A Comprehensive Guide on Air Handling Units (AHUs)

Just like other components, air handling units (AHUs) are a vital element of heating, ventilation, and air conditioning (HVAC) systems. These units are crucial in managing oxygen intake and circulation within a building to ensure that the environment within is conducive for safety and comfort. These systems are used in the healthcare sector, commercial buildings, as well as in industrial facilities, and make sure that air is filtered and distributed properly. In this article, the working principle, components, types, benefits, and maintenance of air handling units is presented.

Air Handling Unit (AHU) Definition

An AHU can also be referred to as a unit ventilator, and is defined as any piece of equipment found in the HVAC system that treats and distributes large volumes of air. It is positioned externally to a building, spending outside air that is clean through a filter and heats or cools the building as needed. Distribution of air is then done in an even manner to the rest of the building. Dispersing used air from a room is also considered and possible because of AHUs, which help improve the quality of air available in the room and therefore assist with other forms of ventilation.

AHU (Air Handling Unit) Operation

The operation of an air handling unit is comprised of the following steps:

First, air comes from two places: fresh air duct from outside and used air from inside the building (called return air) through return air duct. These two types of air from ducts meet and mix in a place called the mixing chamber.

After mixing, the air moves through filters. Filters are like nets that catch dust, dirt, and other small things in the air. This makes the air clean and safe to breathe.

Next, the clean air goes to another part called the cooling or heating coil. If the air needs to be cooled, the cooling coil makes it cooler. If it’s a cold day and the air needs to be warmer, the heating coil makes it warm. This step ensures the air feels comfortable for everyone.

Finally, a machine called a blower (like a big fan) pulls the clean, comfortable air and pushes it through supply air ducts. These ducts carry the air to different rooms in the building, making sure that every room gets fresh, clean, and comfortable air.

This process keeps the air in a building healthy, clean, and at the right temperature, so people inside feel good and stay healthy. The AHU does all this work quietly and efficiently in the background.

Fundamental Parts of an AHU

AHU is composed of many parts, and each part is essential to the unit, serving a specific purpose:

• Air Filters – Purifies the air by removing unwanted solid particles that contaminate it.
• Cooling/Heating Coils – Heats or cools the air by either removing or adding heat to it.
• Blower/Fan – Propels the air through the unit.
• Air Damper – Controls the discharge of air from a space or system and aids in the pressure equilibrium.
• Humidifiers/Dehumidifiers – Increases or decreases the moisture content of the air to a desired level.
• Mixing Box – Increases efficiency by bringing together unpolluted air and previously ventilated air.
• Control System – Oversees the operations of the AHU, including temperature adjustment or vent modulation.

Types of air handling units in the market

there are different types of Air handling Units

Packaged Air Handling Units (PU or RTU)

These are the machines that assist in the management of air in buildings, these units Cool, heat, filter and also distribute air, All components such as: fans, filters and cooling systems are integrated into one compact enclosure, units are mounted either on the roof or the external wall, used in office blocks, shopping complexes, and industrial factories for air conditioning. They are very easy to install and are fully automated.

Terminal Units

Air conditioning terminal units, sometimes referred to as terminal units,form part of the HVAC unit with the function of supplying conditioned air to a designated space such as a room for heating, cooling and ventilation applications, these also work in controlling air and the different circumstances of the room.

Makeup Air Units (MAU) or Fresh Air Handling Units (FAHU)

Make Up Air Units (MAU) FAHU stands for Fresh Air Handling Units, these are responsible for supplying outdoor air to buildings, these also purify the air, change the old air and promote healthy air to breathe.

