What is the difference between VAV and FCU?

VAV - Variable Air Volume

         It's just a mechanical device used to control the air flow of the duct.There is a actuator which is connected to the shaft of the damper.So we can control the airflow by varying the voltage of actuator.

FCU - Fan Coil Unit

        This is the miniature of the air handling units.It is operated by the cooling water.

VAV stands for Variable Air Volume. The VAV  regulates the quantity of already cold or hot air that is entering a room with the use of a damper.This damper is set in a constantly changing position and it controls the amount of air that  passes through the VAV unit.

FCU stands for Fan Coil Unit. The FCU has a fan inside(can be with VFD) and a heating or cooling coil. The fan pushes the air through the FCU and the hot or cold water/refrigerant liquid passes through the coil, which is inside the air flow path, heating or cooling the air.

Hi Muhammed,

VAV and  FCU are two very different things and the only similarity between the two is they are used in HVAC system.

VAV stands for Variable Air Volume &

FCU stands for Fan Coil Unit.

VAVs are like automated volume damper which is installed to regulate the flow of air in conditioned space according to the thermostat setting.

On the other hand FCU is the equipment used to condition the space it can either be a DX or Chilled water system.

FCU HAS 3 FAN SPEEDS WHICH COULD BE CONTROLLED BY ITS THERMOSTAT,WHERE AS VARIABLE AIR VOLUME HAS A VAV BOX OF ITS OWN WHICH HAS A DAMPER FOR AIR FLOW AND VARIABLE SPEEDS CAN BE ATTAINED WITH DESIRED TEMPERATURES WITH THERMOSTAT