What is a fan coil unit? How it works, types and applications

A fan coil unit (FCU) is a device used to heat and cool indoor spaces as part of a water-based (hydronic) system. Unlike a refrigerant split system, a fan coil unit uses water as the heat-transfer medium — supplied by a boiler, heat pump or chiller. This makes it efficient, quiet and able to both heat in winter and cool in summer.

In this article we explain, in simple terms, what a fan coil unit is, how it works, the main types and how it differs from an air conditioner.

What is a fan coil unit in simple terms

A fan coil unit has two key parts: a heat exchanger (warm or chilled water flows through it) and a fan that draws room air across the heat exchanger. The air is heated or cooled and returned to the room.

If warm water flows through the coil, the room is heated; if chilled water (from a chiller) flows through it, the room is cooled. One unit covers both jobs year-round.

How a fan coil unit works

1. A pump supplies water to the unit’s heat exchanger.
2. A fan — in modern units an energy-efficient EC fan — pushes room air across the coil.
3. The air gives up or absorbs heat and is distributed back into the room.
4. A thermostat maintains the set temperature by adjusting fan speed and water flow.

When cooling, condensation forms on the coil, so fan coil units intended for cooling include a condensate drain pan.

Components of a fan coil unit

• Heat exchanger (copper–aluminium) — transfers heat between water and air;
• Fan (EC technology — efficient, quiet, smoothly adjustable);
• Filter — cleans the air;
• Condensate pan — when cooling;
• Casing — stainless steel on quality units;
• Controls (thermostat, valves, actuator).

2-pipe vs 4-pipe fan coil units

• 2-pipe — one supply and one return; the system delivers either warm or chilled water at a given time. Simpler and more economical.
• 4-pipe — separate heating and cooling circuits, allowing some rooms to be heated while others are cooled. More flexible, used in larger buildings.

Types of fan coil units

• Ducted fan coil units (DF) — concealed above a ceiling, air delivered through ductwork. → Ducted fan coils DF
• Cassette fan coil units (CF) — mounted in the ceiling, distributing air in several directions. → Cassette fan coils CF
• Wall-mounted fan coil units (HWF) — compact units mounted on the wall. → Wall-mounted fan coils HWF
• Trench (recessed-floor) fan coil units (FCH, FCHV) — recessed into the floor along glazing, staying out of sight. → Trench fan coils FCH

Chiller and fan coil systems

Fan coil units are often paired with a chiller: the chiller cools water that is pumped to fan coils throughout the building. This is an efficient solution for buildings with many rooms — hotels, offices — where cooling (and heating) is managed centrally.

Fan coil unit vs air conditioner

A domestic split system uses refrigerant and usually serves a single room. A fan coil unit runs on water and is part of the building’s overall system: one source (boiler, heat pump or chiller) feeds many units. This gives more even comfort, efficiency and flexibility in larger buildings.

Where fan coil units are used

Fan coil units are used in offices and administrative buildings, hotels, retail and public spaces, and in residential buildings — anywhere efficient heating and cooling from a water system is required.

How to choose a fan coil unit

Consider the required capacity (heating and cooling), noise level, mounting type (ducted, cassette, wall-mounted, trench) and whether the system is 2-pipe or 4-pipe. For projects, the availability of technical documentation and selection support matters. Need help selecting? Contact the Konveka export team.

Konveka fan coil units

Konveka is a European manufacturer of hydronic fan coils and convectors since 2005. Our fan coils use EC fans, have a stainless-steel casing and are tested to EN 442 and EN 16430. Products are supplied to distributors and projects in more than 30 countries. See the full range.

Frequently asked questions

What is a fan coil unit in simple terms? A device with a heat exchanger and a fan that heats or cools a room using water as the heat-transfer medium.

How is a fan coil unit different from a convector? A convector usually works by natural convection (no fan) and mostly for heating; a fan coil unit has a fan and can both heat and cool.

Do I need a chiller for a fan coil unit? For cooling you need a source of chilled water — a chiller. For heating, a boiler or heat pump is enough.

Can a fan coil unit be used for heating only? Yes. In a 2-pipe system with warm water it works as an efficient heating unit.