Fan coil units: types, capacities and where they fit
Updated 23 October 2026 · SEO Dons Editorial
What is a fan coil unit and how does it work?
A fan coil unit (FCU) is a fan and a water-to-air heat exchanger in one casing. CIBSE Journal says the fan draws air across a coil served by either low-temperature hot water or chilled water, and that the unit always includes a fan, at least one coil and some form of control, and normally a filter.
The retained ecodesign regulation (2016/2281) defines a fan coil unit as a device that provides forced circulation of indoor air but does not include the source of heating or cooling. That comes from a chiller or heat pump elsewhere, which the commercial chillers page covers. Water is piped to the room because, as CIBSE Journal notes, it needs significantly less space and transport energy than moving the same heating or cooling as air.
What types of fan coil unit are there?
CIBSE Journal lists horizontal units concealed in ceiling voids, horizontal units left exposed, units beneath raised floors, and vertical units for refurbishments and low ceilings. The table shows one UK manufacturer's published families as examples, not limits.
| Type | Where it sits | Published cooling range |
|---|---|---|
| Cassette (FWF-D) | Ceiling grid, 600 x 600 mm module | 1.3 to 5.1 kW |
| Concealed, medium pressure (FWQ-A) | Ceiling void, external static pressure up to 140 Pa | 2.1 to 11.5 kW |
| Concealed, high pressure (FWN-A) | Ceiling void, external static pressure up to 180 Pa | 2.7 to 17.6 kW |
| Floor-standing (FWV-D) | Floor, vertical mounting | 1 to 7.78 kW |
| Wall-mounted (FWT-GT) | Wall mounting; 2-pipe only in this range | 1.9 to 5.2 kW |
The ecodesign rules define rated cooling capacity as cooling at standard rating conditions, so compare like with like when reading two datasheets. Most of these ranges come in both 2-pipe and 4-pipe form, which the 2-pipe versus 4-pipe guide explains.
How big and how noisy is a fan coil unit?
One unit serves a small zone, so an office floor has many; the ranges above run from 1 to 17.6 kW of cooling per unit. The ecodesign regulation requires manufacturers to publish, from 1 January 2018, each fan coil unit's sensible and latent cooling capacity, total electric power input and sound power level at each speed setting. Ask for sound power by speed, because the speed the controller actually uses is what occupants hear. The chilled beams versus fan coil units page compares fan noise with the alternative.
CIBSE Journal says the casing is insulated to reduce noise transmission, acoustic lining may be added to the discharge, and modern units use EC DC motors that are easy to speed-control. Turndown is typically limited to no lower than 70% of design speed, to protect air distribution and avoid dumping cold air on occupants. One manufacturer credits the tangential fan in its wall unit for a low operating sound level.
What is the difference between a fan coil unit and an air handling unit?
CIBSE Journal calls an FCU, in effect, a compact air handling unit that would not normally humidify air. Unlike most AHUs, many FCUs supply no outdoor air and simply recirculate room air, so they are used with a central AHU that supplies ventilation air from outdoors. Some FCUs can draw outdoor air directly. The air handling unit guide covers the central side.
Where a unit cools and dehumidifies it makes condensate, so CIBSE says the coil should have a properly orientated condensate tray and proper condensate drainage.
Where does a fan coil system beat VRF?
A fan coil system carries heat and cold as water, VRF carries refrigerant, and the difference shows in refrigerant charge, comfort control and plant space. A 2022 CIBSE Journal study by Hoare Lea modelled three options for an eight-storey, 12,500 square metre office.
| Option | Modelled annual energy use | Whole-life carbon over 60 years |
|---|---|---|
| Four-pipe fan coils on air source heat pumps | 28.9 kWh per square metre | Lowest of the three |
| VRF (R410A) | 21.5 kWh per square metre | Highest of the three |
| Hybrid VRF (water to the floors) | 23.0 kWh per square metre | Between the two |
The fan coil option had the lowest whole-life carbon despite performing slightly worse in operation. The reason was refrigerant: the heat pump plant holds a much lower charge, and a standard R410A VRF installation could generate more than twice the emissions of a gas boiler system over 60 years. The article adds that water-based systems have historically given closer control of off-coil temperatures, and so of room comfort, although recent advances have narrowed the gap.
