airhandlingunit

An air handling unit (AHU) is a central component of HVAC systems in commercial, institutional, and industrial buildings. It conditions and circulates air by taking in outdoor air and recirculated return air, filtering it, and delivering it to occupied spaces through a duct network. The AHU often serves as the primary air management point, coordinating with other equipment such as chillers, boilers, and energy recovery devices.

Common AHU components include a filter section, heating coil, cooling coil, supply fan or blower, and dampers for intake, exhaust, and outdoor air. Many units incorporate sound attenuators, a humidifier, and an energy recovery device such as a heat recovery wheel or plate exchanger. Controls and sensors regulate temperature, humidity, pressure, and ventilation rates, often via a building management system. Some AHUs use variable air volume (VAV) or constant air volume (CAV) configurations and may include economizers to take advantage of favorable outdoor conditions.

Operation: Outdoor air and return air are mixed and conditioned by coils, then supplied at a controlled temperature and humidity level. Return air completes the loop. The AHU can be sized for peak loads and operates in coordination with other HVAC equipment. Energy efficiency features include high-efficiency motors, variable frequency drives (VFDs), energy recovery, and efficient filtration.

Placement and terminology: AHUs are installed in mechanical rooms, basements, or on rooftops (rooftop units, RTUs). In larger buildings, multiple AHUs may serve different zones.

Standards and maintenance: AHUs are designed to comply with standards such as ASHRAE guidelines and EN 1886 for air handling units. Regular maintenance includes filter replacement, coil cleaning, belt or motor replacement, damper and actuator checks, and control calibration to ensure performance and indoor air quality.