Air Handling units are box units that handle room air and are a significant part of the central air conditioning plant. The cooling coil from which the hot air returns from the room flows, then cools and flows back into the room producing cool air from the blower. The air handling unit’s filter cleans the air. Roof mounted split air conditioning units consist of the cooling coil and the fan. Installation of air handling units can be placed in various areas of the building. These units are joined together with the cool air supply and return air ducts in the rooms that require cooling. The installation of the central air conditioners are placed on the floor and split air conditioners are mounted above a false ceiling on the roof. Packaged units can either be installed on the roof or floor.

The Cooling Coil

A significant part of the air handling unit is the cooling coil. The heat transfer efficiency of the cooling coil is made up of copper tubing with multiple turns and covered fins. Central air conditioning plants refrigerant moves through the cooling coil also acting as an evaporator. Chilled water flows through the cooling coil of the chilled water system and in packaged and split air conditioners the refrigeration flows through the cooling coil which in turn acts as the evaporator. The hot air that returns from the room moves over and cools. The air is then vented through ducts wherever required. A solenoid valve controls the flow of this refrigerant to the cooling coil.

Ducting

Air handling units are joined together with the supply air and return air ducts. These ducts supply the cool air from the units where needed and then the hot return air back to the air handling unit. The main duct bifurcates to multiple smaller ducts from all the areas to be cooled. These ducts then return to one main duct. The ducts are insulated to help the loss of any cooling effect. They are placed to ensure the cool air is evenly distributed in the required area.

Blower or Fans

The hot return air is sucked by blowers or fans from the area and over the cooling coil, then cools and returns it air-conditioned. Air handling units have two arrangements either a draw through an arrangement where the fan sucks the return air through the filter and then cools it. The air passing over the cooling coil gets chilled and flows through all areas that need cooling. The other a blow through an arrangement where a fan absorbs the air and then blows it over the air filter and cooling coil producing air conditioning. This method is the most common and the types of fans are centrifugal.

Air filter

A significant part of all air conditioning systems is the air filter. It removes smoke, dirt, dust and various other impurities. Usually, the air filter is attached to the cooling air. Firstly the air absorbs or pushes over the air filter and then goes over the cooling coil.