The trade-offs are real: VRF was the most efficient in operation, and the heat pump plant needed the most roof space. The VRF versus chiller comparison and the heat-recovery VRF guide cover the refrigerant side.
What drives the cost of a fan coil installation?
This page gives no prices, because no dated official price source was found for fan coil units. These items move a quote, and each is worth asking about separately.
- Number and size of units. Room count and heat gains decide it; the ranges above start at about 1 kW per unit.
- Two pipes or four. A second water circuit adds pipework and controls.
- Valves and controls. CIBSE says control valves are likely to come as part of the FCU package, and that FCUs are increasingly available with building management system connections.
- Condensate and filters. Some units include a drain pump, and one range lists G2 filters as standard with G3 and G4 as options.
- The plant behind them. The chiller or heat pump is a separate cost; the chiller cost guide explains what drives it.
How long do fan coil units last, and what maintenance do they need?
Maintenance is spread across many small units. CIBSE Journal says it needs a carefully considered procedure so that filters, condensate drip trays and pumps, control elements and other serviceable items are properly attended, with access planned at design stage. It records cases of FCUs installed above plastered ceilings, which prevented access without destroying the finished surfaces. The maintenance contract checklist covers what a contract should list.
For service life, the best public data found is ASHRAE's service life database, whose filters are US regions and states. It lists 2,884 fan coil units. Of those, 1,605 were still in service with a median age of 27 years, and 1,279 had been replaced, with a median age at replacement of 36.5 years. Read that as a US sample, not a UK design life: ASHRAE states the data are provided as is without warranty, and the age at which a unit was replaced is not necessarily the age at which it failed.
If you want help specifying fan coils with the chilled water plant behind them, the commercial chillers page explains the process, and you can send an enquiry through the site's form.
Sources
Regulations and guidance are revised, so confirm the current text before relying on a figure. Manufacturer ranges are examples from one maker, not a ranking.
- Module 101: The evolution of fan coils for efficient conditioning of room air, CIBSE Journal, posted September 2016; checked 22 October 2026.
- Module 252: Design considerations for fan coil units with low-temperature heat sources, CIBSE Journal, posted August 2025; checked 22 October 2026.
- Calculating whole life carbon in heating and cooling systems, CIBSE Journal, posted April 2022; checked 22 October 2026.
- Commission Regulation (EU) 2016/2281, article 1, legislation.gov.uk, revised 09/01/2017; checked 22 October 2026.
- Commission Regulation (EU) 2016/2281, article 2, legislation.gov.uk, revised 09/01/2017; checked 22 October 2026.
- Commission Regulation (EU) 2016/2281, annex II, legislation.gov.uk, revised 09/01/2017; checked 22 October 2026.
- FWF-D cassette fan coil, Daikin Applied UK, manufacturer's own page; checked 22 October 2026.
- FWQ-A concealed fan coil, Daikin Applied UK, manufacturer's own page; checked 22 October 2026.
- FWN-A concealed fan coil, Daikin Applied UK, manufacturer's own page; checked 22 October 2026.
- FWV-D floor standing fan coil, Daikin Applied UK, manufacturer's own page; checked 22 October 2026.
- FWT-GT wall mounted fan coil, Daikin Applied UK, manufacturer's own page; checked 22 October 2026.
- HVAC Service Life Database: air distribution, fan coil unit, ASHRAE Public Database, live database; checked 22 October 2026.
- ASHRAE Service Life and Maintenance Cost Database, ASHRAE Public Database, live database; checked 22 October 2026.
Common questions
Do fan coil units bring in fresh air?
Many do not. CIBSE Journal says many FCUs simply recirculate room air and work with a central air handling unit that supplies ventilation air. Some units can draw outdoor air directly.
Can fan coil units run from a heat pump?
Yes, but heating output falls at the lower water temperatures a heat pump produces. CIBSE Journal says some manufacturers now make heat pump-ready units. Ask for heating output at your design flow temperature.
Does a fan coil unit need a drain?
If it cools, it makes condensate, so it needs a tray and, where it dehumidifies, proper drainage according to CIBSE Journal. Some units include a drain pump, as in Daikin Applied UK's FWQ-A range.
Is a fan coil unit the same as a split system indoor unit?
No. A chilled-water fan coil is fed by pipework from central plant. CIBSE Journal says that when cooling comes from direct refrigerant, the unit becomes a split-type air conditioner in the VRF family.
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