Fan Coil Units
Summary
Fan coil units are small air handlers with a fan, filter, and water coils, served by two-pipe or four-pipe chilled and hot water systems, in horizontal ceiling, vertical stacked, console, or concealed versions. They give individual room control with small pipes instead of large ducts, but condensate drainage, access for filters and valves, noise, and separate ventilation air must be designed in.
Cols
Terminology
- Two-pipe: one coil and pipe pair switched between chilled and hot water seasonally
- Four-pipe: separate cooling and heating coils for simultaneous heating and cooling
- Horizontal / vertical / console: ceiling-concealed, closet-stacked, or exposed under-window units
- Vertical stack fan coil: high-rise residential unit with integral risers
- ECM motor: electronically commutated, variable-speed fan motor
- Valve package: control valves, balancing valves, and isolation valves at the unit
- Drain pan: condensate pan under cooling coils
Standards
Ratings
- Capacity and sound vary with fan speed; select at medium speed for quiet rooms
- Condensate drains sloped to an approved disposal point, with secondary protection where overflow could damage finishes
Test standards
- AHRI 440: room fan-coil ratings
- UL 1995 / UL 60335-2-40: equipment safety
- ASHRAE 62.1: ventilation provided separately
Components
- Cabinet and fan: with ECM motor
- Coils: chilled water and hot water or electric heat
- Filter: MERV-rated filter
- Drain pan and condensate connections
- Valve packages and controls: thermostats and DDC or standalone controls
Detailing
- Provide ceiling access panels for filters, valves, and motors
- Slope condensate lines and provide secondary protection over finished spaces
- Supply ventilation air directly to rooms or to fan coil returns from a DOAS
- Insulate chilled water piping to prevent condensation
- Locate units away from beds and quiet seating for noise control
Uses
Specific uses
- Hotels and dormitories
- High-rise apartments and condominiums
- Offices with central chilled and hot water plants
- Schools and hospital patient rooms (with ventilation added)
- Renovations with limited ceiling space
Pros and cons
Pros
- Individual room control
- Small pipes instead of large ducts
- Four-pipe systems heat and cool at the same time
- Works with central plants and heat recovery chillers
Cons
- Maintenance in each room or ceiling
- Condensate risks above finished spaces
- Separate ventilation system required
- Fan noise near occupants
Manufacturing and cost
Construction
- Units built at the factory; hung or set; piped with valve packages and condensate lines
- Ducted to grilles in concealed installations
Main manufacturers and suppliers
Trade association: AHRI.
Sources
- University of Houston: 23 82 19 fan coil units master specification, https://www.uh.edu/facilities-services/departments/fpc/master-specs/23-82-19-fan-coil-units.pdf
- UpCodes: 2024 IMC Chapter 3 (condensate disposal), https://up.codes/viewer/department-of-defense/imc-2024/chapter/3/general-regulations
- AHRI: standards, https://www.ahrinet.org/
- Wikimedia Commons: Fan-Coil Unit.jpg, by Saud (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Fan-Coil_Unit.jpg