What is an Air Handling Unit (AHU) and It's Function?
Updated: Oct 18, 2022
An air handling unit (“AHU”) is a standard piece of equipment that you’ll see in large and small industrial or commercial spaces. They are responsible for providing fresh air to different areas of the building.
Being the heart of the larger HVAC system (heating, ventilating, and air conditioning), the AHU manages ventilation by collecting outdoor air and room air (air already present in the building), filtering the air, adjusting the temperature and humidity, and then distributing a comfortable and refreshing supply of air-conditioning through ductwork inside the rooms of the building.
Function of an Air Handling Unit
The AHU is designed for spaces like hotel dining halls, function rooms, restaurants, and conference or convention centres that have restricted natural ventilation due to their high volume of simultaneous visitors.
It is also a good solution for locations with strict hygiene regulations, like manufacturing facilities, clean rooms, medical operating rooms, and laboratories. AHUs can also be utilised to ventilate spaces that, for instance, have underfloor heating or radiators for air conditioning.
Application of an Air Handling Unit
AHU can be set up on a rooftop, basement or alongside the outside of a building wall. It produces cooled or heated air and sends it to the rooms for cooling/heating. In contrast to regular industrial air conditioners, AHU are commonly custom made according to each individual’s or building’s requirements.
AHU can be custom designed by means of internally mounting a filter, humidifier and different parts to regulate temperature, humidity, air flow and air cleanliness.
Components of an AHU
The component where outside air is pulled in, cleaned and distributed throughout the rooms. They can also pull indoor air that has been "recycled."
The air filtration equipment used will have a higher or lesser retention of particles, viruses, bacteria, odours, and other air contaminants based on the requirements for air purity. The filter will need to be changed on a regular basis.
Blower or fan
This electromechanical mechanism drives the air out of the AHU and into the ducts, where it is distributed throughout the rooms.
Heat exchangers are components that allow the temperature to be transferred between two fluids, in this case air and coolant, across a solid barrier.
Air going through this module is cooled by the cooling coil. Water droplets may be produced during this process, and the built-in droplet separator allows them to be collected in a condensate tray.
These are coatings that significantly lower the installation's noise level.
Plenums are placed at void areas where the air flow is homogenized.
Types Of Air Handling Units
1. Horizontal and vertical units
Vertical units typically require less floor area.
2. Draw-through and blow-through units
The AHU is either a blow-through or draw-through mechanism depending on where the fan is located. The later AHU is the more commonly found.
3. Outdoor air (makeup air) or mixing units
While mixing units (as the name suggests) can utilise both recirculating air and outside air, makeup air units use only outdoor air.
4. Single-zone and multi-zone units
For dual-duct systems, a multi-zone AHU is more frequently employed
5. Rooftop and indoor units
There are specific AHU made for usage outside. They resist corrosion and are typically positioned on the roof. However, the majority of AHU are indoor units.
6. Custom-built and field-built units
Standard units are lower in cost and quicker to deliver. More versatility is available with custom-built AHU, which may also be made to be the most energy-efficient option.
Purpose of an Air Handling Unit
An AHU’s main objective is to increase energy effectiveness. Picking up discarded heat and reprocessing it through the AHU is done in conjunction with heat exchanger cooler units and specialised "run around" coils. This feature lowers the demand placed on the heating coils and manages energy consumption.
Indoor and outside air are mixed during the cooling process to reduce the extreme hot/cold contrast when the air reaches the cooling coil and enable the unit to produce cool air with the least amount of energy.
All in All
One great thing about AHU is the ability to install many AHUs at one exterior site. Outdoor commercial air conditioning units are typically mounted on rooftops or along the exterior walls of buildings, but internal units must be installed separately in each room.
Additionally, it costs money and takes time to maintain each indoor unit that is installed in a room. AHUs, in contrast, can be erected collectively in a single outside site, allowing maintenance to be carried out there.
AHUs are not without flaws. The building as a whole won't have air conditioning if the AHU breaks down. In order to offer backup, it is important to build multiple AHU.
Air Handling Units manufactured and assembled by TCW Group