Air Handler

An air handler , or air handling unit (often abbreviated to AHU ), is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning ( HVAC ) system. Usually, an air handler is a large metal box containing a blower , heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers . Air handlers usually connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. Sometimes AHUs discharge ( supply ) and admit ( return ) air directly to and from the space served, without ductwork.

Small air handlers, for local use, are called terminal units , and may only include an air filter, coil, and blower; these simple terminal units are called blower coils or fan coil units . A larger air handler that conditions 100% outside air, and no recirculated air, is known as a makeup air unit ( MAU ). An air handler designed for outdoor use, typically on roofs, is known as a packaged unit ( PU ) or rooftop unit ( RTU ).