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]
- 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:
|Description||Fan Coil Unit [FCU]||Air Handling Unit [AHU]|
|Cost||Pretty reasonable||Can be very expensive|
|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|
|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|
|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|
|Mounting||Slab [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||Easy||Easy, unless at high level then more complex due to size and weight of components|
|Maintenance Space||Not a lot required||Quite a large allowance to open doors and extract components/coils etc.|
|Onsite Installation||Simple||Simple, 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‘.