Air handling units, or air handlers, are a piece of equipment used to circulate and condition the air as a part of heating, ventilation and air conditioning systems. These handling units are generally a large metal box with a blower, some cooling and heating elements, filter chambers, sound attenuators and dampers. It connects to the ductwork, which further distributes the conditioned air, whether heated or cooled, throughout the building, before returning it to the AHU. However, there are also certain units that discharge and admit air directly to and from the building, without requiring a ductwork.
AHUs are usually found in medium to large industrial and commercial buildings, either located in the basement, on the rooftop, or the floors of the building. These units generally serve a specific area of zone in the building, hence you might spot multiple units in or around the building. Although you are likely to see old, high rise buildings with a single, large air handler, mostly located on the roof.
Air handling units can be of three types:
- Terminal Units: These types of units only include an air filter, coil, and blower. Such simple units are often referred to as blower coils or coil units.
- Makeup Air Units: These units are large air handlers that can condition 100% of the outdoor air, rather than recirculating the air.
- Rooftop Units: Rooftop units are air handlers that are specifically designed for outdoor usage and are placed on roofs.