Hygienic Air Handling Units

Hygiene Air-handling units are designed to convert air into non-harmful air, thus safe for human consumption. These are utilized in hospitals, labs, and food manufacturing facilities, even chewing gum factories. These machines work in eliminating moisture, heat and ensure the environment is clean. Specialized filters are installed to remove wooden dust, bacteria and other harmful particles ensuring the air is free of contaminants. Anything which could have led to an increase in the likelihood of getting infected has been tackled buoyantly. Where clean air is essential for any health or safety issue, Hygienic AHUs have proved tremendously beneficial. These machines ensure the air is devoid of any impurities

Ceiling-Mounted Air Handling Units

Ceiling-mounted air handling units are machines placed on ceilings to control room air. They help keep the air clean, cool, or warm as needed.

Modular Air Handling Units

Modular Air Handling Units are machines used in buildings to clean, cool, or heat air. They are easy to install, flexible, and save energy, too.

Variable Air Volume (VAV) and Constant Air Volume (CAV) Air Handling Units

Variable Air Volume (VAV) and Constant Air Volume (CAV) are systems used to control air in buildings. VAV adjusts airflow as needed, saving energy. CAV keeps airflow steady all the time.

Compact Air Handling Units

As its name describes, a compact air handling unit is a device that helps clean the air and is small in size and through its size it is able to cool air and make it easier to breathe. Such devices are placed inside a building to ensure that the air in the room is fresh as well as comfortable.

Industrial Air Handling Units

Industrial air handling units (AHUs) help clean and move air in significant buildings. They keep the air fresh, cool, or warm as needed.

Energy Recovery Ventilation (ERV) and Heat Recovery Ventilation (HRV) Units

Energy Recovery Ventilation (ERV) and Heat Recovery Ventilation (HRV) units help bring in fresh air while saving energy. They remove stale air and keep homes comfy.

Uses of an Air Handling Unit

• Improved Indoor Air Quality – Air is filtered as it goes through the system, removing dirt and contaminants to ensure cleaner air for use.
• Energy Efficiency – The energy used for heating and cooling in the AHU's system is reduced with energy recovery, making it more efficient.
• Consistent Temperature Control – The unit maintains a steady indoor climate.
• Humidity Regulation – The level of moisture or dryness is regulated to ensure it does not exceed a certain level.
• Noise Reduction – Advanced designs of AHUs have reduced the amount of noise produced while in use.

Useful Maintenance Suggestions to Maintain Peak Performance

Like any other equipment, using an Air Handling Unit (AHU) entails regular maintenance to ensure smooth operation. Here’s what you can do to maximize efficiency:

• Change or Clean Filters – Filters should be replaced or cleaned when airflow is noticeably reduced.
• Examine Fans and Motors – Regularly check them to prevent expensive failures.
• Look for Dirt or Matter Obstructing Coils – Clean coils ensure optimal heating and cooling.
• Watch Excess Water and Humidity – Prevent mold growth and excess moisture.
• Schedule Specialist Examination – Regular professional inspections help detect and resolve issues early.

General Queries Related to Air Handling Units

1. How long will an AHU last?
   • The lifespan of an AHU ranges from 10 to 25 years, depending on usage and maintenance.
2. Am I able to increase energy efficiency with an AHU?
   • Yes. Energy recovery AHUs and variable-speed fans significantly reduce energy consumption.

• How frequently do filters need replacement?
  • Filters should be replaced or cleaned every 3 to 6 months, or more frequently in dusty environments.
• Illustrate an AHU and HVAC system in the context of each other. Are they synonyms?
  • No. An AHU is a component of an HVAC system, responsible for air treatment and circulation.
• For my building, what is the ideal AHU size?
  • The size of an AHU depends on the building area, number of occupants, and ventilation needs. Consult an HVAC professional for recommendations.

Conclusion

AHUs are critical components of modern HVAC systems. Along with other elements, they regulate indoor air quality, energy efficiency, and comfort. Proper selection, installation, and maintenance of an AHU significantly influence building performance and occupant well-being. To ensure optimal efficiency, it is best to choose suitable AHUs and follow routine maintenance. If you are considering installing or upgrading an AHU, consulting an HVAC specialist is advisable to align the system with your specific needs.