1️⃣ Can a Fan Coil Unit (FCU) Cool or Heat on Its Own?
❌ No! A Fan Coil Unit (FCU) does NOT generate cooling or heating by itself.
✔️ Instead, it acts as a heat transfer device that delivers hot or cold air to indoor spaces.
The performance of an FCU is measured in cooling capacity (kW) and heating capacity (kW), which depends on:
✅ Material quality of the heat exchanger (copper tubes, aluminum fins).
✅ Efficiency of the fan motor in circulating air.
✅ Temperature of the chilled/hot water supplied from the main system.
2️⃣ Components of a Fan Coil Unit
🔷 Fan: Circulates indoor air by blowing it across the coil.
🔷 Coil (Heat Exchanger): Contains chilled water (for cooling) or hot water (for heating).
🔷 Copper Tubes (Heat Transfer Medium):
- Thin-walled (0.25mm thickness) copper tubes allow efficient heat exchange.
- Water inside the tubes absorbs or releases heat to maintain the desired room temperature.
3️⃣ How Does an FCU Provide Cooling?
✔️ Chilled water (7°C – 12°C) from a chiller or heat pump is supplied to the FCU.
✔️ As warm indoor air passes over the cold coil, heat is transferred from the air to the water inside the coil.
✔️ The air temperature drops, and the fan blows cool air into the room.
✔️ The warmed water (now ~12°C) is returned to the chiller for re-cooling.
✔️ This continuous loop maintains cooling in the space.
🔵 Cooling Cycle Summary:
1️⃣ Chilled water (7°C) enters the coil → Heat from room air is absorbed → Water temperature increases (~12°C)
2️⃣ Fan blows the cooled air into the room
3️⃣ Warmed water returns to the main system for re-cooling
4️⃣ How Does an FCU Provide Heating?
✔️ Hot water (40°C – 60°C) from a boiler or heat pump is supplied to the FCU.
✔️ As cold indoor air passes over the hot coil, heat is transferred from the water to the air.
✔️ The air temperature rises, and the fan blows warm air into the room.
✔️ The cooled water (~35°C – 45°C) is returned to the heat source for reheating.
✔️ This continuous loop maintains heating in the space.
🔴 Heating Cycle Summary:
1️⃣ Hot water (50°C) enters the coil → Heat is transferred to the air → Water temperature drops (~40°C)
2️⃣ Fan blows the heated air into the room
3️⃣ Cooled water returns to the main system for reheating
5️⃣ Where Does the Chilled/Hot Water Come From?
✔️ A heat pump, chiller, or boiler supplies the chilled or hot water to the FCU.
✔️ The water circulates through pipes to each FCU unit in the building.
✔️ The FCU does not generate heat or cold air itself—it only distributes the conditioned air!
Key Sources of Chilled/Hot Water:
✅ Air Source Heat Pump
✅ Water Source Heat Pump
✅ Chiller (Cooling Only)
✅ Boiler (Heating Only)
6️⃣ Conclusion
✔️ A Fan Coil Unit (FCU) does not produce cold or hot air; it only transfers heat using chilled or hot water supplied by the main system.
✔️ The fan circulates air across the heat exchanger (coil) to cool or heat the room.
✔️ The efficiency of an FCU depends on the quality of the coil, fan, and water supply temperature.
✔️ Continuous circulation of water ensures stable indoor temperatures for comfort and efficiency.
✅ Now you know how FCUs provide cooling and heating! 😃