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Fan Coil Units: The Perfect Solution for HVAC Systems

CEO Khai Intela
Fan coil units (FCUs), also known as Vertical Fan Coil-Units (VFCs), are essential devices in HVAC systems for residential, commercial, and industrial buildings. They consist of a heat exchanger (coil) and a fan, providing efficient...

Fan coil unit Fan coil unit

Fan coil units (FCUs), also known as Vertical Fan Coil-Units (VFCs), are essential devices in HVAC systems for residential, commercial, and industrial buildings. They consist of a heat exchanger (coil) and a fan, providing efficient temperature regulation for various spaces.

Why Choose Fan Coil Units?

FCUs offer several advantages over other cooling systems. Their simplicity, flexibility, and easy maintenance make them more cost-effective to install compared to ducted 100% fresh air systems or central heating systems. They come in different configurations and can be used in a wide range of applications, from small residential units to large commercial and industrial buildings.

Noise output from FCUs depends on the design of the unit and the building materials surrounding it. Some FCUs are designed to offer noise levels as low as NR25 or NC25, providing a comfortable and peaceful environment.

Design and Operation

Fan coil units can be classified into two main types: blow-through and draw-through. Blow-through units have fans fitted behind the heat exchanger, while draw-through units have fans fitted in front of the coil, drawing air through it. Draw-through units are considered thermally superior but are more expensive due to the chassis required to hold the fans.

FCUs can be either concealed or exposed within the room or area they serve. Exposed FCUs can be wall-mounted, freestanding, or ceiling-mounted, with appropriate enclosures to protect and conceal the unit. Concealed FCUs are typically installed within accessible ceiling voids or services zones and offer flexibility in locating return air grilles and supply air diffusers.

The coil in FCUs receives hot or cold water from a central plant and transfers heat to or from the air, depending on the desired temperature. The control of FCUs can be managed by a local digital controller, outstation, or a Building Energy Management System (BEMS), allowing centralized control and adjustment.

Hydronic Fan Coil Units

Hydronic fan coil units use hot or cold water to condition a space, with two main types: two-pipe and four-pipe units. Two-pipe units have one supply and one return pipe, while four-pipe units have two supply and two return pipes, allowing simultaneous heating and cooling. The piping networks connecting FCUs can follow different topology designs, such as "direct return," "reverse return," or "series decoupled."

Depending on the selected chilled water temperatures and relative humidity, the cooling coil in FCUs may dehumidify the air stream, producing condensate that needs to be drained. FCUs have purpose-designed drip trays with drain connections, which can be connected to a network of pipework or use a condensate pump in limited space scenarios.

DC/EC Motor Powered Units

DC (direct current) or EC (electronically commutated) motors are becoming increasingly popular in fan coil units due to their improved energy efficiency levels. These motors allow for precise control of fan speed through a 0-10 Volt input control signal. DC Fan Coil Units can significantly reduce electrical consumption, and when combined with occupancy and demand-based fan speed control, savings can reach up to 80%.

Areas of Use

In high-rise buildings, fan coils can be vertically stacked, interconnected by the same piping loop, and serve multiple floors. Fan coil units are particularly effective in hydronic chiller boiler systems for large residential and light commercial applications. They can be mounted in bathroom ceilings, providing unlimited comfort zones and energy-saving capabilities by turning off unused areas of a structure.

Installation

In high-rise residential construction, each fan coil unit requires a rectangular through-penetration in the concrete slab it sits on. Typically, 2 or 4 pipes made of ABS, steel, or copper go through the floor, insulated with refrigeration insulation. This insulation prevents condensate formation on chilled water lines.

Unit Ventilator

A unit ventilator is a type of fan coil unit commonly used in classrooms, hotels, apartments, and condominiums. It uses a fan to blow outside air across a coil, conditioning and ventilating the space it serves.

The European Market

The European market for fan coil units consists of various types, with 2-pipe and 4-pipe units being the most common. These units are sold with or without casing, as cassettes or ducted units. The market distribution by region varies, with Italy having the highest sales volume.

Fan coil unit

Fan coil units are a reliable and efficient solution for HVAC systems in diverse environments. Their versatility, ease of maintenance, and energy-saving capabilities make them an excellent choice for temperature regulation in both residential and commercial buildings.

References

  1. ASHRAE Handbook "2008 Systems & Equipment", Chapter 12.
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