Fan Coil Unit [FCU] vs Air Handling Unit [AHU]

Last Updated: August 16, 2023, by

So what is the difference between a fan coil unit and an air handling unit?

If we break down and compare the components of a fan coil unit and a simple 100% fresh air handling unit there is little difference to see between the two on the surface, as each would consist of the following:

  • an air Intake/inlet
  • an air filter
  • a motor driving a fan
  • a fan
  • some form of coil [cooling/heating or both]
  • pipework
  • controls/control valves
  • thermostat/temperature sensor
  • condensation drip tray
  • air discharge/supply

In this instance, the only real difference would be that the air handling unit operates by bringing in fresh air from the outside, whilst the FCU generally recirculates and conditions the air in the space it serves. They both move and condition air.

The below details a simple diagram of the basic components that they both have in common. 

Fan coil unit description

Fan coil units (FCU’s) are small single units that condition air and move it to the space via minimal ductwork. They can be used to manage small loads [KW], usually located in single rooms, recirculating the air.

They are quite versatile and inexpensive, having options to be installed in concealed in ceilings, exposed [out of ceiling], underfloor, or mounted vertically against a wall.

Air handling unit description

Air handling units [AHU’s] can be supplied as a complete single unit or in modules [components] that can be shipped to the site. If the unit is supplied in modules, during installation they will be bolted together to create a larger single boxed unit.

The air handling unit is designed, once installed and commissioned, to supply fully conditioned air [cooled or heated] to the multiple zones/spaces in the building allowing much larger loads [KW] to be managed than with the FCU.

The conditioned air that the unit creates is usually moved around the system via metal ductwork with the airflow being controlled by dampers and the temperature by valves [chilled/heating water].

FCU vs AHU Matrix

The units both on a drawing can look the same, but in actual fact, there are many differences that we have listed below:

DescriptionFan Coil Unit [FCU]Air Handling Unit [AHU]
Cost  Pretty reasonable  Can be very expensive  
Size [physical]  Small  Large  
Size/Capacity [KW]  around 12KW max  Over 100KW+  
Used for   Directly serving single spaces/rooms  Serves multiple zones   
Connected to  Flexible ducting to feeding grilles  Solid ducting serving multiple areas through building  
Air Volume  Small  Large  
Able to Cool  Yes  Yes  
Able to Heat  Yes  Yes  
Pipework configuration  2 pipe / 4 pipe  2 pipe / 4 pipe  
Airflow  Small  Can be large  
Noise  Low  Can be high  
Controls  Simple  Can be complex  
Variable Speed Drive [VSD]  Not usually  Yes should have  
Condensate pipework  Required  Required  
Manufacturing  Usually built as one complete unit  Usually manufactured in modules to allow easier shipping, movement around the site, and maintenance.  
Delivery Period  3-6 weeks  6-12 weeks  
Factory Testing  Usually not  Usually completed  
Transportation  Less expensive as more can fit on the vehicle  Can be quite expensive depending on the size  
Delivery and movement around the site  Quite easy [pallet truck]    Can require specialist handling equipment and resource  
Type of building installed  Commercial buildings, Industrial buildings, Office buildings, Hotels, Schools, Residential  Commercial buildings, Industrial buildings, Office buildings, Hotels, Schools.  
Installation location  Only internal spaces  Plant Room, Roof Top, External  
MountingSlab [Exposed] Ceiling [Concealed] Floor [Verticle]  Usually, Plinth on the floor or can be a high level but require additional supports.  
Access  Usually from the back or underneath  Usually from side  
Maintenance  EasyEasy, unless at high level then more complex due to size and weight of components
Maintenance Space  Not a lot requiredQuite a large allowance to open doors and extract components/coils etc.
Onsite Installation  SimpleSimple, depending on space available
Operating costs      Minimal as long as commissioned and set up correctly    As long as commissioned and set up correctly can be not too bad depending upon the size of motor and unit etc.  

So that’s it, a simple overview of the differences between an Air Handling Unit and a Fan Coil Unit.

If you want to read in more detail about Fan Coil Units then we have written an article ‘Fan Coil Units | What, Where & How‘.

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