A fan coil unit (FCU) is a simple HVAC terminal unit made up of a fan and one or more heating and/or cooling coils, with a filter and controls, in one cabinet. The fan draws room air across the coil, which is fed with chilled water, hot water or refrigerant from a central plant, and blows the conditioned air back into the space. FCUs serve a single room or zone and are common in hotels, apartments, offices and schools.
Main parts
- Fan and motor – multi-speed or variable-speed (often EC motors).
- Coil(s) – cooling, heating or both; some units use an electric heating element instead of a hot water coil.
- Control valve(s) – modulate or open/close water flow to the coil.
- Filter – cleans the recirculated air.
- Drain pan and condensate drain – collect water from the cooling coil.
- Controls – a room thermostat or controller, often tied into the building automation system.
2-pipe vs 4-pipe fan coils
| 2-pipe | 4-pipe | |
|---|---|---|
| Piping | One supply and one return, carrying either chilled or hot water | Separate chilled and hot water supply and return |
| Heating and cooling | One mode at a time for the whole system (seasonal changeover) | Any unit can heat or cool at any time |
| Cost | Lower | Higher, more piping and valves |
| Comfort | Can struggle in shoulder seasons | Best zone control |
Common configurations
- Horizontal concealed, above the ceiling and ducted to diffusers
- Vertical floor or wall-mounted cabinet (console) units
- Ceiling cassette units
- Vertical stacked units with integral risers, common in high-rise hotels and residential
Fan coil unit vs air handling unit
An air handling unit is larger, usually central, and conditions outdoor air as well as return air for many zones through ductwork. A fan coil unit mainly recirculates air in one room or zone. In fan coil buildings, ventilation air usually comes from a separate dedicated outdoor air system or energy recovery ventilator, ducted into the space or to the FCU return.
Installation and maintenance tips
- Provide an access panel big enough to change filters and service valves, motor and drain pan.
- Slope the condensate drain, trap it where the manufacturer requires, and provide a secondary drain pan or overflow switch where needed.
- Flush the piping before connecting the coils, and insulate chilled water piping and valves to prevent condensation.
- Check fan noise at the speeds the units will actually run, and balance water flow during commissioning.
Related terms
Related templates and guides
- Introduction to Mechanical and Electrical Systems
- HVAC Design Quality Checklist
- General Details – HVAC Systems
Frequently asked questions
What does a fan coil unit do?
It heats or cools a single room or zone. The fan pulls room air through a filter and across a coil supplied with chilled or hot water (or refrigerant), then delivers the conditioned air back to the space, controlled by a local thermostat.
Is a fan coil unit the same as an AC unit?
Not exactly. A commercial fan coil unit has no compressor of its own; it relies on chilled and hot water from a central plant. In homes, the indoor section of a split air conditioner or heat pump is sometimes also called a fan coil, because it is a fan blowing across a coil.
What is the difference between an AHU and an FCU?
An AHU is a larger central unit that usually brings in and conditions outdoor air and serves several zones through ductwork. An FCU is a small local unit that mostly recirculates air in one room or zone. Many buildings use both: an AHU or DOAS for ventilation and FCUs for zone temperature.
Do fan coil units provide fresh air?
Usually not on their own. Most FCUs recirculate room air. Fresh air is supplied by a separate ventilation system, either ducted directly to the space or connected to the FCU’s return so the unit conditions it before supplying it.
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