Difference Between AHU and FCU

AHU is Air Handling Unit and FCU that, is Fan Coil Unit are two integral parts of the HVAC. HVAC is an acronym for Heating, Ventilating, and Air Conditioning systems. It is common to get confused between the two terms sometimes, but as it seems, they are way too different from each other and can be easily distinguished.


The main difference between AHU and FCU is that AHU or the Air Handling Unit mostly takes care of the outside air. On the other hand, FCU, or the Fan Coil Unit, mostly takes care of recycling the inside air or, as it may seem, re-circulating the air. There are some more aspects under which these two terms can be clearly distinguished.


AHU or more commonly known as the air handling unit is a box-shaped accessible unit that is also called modulus and is used to purify indoor air on-premises. It helps in meeting the ventilation requirements in a building or a house and also assists in air conditioning.

FCU or more commonly known as the fan coil unit is a refining or recycling unit that is comparatively smaller in size than the air handling unit. It is also noticed that the fan coil unit is much noisier as compared to the air handling unit, which is seen as a problem.

Comparison Table Between AHU and FCU

Parameters of ComparisonAHUFCU
Full formAHU is more known as Air Handling Unit. FCU is more known as Fan Coil Unit.
SizeIt is a big unit.It is a comparatively smaller unit.
DuctsIt has ductwork to channel air.It does not have Ductwork to channel air.
SectionsIt has to humidify and reheat sections.It does not have any reheating or humidifying sections.
AirIt is made to treat the outside air.It is made to re-circulate or recycle the air.

What is AHU?

An air handling unit is a very important part of the HVAC system or more commonly known as the heating ventilating and air conditioning system. It is very big in size and has the shape of a box, which are called modules. The installation process starts by placing it on the building rules and then circulating air inside the whole building with the help of ducts. The ductwork in the air handling unit is very important and needs to be taken care of in terms of cleaning and damage. Also, the Air Handling Units are less noisier as compared to the Fan Coil Units.

The air handling unit mostly uses the outside air, treats it, and then circulates it inside the building or premises with the help of ducts. The main function of an AHU is ventilating the interior of a building outside air. Other features of an air handling unit include controlling and filtering the quality of air using purification filters, controlling the temperature of the air, and helping in regulating the air-conditioning inside the building. It also controls the relative humidity in order to provide a comfortable indoors. An air handling unit is made up of an air intake system, heat exchangers, filters, silencers, fans, cooling coil, and plenums. All these parts work in sync with each other and provide the best outcome.

What is FCU?

The fan coil unit is yet another important and integral part of the heating, ventilating, and air conditioning system. This FCU unit is found in HVAC systems that are installed in commercial residential as well as industrial buildings. The very basic feature of this unit is to refine or, more precisely, recycle the inside air. It is made up of a fan and a heat exchanger, which is the coil component. These units are much smaller in size as compared to their handling units. There is also very limited use of ducks which feels negligible to mention. It is a very flexible and simple system that provides fresh air at a very low cost.

There is a drawback factor in the fan coil units, which is the noise they make. In comparison to air handling units, the noise that FCUs create is very high, but when we compare them to normal air conditioning systems, it is regarded as an acceptable decibel. As its name already mentions, the fan component of the unit is responsible for cooling the air and bringing it to the required temperature. The speed of fan motors can be regulated in order to control the cooling and heating air output.

Main Differences Between AHU and FCU

  1. AHU stands for or expands to Air Handling Units, whereas FCU expands to Fan Coil units.
  2. AHU is a lot bigger in size, while on the other hand, FCU is smaller.
  3. In order to channel the air, the Air Handling Unit has ducts. On the other hand, there is no such system of ductwork in a Fan Coil Unit.
  4. An Air Handling Unit is used to treat the outside air. A Fan Coil Unit is used to recycle the air.
  5. An Air Handling Unit has to humidify and reheat sections, whereas a Fan Coil Unit does not have reheating or a Humidifying section.


The Air Handling Unit (AHU) and Fan Coil Unit (FCU) are two of the very important parts of the Heating, Ventilating, and Air Conditioning systems that are installed in all types of buildings from commercial to Industrial. The main role of these units is to control and regulate the temperature of the air inside the premises and maintain a comfortable indoor atmosphere.

Where on the one hand, the AHU helps in providing regulated air inside the building by refining and purifying the intake outside air. On the other hand, the FCU helps to regulate and keep a comfortable temperature indoors by refining the indoor air only. They are both very important and must be taken care of by the regular cleaning and maintenance of the ducts as well as core system units. A proper maintenance check must be done in regular intervals of time for efficient working of the system.


  1. https://www.sciencedirect.com/science/article/pii/S0360132314003989
  2. https://www.mdpi.com/936286
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