Air Handling Units or Fan Coil Units

The air handling units are very important parts of the central air conditioning plants, packaged air conditioning plants and also the roof mounted split air conditioning systems. As the name suggests air handling unit is the box type of unit that handles the room air. It comprises of the cooling coil over which the hot return air from the room flows, gets cooled and flows back to the room to cool it. The circulation of the air is carried out by the blower. The filter in the air handling unit enables cleaning of the air. The air handling units are also called as fan coil units in case of roof mounted split AC units, since they comprise of the fan and the cooling coil.

The air handling units are installed at the different places in the building to be air conditioned. They are connected to the cool air supply and return air ducts which are laid in all the rooms to be cooled. In case of the central air conditioning plants the air handling units are installed on the floor, while in case of the split air conditioners, they are mounted on the roof inside the room above the false ceiling. In case of packaged units they can be installed on the floor or the roof.

The various parts of the air handling unit and their working are discussed in details below:

All the parts of the air handling unit are enclosed in the box type of enclosure. This ensures compactness of the unit and protection of all the components inside it. The whole box is insulated to prevent the loss of heat from the unit.

The cooling is one of the most important parts of the air handling units. It is made up of copper tubing of several turns and covered with the fins to increase the heat transfer efficiency of the cooling coil. In direct expansion (DX) type of the central air conditioning plants the refrigerant flows though the cooling coil, which also acts as the evaporator of the plant. In case of the chilled water system the chilled water from the chiller flows through the cooling coil. In packaged and the split air conditioners also the refrigerant flows directly through the cooling coil, thus acting as the evaporator of the system.

The hot return air from the room flows over the cooling and gets cooled. This air is supplied to various rooms via the ducts. The flow of chilled water or the refrigerant to the cooling coil is controlled by the solenoid valve.