{"id":15103,"date":"2021-05-26T12:41:35","date_gmt":"2021-05-26T19:41:35","guid":{"rendered":"https:\/\/essential.construction\/academy\/?post_type=glossary&p=15103"},"modified":"2026-11-03T10:09:22","modified_gmt":"2026-11-03T17:09:22","slug":"air-handling-unit","status":"publish","type":"glossary","link":"https:\/\/essential.construction\/academy\/glossary\/air-handling-unit\/","title":{"rendered":"Air Handling Unit [AHU]"},"content":{"rendered":"

An air handling unit (AHU)<\/strong> is a large piece of HVAC equipment that conditions and circulates air through a building’s ductwork. A typical AHU houses a supply fan, filters, heating and cooling coils, dampers and sometimes a humidifier or heat recovery wheel, and is installed on the roof or in a mechanical room.<\/p>\n

How an air handling unit works<\/h2>\n
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  1. Outdoor air and return air from the building enter through dampers into a mixing box. The controls set the mix; in mild weather an economizer uses more outdoor air for free cooling.<\/li>\n
  2. Filters clean the air.<\/li>\n
  3. Coils heat or cool it. The cooling coil also removes moisture, which drains from a drain pan.<\/li>\n
  4. A humidifier adds moisture if needed.<\/li>\n
  5. The supply fan pushes the air through the ductwork<\/a> to terminal units (such as VAV boxes) and diffusers.<\/li>\n
  6. A return or exhaust fan draws air back, and an energy recovery wheel or plate can transfer heat between exhaust and incoming air.<\/li>\n<\/ol>\n

    Main components<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
    Component<\/th>\nJob<\/th>\n<\/tr>\n<\/thead>\n
    Casing<\/td>\nInsulated sections that contain the air; large units ship in pieces<\/td>\n<\/tr>\n
    Dampers<\/td>\nControl outdoor, return and exhaust air<\/td>\n<\/tr>\n
    Filters<\/td>\nPre-filters and final filters, rated by MERV in North America<\/td>\n<\/tr>\n
    Coils<\/td>\nChilled water or refrigerant (DX) for cooling; hot water, steam or electric for heating<\/td>\n<\/tr>\n
    Fans<\/td>\nSupply and return fans, often on a variable frequency drive<\/a><\/td>\n<\/tr>\n
    Drain pan and trap<\/td>\nCollects and drains condensate from the cooling coil<\/td>\n<\/tr>\n
    Energy recovery<\/td>\nWheel or plate exchanger that reuses heat or coolth from exhaust air<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

    Types of air handling units<\/h2>\n