Fan Coil Units consist of a cooling coil which looks very much like the radiator in a car. The cold water typically comes from a water or air chiller in large commercial buildings. The fan in the FCU pushes air across the coil and cools the air while heating the water, therefore removing heat from the atmosphere within the room.
The now warmer water is pumped back to the plant room where it is cooled through an air or water cooling system before then being pump back down to the room. This is the cycle for such equipment and it is a closed system, so does not require a great deal of water once up and running.
Fan coil units are a piece of equipment typically located within the room. They are reasonably low maintenance because there is usually no compressor or refrigerant gases within a fan coil unit.
Hotel rooms are one of the most common locations to find an FCU. If you have ever seen the vent near the entrance to the hotel room , chances are there is a fan coil unit located in the ceiling. Individual temperature controllers in each room are stand alone, but can be networked into a buildings BMS system.
Fan coil units may not last as long as chillers and water cooling towers so it is not uncommon to have to replace fan coil units at intervals of between 10 to 20 years. This depends on their usage and proximity to the ocean in many instances. Hygiene is an issue because the coils are typically cool and do need to be cleaned regularly and the coils protected. As with any other piece of equipment, dust accumulates in the units and it is therefore important to clean the filters regularly.
In Australia where temperatures are warmer, fan coil units run mostly on cold water to cool rooms for air conditioning. An electric heater is often located within a fan coil unit and the fan drives air across the element to warm it in the winter months. Buildings in the northern hemisphere, where winter temperatures are a lot lower in winter, will often have both a cooling and heating water system so in effect the unit simply changes the water temperature in order to either heat or cool the room.