# Fan Coil Unit [FCU]

> What a fan coil unit (FCU) is, its main parts, 2-pipe vs 4-pipe systems, common configurations, how it differs from an AHU, and installation tips.

- URL: https://essential.construction/academy/glossary/fan-coil-unit/
- Author: Kyle Parry (https://essential.construction/about-us/kyle-parry/, https://www.linkedin.com/in/kyleparry/) - Kyle Parry is the founder of Essential Construction. He has worked in construction for more than 20 years, leading projects across Canada for the country's largest contractors and developers.
- Publisher: Essential Construction (https://essential.construction/)
- Last updated: 2026-11-03

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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](https://essential.construction/academy/glossary/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](https://essential.construction/academy/glossary/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

- [Air Handling Unit (AHU)](https://essential.construction/academy/glossary/air-handling-unit/)
- [Heat Pump](https://essential.construction/academy/glossary/heat-pump/)
- [Variable Frequency Drive (VFD)](https://essential.construction/academy/glossary/variable-frequency-drive/)
- [Ductwork](https://essential.construction/academy/glossary/ductwork/)

## Related templates and guides

- [Introduction to Mechanical and Electrical Systems](https://essential.construction/academy/tutorials/introduction-to-mechanical-and-electrical-systems/)
- [HVAC Design Quality Checklist](https://essential.construction/files/construction/quality/hvac-design-quality-checklist/)
- [General Details - HVAC Systems](https://essential.construction/files/design/autocad/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.