What Is an FCU — Fan Coil Unit?
The Founder's Explanation (Teach Exactly This Way)
"FCU — miniature of AHU — Fan + Coil. That is all."
Teaching the Concept
The AHU serves an entire floor from one central location. But individual rooms — a hotel bedroom, a hospital patient room, a private office cabin — need individual temperature control.
Cabin 301 occupant wants 22°C. Cabin 302 occupant wants 26°C. One AHU supply temperature cannot satisfy both.
The FCU — Fan Coil Unit — solves this. Installed in the ceiling void or wall of each individual room. Has exactly two parts:
FAN + COIL = FCUThe fan draws room air in and pushes it back out after conditioning.
The coil has chilled water flowing through it — room air gives up heat and comes out cool.
Each FCU has its own chilled water valve controlled by BMS. When room thermostat says warm — valve opens, chilled water flows, room cools. When temperature reaches setpoint — valve closes.
AHU vs FCU:
| Feature | AHU | FCU |
|---|---|---|
| Size | Large — plant room | Small — ceiling/wall |
| Serves | Entire floor or zone | Individual room |
| Fresh air | Yes | No — recirculates room air |
| Individual control | No | Yes — each room independent |
| Used in | Open offices, lobbies | Hotel rooms, cabins, wards |
Related Topics
- What is BMS integration? — how a BMS connects with VFDs, energy meters, BACnet/Modbus devices and other building systems
- How to design a BMS system step by step — the complete BMS design methodology covering site survey, IO list, controller selection, sequence of operations
- What is a Building Management System (BMS)? — fundamentals of BMS controls and architecture for HVAC, lighting, energy and access
- What is BMS commissioning? — the disciplined commissioning process that turns a BMS install into a working building brain
- Browse all HVAC Systems topics — more from this section of the EnSmart BMS Library