What is the difference between air handling unit and the fan coil unit?

Answer 1

AHU v/s FCU

AHU and FCU are both included in the HVAC system. The latter is an acronym that describes multiple systems of heating, ventilating and air conditioning. AHU, completely known as air handling unit is different from FCU or the fan coil unit.

AHUs are usually connected to a central HVAC system whereas an FCU can function or be installed itself. Because of this, it is often the AHU that is used to ventilate an entire building whereas FCUs are used in smaller and often local spaces only. It is no surprise that AHU is the bigger HVAC system not to mention, the FCU is also regarded as the smaller version of the AHU. In this regard, the smaller FCUs can be called terminal units.

Because of the magnitude of the AHU system, it usually makes use of the air from the outside environment. Thus, it treats outside air and brings it inside the vicinity with the use of special ducts while an FCU system on the contrary just circulates the inside air. The latter usually does not have any duct system that’s why it is obviously smaller in size as previously mentioned. It is only composed of a simple coil and fan.

Ordinarily, AHUs have certain features that are not present in the FCU type. AHUs have several sections for reheating and even humidifying. FCUs don’t have sections such as these. Perhaps the only advantage that the FCU has over the AHU is that generally, FCUs can also handle water while the AHUs basically handle air.
Moreover, AHUs can have several fans or blowers installed in its system. Traditionally, the AHU’s blowers are placed at the point where the ducts originate or at the terminal end of the air handler unit. FCUs have a different approach to blowers. Because of its small size, their fans are usually placed within the same space as the unit itself. The result is a minor uncomfortable noise that can be heard within the vicinity. This could be regarded as the single most advantageous flaw of the FCU system.

Summary:
1. AHU is generally a bigger system than FCU.
2. AHU is more complex than the FCU and that AHU are often used in bigger establishments or spaces.
3. The AHU system usually channels air through ducts whereas the FCU don’t have any ductworks.
4. AHU system treats outside air while FCUs basically recycle or re-circulates the air.
5. AHU has sections for reheating and humidifying whereas the FCU does not have any.
6. FCU is often observed to be noisier than the AHU.