Functions of Air-Handling Units

Functions of Air-Handling Units Points : Functions of Air-Handling Units, Air-Handling Units An air-handling unit (AHU) is the primary equipment in a system of a central hydronic system it handles and conditions the air and distributes it to various conditioned spaces. In an AHU the required amount of out door air and re-circulating air often mixed and conditioned. The temperature of the discharge air is then maintained within predetermined limits by means of control system. After that, the conditioned supply air is provided with motive force and is distributed to various conditioned spaces through, ductwork - and space diffusion devices. Many air-.handling units are modular So that they have the flexibility to add components as requited. AHU basically consists of an outdoor air intake and mixing box section a fan section including a supply fan and fan motor, a coil section with a water-cooling coil, and a humidifier may also be included depending on the application. Supply volume flow rates of AHU vary from 2000 to 63,000 cfm, (945 to 29. 730 L/S). Whether a return fan or a relief fan should be added to an air system depends on the construction and operating characteristics of the air system and the total pressure loss of the return system. A heating coil is mainly used in the air conditing unit that serves the perimeter zone or for morning warm—up the heating season. The use of a pre cooling coil to cooling water from the cooling tower as a water economizer is discussed humidifiers are employed for processing air conditioning and health care facilities where space humidity must be controlled.

Casing The external cabinet is usually made of 18-gauge. (1.3mm) galyanized steel sheet with a corrosion-resistant surface coating. The cabinet is lined with insulation to prevent outer surface condensation.

Although there are fins, water coil, and filters in both fan-coil unit and air-handling unit, a fan coil unit is distisiguished from an AHU by the following.