Exhibitor News

Your air handling unit works quietly in the background, maintaining comfortable temperatures and fresh air throughout your building.

When it’s functioning properly, you barely notice it’s there. But when problems develop, the consequences can be significant: uncomfortable occupants, rising energy bills, and potentially expensive emergency repairs.

The good news is that most major AHU failures don’t happen without warning. In our 50 years of maintaining air handling systems across the UK, we’ve found that equipment almost always signals distress before complete breakdown. Recognising these signs early can save you thousands of pounds in emergency repairs and prevent disruption to your operations.

Here are the five warning signs that your air handling unit needs urgent attention.

1. Unusual or Increasing Noise Levels

Air handling units produce a consistent background hum during normal operation. If you notice new noises or existing sounds getting louder, your AHU is telling you something’s wrong.

What to Listen For

Grinding or scraping sounds typically indicate bearing failure in the fan assembly. Bearings wear over time, and when they start to fail, metal-on-metal contact creates characteristic grinding noises. Left unaddressed, a failed bearing can cause the fan shaft to seize, potentially damaging the motor and requiring extensive repairs.

Banging or rattling suggests loose components. Fan impellers can work loose on their shafts, access panels may have failed latches, or internal components might have come adrift. While this might seem minor, loose parts can cause vibration that accelerates wear throughout the system and may eventually cause more serious damage.

High-pitched whistling or whooshing often points to airflow restrictions or pressure imbalances. This could indicate heavily soiled filters creating excessive resistance, or damper problems causing turbulent airflow. These issues force the system to work harder, wasting energy and potentially causing motor overload.

Clicking or humming from motors may signal electrical problems. Contactors may be failing, or the motor itself could be developing faults. Electrical issues require immediate attention as they pose safety risks and can lead to complete system failure.

What You Should Do

Don’t ignore unusual noises. Schedule an inspection as soon as possible to identify the source. Early intervention often means a simple adjustment or component replacement. Delay can turn a minor issue into a major failure requiring emergency callout and expensive repairs.

2. Temperature Inconsistencies or Inability to Maintain Setpoints

If your air handling system struggles to maintain comfortable temperatures, or if some areas are too hot while others are too cold, there’s likely an underlying problem.

Common Causes

Failing heating or cooling coils lose efficiency over time. Corrosion can reduce heat transfer surface area, or internal fouling can restrict water flow. The system runs continuously trying to achieve setpoints but never quite succeeds, wasting energy while failing to deliver comfort.

Control system malfunctions can cause erratic operation. Sensors may have drifted out of calibration, giving false readings. Control valves might be sticking or failing to modulate properly. The result is temperatures that swing above and below target or zones that never reach the desired conditions.

Airflow imbalances mean some areas get too much or too little air. This might result from blocked dampers, heavily soiled filters in some sections, or changes to the building layout that the system hasn’t been adjusted to accommodate.

Refrigerant or water flow issues in cooling and heating circuits prevent proper heat transfer. Low refrigerant levels, airlocks in water systems, or failing pumps all manifest as inability to achieve temperature targets.

What You Should Do

Temperature problems impact occupant comfort and productivity immediately. They also waste significant energy as the system runs unnecessarily. Have a qualified engineer inspect the system to diagnose the root cause. Often, recalibration, cleaning, or component replacement can restore proper operation quickly.

3. Rapidly Rising Energy Bills

Your air handling system typically accounts for a significant portion of building energy consumption. When something goes wrong, energy waste often provides the first measurable indication.

Why Energy Consumption Increases

Dirty filters are the most common culprit. As filters accumulate dust and debris, they restrict airflow. The fans must work harder to maintain the required air volume, consuming more electricity. In extreme cases, restricted airflow can cause motors to overheat and fail.

Failing motors and drives become less efficient as they age. Bearings create friction, insulation deteriorates, and electrical resistance increases. The motor draws more current to deliver the same output, showing up as increased consumption on your energy bills.

Compromised insulation allows heat transfer through the AHU casing. In summer, warm ambient air heats the supply air, making cooling less effective. In winter, heat escapes, reducing heating efficiency. Either way, the system must work longer to achieve setpoints.

Control problems can cause the system to run when it shouldn’t or prevent economiser cycles from operating. Dampers stuck in incorrect positions waste energy by bringing in too much outside air when it’s extreme, or failing to use free cooling when conditions allow.

Leaking dampers and poor seals allow supply and return air to mix, reducing system efficiency. The unit must condition more air than necessary to achieve the required result.

What You Should Do

Compare your recent energy bills to previous periods. Significant unexplained increases warrant investigation. An energy audit can pinpoint where waste occurs and quantify potential savings from maintenance or upgrades. Often, the energy savings from remedial work pay back the investment quickly.

4. Deteriorating Indoor Air Quality

Poor air quality affects health, comfort, and productivity. If occupants complain about stuffy conditions, odours, or increased allergies and respiratory issues, your AHU may be part of the problem.

How AHUs Affect Air Quality

Blocked or saturated filters stop removing contaminants effectively. Particles that should be captured pass through into occupied spaces. Worse, severely soiled filters can become sources of contamination themselves as captured material degrades and releases odours or spores.

Biological growth can develop in AHUs if conditions allow. Cooling coils create condensation, and if drainage is inadequate, standing water provides ideal conditions for bacteria and mould. These organisms contaminate the air stream, potentially causing health issues and definitely creating unpleasant odours.

Inadequate fresh air intake means elevated CO2 levels and stale air. This might result from damper failures, control problems, or changes to building occupancy that exceed the system’s capacity. High CO2 concentrations cause drowsiness, headaches, and reduced cognitive function.

Contaminated ductwork can harbour dust, debris, and biological growth that continuously contaminates the air supply. While not strictly an AHU problem, ductwork inspection should be part of any air quality investigation.

What You Should Do

Air quality problems require prompt attention, especially in healthcare or educational facilities. A thorough inspection should check filters, examine internal cleanliness, verify fresh air intake, and confirm that drainage systems function properly. Address any contamination immediately and establish proper maintenance schedules to prevent recurrence.

5. Visible Damage, Rust, or Water Leakage

Physical deterioration of the AHU itself signals serious problems that can affect both performance and safety.

What to Look For

Rust or corrosion on the casing, fan assembly, or internal components indicates moisture problems. This might result from condensation due to inadequate insulation, water leaks from coil connections, or blocked drainage. Corrosion compromises structural integrity and will eventually cause leaks or component failure.

Water on the floor around the AHU usually means condensate drainage problems. Blocked drain pans or pipes allow water to overflow. This can damage building fabric, create slip hazards, and provide conditions for biological growth.

Damaged or missing insulation exposes cold or hot surfaces to ambient conditions. This wastes energy through unwanted heat transfer and can cause condensation to form on cold surfaces, leading to drips and potential water damage.

Deteriorated seals around access doors allow air leakage between supply and return air streams, reducing efficiency. They also permit unfiltered air to enter the system, bypassing the filtration that protects air quality and downstream components.

Belt wear or damage on belt-driven fans can lead to unexpected failure. Cracked, glazed, or fraying belts should be replaced before they break, as belt failure shuts the system down immediately.

What You Should Do

Visual inspection should be part of regular maintenance schedules. When you notice physical deterioration, address it promptly. What starts as minor corrosion or a small leak can develop into major problems requiring extensive repairs if left unattended.

Taking Action: What Happens Next?

If you’ve identified one or more of these warning signs in your air handling system, the next step is professional assessment by a qualified HVAC engineer.

A comprehensive inspection will identify the root causes of problems, assess the overall condition of the system, and recommend appropriate remedial action. Sometimes, simple maintenance resolves issues quickly and inexpensively. In other cases, component replacement or system upgrades may be necessary.

The cost of proactive maintenance and timely repairs is invariably less than emergency callouts and the consequences of system failure. Regular servicing extends equipment life, maintains efficiency, and prevents the small problems that become expensive disasters.

Conclusion

Your air handling unit is a complex system with multiple components that must work together reliably. While robust and designed for long service, AHUs need regular attention to maintain performance and prevent failures.

By recognising these five warning signs early, you can address problems before they escalate. Unusual noises, temperature inconsistencies, rising energy consumption, poor air quality, and visible damage all indicate your AHU needs professional attention.

At i-Flow Technologies, we’ve spent 50 years maintaining, repairing, and refurbishing air handling systems across the UK. Our engineers understand how these systems fail and how to prevent problems through proactive maintenance.

Don’t wait for complete breakdown. If your AHU is showing warning signs, contact us for a comprehensive assessment. We’ll identify issues, recommend solutions, and help you keep your system running reliably and efficiently.