Fan Coil Units

A fan-coil unit (FCU) (Fig. 26-5) is a factory-assembled unit with a heating and/or cooling coil, fan, and filter. Wall, ceiling, and vertical stacking models are available. Some designs are concealed in custom enclosures, semi-recessed into the wall, or installed as floor consoles with various cabinets. Recessed units are often found along corridors. Ceiling models are available in cabinets for exposed locations, or without a cabinet for concealed mounting. They should not be mounted above solid ceilings, as the condensate drains are prone to clogging and the drain pans can overflow, requiring maintenance. One ceiling unit can be ducted to supply several adjacent small spaces. Vertical stacking units are used in multiple-floor apartment buildings, condominiums, office buildings, and hotels. They eliminate the need for separate piping risers and runouts.

Fan-coil units may have one or two coils. Those with a single coil can only heat or cool without a seasonal changeover period, but the design saves plumbing costs.

Fan Coil Unit
Figure 26-5 Fan-coil unit (FCU).

Adding an electrical heating coil gives more versatility, and even with the electrical hookup and electricity for heat, is still less expensive than two-coil units. Units with cooling have condensate drip pans connected to drain lines. Units with a cooling coil also dehumidify. A single unit serves one or a small number of rooms. Baseboard, valance (above window), and corner FCUs are available.

Fan-coil units are a good choice for serving a large number of small, individually controlled rooms with a variety of occupants, such as hotels and motels, apartments, nursing homes, and medical centers. Since FCUs don't provide fresh air for ventilation, each space must have operable windows for ventilation. Maintenance occurs in the room, along with fan noise, and the drain pans may support bacterial growth. The filters on FCUs are relatively ineffective.

Unit ventilators are FCUs with an opening through the exterior wall for outside air. Unit ventilators offer individual temperature control in each room. They circulate only chilled or heated water from a central unit to the room. An inside damper controls the amount of fresh air. Room air plus a percentage of fresh outdoor air is filtered and passed by a heated or cooled water coil.

The opening through the wall is covered with a lou-vered grille, which may leak air. The result can be drafts, energy waste, and the possibility of freezing and rupturing coils. Circulation of cooled water causes condensate to form on the coil, as with other FCUs.

Unit ventilators are good for spaces with high-density occupancies and perimeter rooms without operating windows, like school classrooms, meeting rooms, and patient rooms in hospitals and nursing homes. With automatic controls and a motorized damper, unit ventilators can use an economizer cycle to save energy.

Because little air mixes between zones, FCUs provide isolation from potential air contaminants. They are easy systems to retrofit, and are often used in hotels, motels, or apartments. However, the use of all-water systems requires a lot of maintenance. Each FCU has filters that must be cleaned, and a drain pan to treat and empty. The noisy fan can provide masking noise, or may be objectionable.

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Responses

  • frances
    How to design fan coil?
    3 months ago

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