Air Handling Unit Maintenance That Gets Results

Before we tell you how to perform air handling unit maintenance, lets cover the basics. It is important to understand what an air handling unit is and their key components before diving into how you can maintain them.

What Is an Air Handling Unit?

An Air Handling Unit (AHU), or an air handler, is a piece of equipment that is part of a larger overall HVAC system. These units are commonly found on rooftops, however variations of the unit may be found in utility rooms. Their sole purpose is to regulate air quality, temperature and humidity and then circulate that air in the system. AHU’s generally use ductwork to push the air they produce throughout the facility.

What Are The Main Components Of An Air Handling Unit?

Diagram of an air handling unit with parts

A basic diagram of an AHU. Set-ups vary from unit to unit. Photo courtesy of Bill Kosik

Blowers: commonly referred to as fans, are the heart of the AHU system. These are most commonly centrifugal fan and are what provide enough pressure for the air to be moved throughout the system. When these components fail is it commonly a bad relay, run capacitor, blower wheel or the blower motor itself.

– Heating or cooling element: This is most commonly a heating coil or a cooling coil. Depending on the thermostat setting the air is run over a coil before entering the ducting system.

– Filters Racks: These hold a bank of filters that help to remove particles from the air. The type, size and number of filter will vary depending on the unit. Depending on air quality these may need to be changed semi-annual, quarterly or possibly even more frequently.

– Humidifiers: To avoid discomfort caused by drier air in the colder months, a humidifier is used. This increases the humidity of the air as it goes through the system.

– Dampers: these control the amount of air going through the unit. Dampers can be manual or modulating depending on the design.

– Belt: These are commonly found near the fan motor and are changed as they begin to wear inside the unit.

– Heat Exchanger: These are commonly fitted to an AHU for energy efficiency. They allow for exiting conditioned air to increase or decrease the temperature of the incoming outside air. By recovering the residual heat in the exhausted gas, the fresh air introduced into the system is preheated.

Your Air Handling Unit Maintenance Checklist

Routine AHU cleaning and maintenance not only extends the life of equipment but reduces operating costs, downtime costs and troubleshooting costs. It helps mitigate the majority of these expenses because the issues are caught ahead of time.

Use the maintenance checklist below to ensure you don’t miss a step:

  • Trane IntelliPak being lifted with a crane to a rooftopExamine electrical disconnect
  • Examine control panel and boxes
  • Check contactors/starters
  • Tighten electrical
  • Examine control set points
  • Log amp readings
  • Examine return air dampers
  • Inspect outside air dampers
  • Examine relief air dampers (if applicable)
  • Inspect face & bypass dampers
  • Examine filter section
  • Change filters
  • Examine heating coil
  • Clean heating coil
  • Examine drain line & pan
  • Examine cooling coil
  • Clean cooling coil
  • Examine drain line & pan
  • Clean drain line & pan
  • Examine supply air fan
  • Clean supply fan and housing
  • Lubricate fan bearings
  • Check belts and sheaves on supply fan
  • Examine supply fan motor
  • Lubricate supply fan motor bearings
  • Examine return air fan (if applicable)
  • Clean return fan and housing
  • Lubricate fan bearings on return fan
  • Check belts and sheaves on return fan
  • Examine return air fan motor (if applicable)
  • Lubricate return fan motor
  • Examine exhaust air fan (if applicable)
  • Clean exhaust fan and housing
  • Lubricate exhaust fan bearings
  • Check belts and sheaves on exhaust fan
  • Examine exhaust air fan motor (if applicable)Service Techs Installing An HVAC
  • Lubricate exhaust fan motor
  • Check fan(s) rotation
  • Record and Check operating amps
  • Check temperature split across coil
  • Check expansion valve
  • Examine heating section (if applicable)
  • Change Thermostat Batteries
  • Examine heater safeties
  • Examine other accessories (if applicable)

As always, follow the manufacture recommendations and do not perform maintenance tasks you are not experienced with or trained on.

What are the most common problems with air handling units?

Common problems encountered with air handling units (AHUs) include:

  • Air Filter Issues: Clogged or dirty air filters can obstruct airflow, leading to reduced system efficiency and poor indoor air quality.
  • Coil Fouling: This involves the accumulation of dirt, dust, and debris on the evaporator and condenser coils. This can decrease heat transfer efficiency, resulting in poor performance.
  • Fan Motor Malfunction: Faulty fan motors can lead to inadequate air circulation, reduced airflow, and compromised temperature control.
  • Belt and Pulley Problems: Worn-out or misaligned belts and pulleys can cause excessive noise, reduced airflow, and increased energy consumption.
  • Leakage and Ductwork Issues: Damaged or poorly sealed ductwork can lead to air leaks, decreased efficiency, and inefficient air distribution.
  • Control System Failures: Faulty sensors, malfunctioning thermostats, or issues with the control panel can disrupt the AHU’s operation.

What is the maintenance frequency of AHUs?

The frequency of maintenance for air handling units depends on several factors, including your specific system requirements, manufacturer guidelines, and environmental conditions. As a general rule, AHU’s should undergo maintenance at least twice a year. This preventive maintenance schedule helps ensure optimal performance, energy efficiency, and prolongs the lifespan of the unit.

Contacting an HVAC professional can help determine the ideal maintenance frequency based on specific requirements and usage patterns.


Below is a list of parts you can keep in stock to limit further expenses!

  • Air filters
  • Belts
  • Capacitors
  • Coil Condenser Cleaners
  • Contactors
  • Fuses

For larger facilities, it can be cost-effective to build your inventory of more expensive replacement parts. Especially if you have five or more pieces of equipment sharing parts like:

  • MotorClose up of blower motor and belt assembly.
  • Capacitors
  • Gas Valves
  • Control Boards
  • Compressors
  • Bearings
  • Shafts
  • Impellers, etc.

Want Help With Your Air Handler Maintenance?

Talk to the maintenance Pro’s! One of our HVAC technicians can identify problems quickly and keep your system operating at peak efficiency. Allow an expert to check refrigerant levels, make adjustments to the blower, examine electrical connections and perform an overall wellness check on your system. This ensures your entire system is in good working condition can prevent breakdowns from occurring. Give us a call at 1-800-237-3141 or email  Our team is here to help!

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