Fan Coil Units
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Fan Coil Units
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Types of Fan Coil Units:

There are three main types of overall fan coil units.  These are:

  1. Fan coil unit with supplementary air
  2. Water distribution, 2-pipe
  3. Water distribution, 4-pipe


Fan Coils with Supplementary Air:

According to Mechanical and Electrical Equipment for Buildings (EMEB), a Fan Coil Unit (with supplementary air) is a “below-window unit…which moves the room air as it provides either heating or cooling.  Centrally conditioned, tempered fresh air is brought to the space in a constant-volume stream; the fan moves both fresh and room air across a coil that either heats or cools the air, as required.”  In addition, Fan Coil Units have a flexible installation, and may be located in arrangements other than below-window, as required.

2-pipe systems:

A 2-pipe system allows for either heating or cooling.  One pipe is for supply water, and the other pipe is for return.  Therefore, only hot or cold water can be distributed at any given time. (EMEB)

4-pipe systems:

A 4-pipe system allows for heating and cooling to take place at the same time in different locations.  With a supply pipe and a return pipe for hot water, and a second set for cold water, the 4-pipe system provides greater flexibility of control. 

A 4-pipe system may also contain 2 coils, if heating and cooling are required within the same unit at a given time.

Fan Coil Unit Components: (data from either EMEB, or The Architect’s Studio Companion)

  1. Coils

  2. Fans with motors

  3. Air Filter

  4. Controls (either a wall thermostat, or an on-box thermostat)

  5. Piping (return and supply)

  6. Condensate drainage piping

  7. Outside air grills

Types of Installation:

Fan Coil Units may be installed in a variety of positions.  A sample of these include: (see for more examples)

  1. Vertical

  2. Horizontal

  3. Ceiling installation

  4. Below-window placement

These installation options allow for a variety of placements within a structure. 

Typical Uses:

Fan Coil Units are a good choice for structures that have rigidly separated spaces.  These include:

  1. Dorms

  2. Hotels/Motels

  3. Apartment Buildings

  4. Hospital standard patient rooms

Places where a Fan Coil would not be advantageous:

Buildings that have adjustable space arrangements.
Buildings that are required to meet higher filter standards, including:

  1. Hospital Isolation Rooms

  2. Laboratories


  1. An advantage of the 4-pipe system is that it allows control of individual spaces.

  2. Fan Coil Units require less construction space than systems that require ductwork. (ASC)

  3. Fan Coil Units allow for very little air mixing from one unit to another, which is a benefit where air contamination is a concern. (EMEB)


  1. One of the biggest disadvantages of fan coil units is the issue of maintenance.  The filters require regular cleaning, and the pans require regular emptying. 

  2. A disadvantage to the 2-pipe system is that the system runs only hot or cold, and one person controls that.

  3. A Fan Coil Unit does not adequately control humidity.

Numeric Parameters:

Sizing parameters: (data from The Architect’s Studio Companion, p. 152)

  1. Height ranges: 25-28”

  2. Length Ranges: 30-84”

  3. Depth Ranges: 9-12"

As an example of technical numeric data for a Fan Coil unit, the following charts were taken from :

Technical Data:

Cooling Performance Data:

Heating Performance Data: