What Is the Difference Between an Air Handling Unit and a Fan Coil?

What Is the Difference Between an Air Handling Unit and a Fan Coil?

This is a common question that can be easily confused since both involve the movement and cooling of air. An air handling unit (AHU) operates by bringing in fresh air from the outside, while a fan coil unit (FCU) generally recirculates and conditions the air in an interior space. Let’s see if we can break down how these systems work and alleviate the confusion.

Is a Fan Coil the Same as an Air Handler?

While both a fan coil and an air handler move air, they are different. Fan coil units are more simple systems, usually just a coil and a fan. FCUs are self-contained. They’re mostly used in commercial refrigeration systems, but occasionally, an FCU can be found in a short hallway to recirculate air instead of having ductwork there.

Air handling units, by contrast, are complex, typically bigger, and have several components. They are usually part of a central air system and connected to ductwork to distribute air.

What Are the Types of Air Handling Units?

Air handling units fall into two main categories:

  1. Draw-through handling units: Draw-through AHUs involve fans that draw or pull air through the mixing box, filters, a cooling coil, and air filters before it reaches the ductwork. This type of AHU can either be horizontal or vertical.
  2. Blow-through air handling units: The fans in a blow-through AHUs direct or blow air through the mixing box, cooling coil, and air filters, and then it ends up in the ductwork system.

Do Air Handling Units Have Refrigerant?

Air handling units may have refrigerant, but it depends upon the model. Basically, an air handler draws in outside air into a mixing box, so it blends with indoor air. When the air needs to be chilled, it’s passed through a cooling coil, and that coil is usually either water-cooled or uses a refrigerant. Then, the air moves through filtration and out to the ductwork.

Can an AHU Work Without a Chiller?

Yes, an AHU can function without a chiller. The main purpose of an air handling unit is, as the name indicates, to move air through the system and ductwork. If an AHU has a chiller, it’s a cooling system. If the AHU has an internal heat exchanger, it’s a heating system.

How Do FCUs Work?

A fan coil unit (FCU) moves air over a coil that is either a cooling or heating element, much like an air handler does. The difference is that an FCU is not connected to ductwork. As such, they can be easier and cheaper to install but will not be the optimal solution for all situations.

How Many Types of FCUs Are There?

Much like AHUs, there are primarily two types of FCUs. One is the draw-through, and the other is the blow-through. As the names indicate, the former pulls air, and the other pushes air.

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