bottom of unbalanced airflow in AHUs is essential for maintaining a consistent and comfortable indoor environment. 

Troubleshooting tips

Regular checks and adjustments of dampers: 

  • Dampers in the ductwork play a crucial role in controlling and balancing airflow. 
  • Regularly inspect these dampers and adjust them to ensure that air is evenly distributed throughout the building. 
  • Pay particular attention to areas where airflow seems weaker or stronger and adjust the dampers accordingly. 

Inspecting and adjusting fan speed settings: 

  • The fan speed in the AHU can affect airflow balance. Too high or too low speeds can lead to uneven distribution. 
  • Check the fan speed settings and adjust them for optimal air distribution. This might require some trial and error to get right. 
  • Ensure that the fan is operating efficiently and not hindered by mechanical issues such as worn bearings or misalignment. 

Professional airflow analysis and adjustments: 

  • For complex systems or persistent issues with airflow balance, consulting a professional is advisable. 
  • They can conduct a detailed airflow analysis to identify the root causes of imbalance. 
  • They can also make the necessary adjustments and recommend solutions such as duct modifications or additional vents to improve airflow.a 

How IACS can be of service 

For some minor problems, you may be able to troubleshoot and fix your air handling unit (AHU) on your own. However, for more complex issues, it’s always best to consult professionals like Independent Air Conditioning Solutions (IACS). If you encounter a problem with your AHU—or any product purchased from IACS that’s still under warranty—our team is prompt in dispatching a technician to address the issue. This ensures that any warranty-covered problems are quickly and professionally resolved, minimising inconvenience and ensuring your system is back to optimal functioning as soon as possible. For more information, check the warranty status of your product or contact our team for support. 

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