Fan Coil Units (FCU) are standalone systems that use a fan and a coil to provide heating or cooling without ductwork.
These systems use hot or cold water from a central chiller/boiler, typically located in a mechanical room or on the roof. These units are less expensive than central HVAC systems and are usually installed in ceiling and floor-mounted configurations.
Major Components of a Fan Coil Unit (FCU)
A fan coil unit consists of the following components:
- Fan/Blower: Circulates air through the unit. Modern FCUs often use ECM (Electronically Commutated Motors) for better energy efficiency and speed control.
- Coils: Copper tubes with fins that facilitate heat exchange between the water and the air.
- Air Filter: Improves indoor air quality and prevents debris from depositing on coils.
- Drain Pan: Collects the condensation generated during the cooling cycle.
- Control Valve: Regulates the flow of hot or chilled water through the coils.
- Thermostat: Monitors the room’s ambient temperature and signals the fan coil unit to activate heating or cooling.
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How Does a Fan Coil Unit Work?
The operation of the FCU is straightforward:
- Air Intake: The unit’s fan draws air from the room through a return opening.
- Filtration: The air passes through a filter to remove dust and airborne particles, protecting the internal components.
- Heat Transfer: The filtered air then flows over the coil. If the room requires cooling, chilled water flows through the coil; if heating is required, hot water is used.
- Distribution: The conditioned air is then pushed back into the room to reach the desired temperature.
- Dehumidification: During the cooling process, moisture from the air condenses on the cold coil. This liquid drips into a drain pan and is piped away to a waste receptor.
This process continues until the desired temperature is reached.
Types of Fan Coil Unit (FCU)
Common types of fan coil units include:
- Vertical Fan Coil Unit (VFCs): These are upright units, often floor-mounted or concealed within closets. They are the preferred choice for high-rise residential buildings and hotels.
- Horizontal Fan Coil Units (HFC): Installed within ceiling voids or above drop ceilings, these units save floor space and are common in commercial offices and large hallways.
- Two-Pipe Fan Coil System: Such systems have only one supply and one return pipe and can provide either heating or cooling.
- Four-Pipe Fan Coil System: These systems have two supply and two return pipes, and can do both heating and cooling.
Application of Fan Coil Unit (FCU)
For their simplicity and individual zone control, fan coils are widely used in:
- Hotels
- Apartments and condominiums
- Office buildings
- Dormitories
- Hospitals and healthcare facilities
Do Fan Coil Units (FCU) Use Refrigerant?
Yes, fan coil units can use refrigerant, but it depends on the system configuration. In direct expansion (DX) fan coil systems, refrigerant flows directly through the coil to provide heating or cooling.
However, in chilled- or hot-water FCU systems, the fan coil unit does not use refrigerant; instead, it circulates chilled or heated water supplied by a central plant (such as a chiller or boiler