What is FCU? FCU Maintenance Steps

FCU (Fan Coil Unit) is one of the commonly used air handling units applied in various areas of life, from residential to commercial and industrial sectors. So, what is FCU – Fan Coil Unit? What is its structure and operating principle? What are the technical requirements when installing FCU? Let’s find out with INTECH Service in the following article!

What is FCU – Fan Coil Unit?

FCU is short for “Fan Coil Unit”. FCU is a device used in HVAC (Heating, Ventilation, and Air Conditioning) systems. FCU is commonly installed in apartments, high-rise buildings, commercial buildings, supermarkets, hotels, restaurants, hospitals, etc., to regulate temperature and supply cold or hot air into a space.

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Although FCU is an air handling unit, its capacity is very modest, ranging from only 2kW to 20kW.

Structure of FCU

A Fan Coil Unit (FCU) has the following basic components:



Dust filter


Heat exchange coil

Condensation tray

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Classification of FCU

Wall-mounted FCU, ducted FCU, ceiling-mounted FCU

Wall-mounted FCU is directly mounted on the wall of a room or space. It is usually placed high on the wall and blows air into the space from the front or bottom.

Ducted FCU is installed directly through the wall, with part of the unit in one room and the remainder in another room.

Ceiling-mounted FCU is installed on the ceiling of a room or space.It can be ceiling-mounted or ceiling-hung to distribute air evenly from above.

These types of FCUs often have suitable casings to protect and conceal the fan coil unit along with the temperature control grille and air diffuser. Everything is enclosed in the casing while still ensuring the air distribution process.

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Ducted ceiling FCU, wall-concealed FCU, ceiling-concealed FCU

For concealed FCUs, they are typically installed within the void of the ceiling or suspended ceiling.

The devices are usually placed in the ceiling, leading to the fan coil unit, including the air cooling grille and air diffuser.

This type of FCU is used to utilize the c  eiling void to facilitate air circulation in the installation space.

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Cassette type FCU, 4-way blow cassette type, 1-way blow cassette type

Cassette type FCU blows air in a circular shape and typically has a central hole from which air is blown and distributed downwards. This type of FCU is often installed on the ceiling of a room or space.

4-way blow cassette FCU is typically square in shape and has the ability to blow air out from four directions, creating a four-way air distribution pattern. This ensures that the air is distributed evenly and comfortably in the space.

1-way blow cassette FCU is another type of Cassette FCU, usually rectangular or square in shape, and only blows air out from one direction. Typically, air is blown out from one side or a specific corner of the FCU.

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Operating Principle of FCU

From the central air conditioning, the coil will sense hot or cold water vapor and proceed to remove or add heat to the air through heat transfer.

Cassette type FCUs, whether 4-way or 1-way, are designed based on the type of fan used.

When the coil senses hot or cold water vapor from the central air conditioning, it will proceed to remove or add heat to the air through heat transfer.

Next, the units of the traditional fan coil will contain a heat stabilizer inside or may have been wired to operate together with a remote control unit.

We can also control the speed of the fan motor in the FCU to heat or cool as desired.

Additionally, some FCUs are equipped with permanently adjustable motors to adjust the levels within the coil to set the levels according to the desired simplicity, allowing users to adjust the fan speed themselves.

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Maintenance Steps for FCU

After a period of use, FCU maintenance is essential to ensure efficient operation and prolong the lifespan of the FCU. Typically, FCU maintenance will include the following activities:

Maintaining chamber and heat exchange coil.

Maintaining fan, valves, ducts, air supply, insulation.

Maintaining control systems, sensors, etc.

Details of FCU maintenance steps are as follows:

Step 1: Measure fan current, air velocity, and air temperature before cleaning FCU.

Step 2: Turn off the power to the FCU to ensure safety for both personnel and equipment.

Step 3: Maintain and clean the fan blades when removed from the FCU. Also, clean the dust filter, check the fan motor. Use high-pressure water to clean the evaporator coil. Drain water and clean residual water in the FCU to ensure the drain line is clear. Clean the return air grille and supply air grille of the FCU.

Step 4: Check overall components before restarting the FCU.

Step 5: Turn on the FCU power, check for leaks in the valves and seal with silver glue if any. Measure air velocity, current values, and temperature.

Step 6: Proceed with maintenance form and end the process.


Turn off the power before performing FCU maintenance.

Use appropriate protective equipment and tools.

Record all technical specifications and the condition of the FCU after maintenance.

It is advisable to use professional FCU maintenance services to ensure quality.

The above information provides insights into the structure, operating principles, and maintenance steps of FCU, hoping to help you understand this equipment better. With years of experience in the field, INTECH Service confidently provides HVAC system maintenance services. If you have any questions or need advice, feel free to contact us for support from our experts.