As part of a heating, ventilation, and air-conditioning system, an Air Handling Unit (AHU) is used to recondition and circulate air. The AHU's primary function is to take in outside air, recondition it, and supply it to a building as fresh air.
The Air Handling Unit (AHU) is a device that circulates air. HVAC stands for heating, ventilation, and air conditioning. The central unit to which the AHU is attached is the HVAC. AHU is a subset of HVAC, thus there isn't much of a distinction between the two.
Only an air filter, coil, and blower are included in terminal units.
Makeup air units are larger air handlers that condition 100% outside air instead of recirculated air.
Rooftop units are air handlers that are positioned on roofs and are suited for outdoor use.
RTU is for Rooftop Unit while AHU refers for Air Handling Unit. The Roof Top Unit is an AHU that is located outside. Because the RTU is located on the roof, there is no need to worry about having enough space or area to install it, as there is with other forms of AHU.
The AHU is often a huge metal box that connects to the ductwork that distributes conditioned air throughout the building before returning it to the AHU. AHUs provide the room with fresh air. The units collect outside air, filter it, and recondition it (cooled by a cooling coil or heated by a heating coil).