The future for fan coil units looks positively healthy, thanks to their flexibility and cost savings advantages, says Joe Wieckowski, general manager of Colman Moducel
FAN coil units have been around for many years, are a trusted technology and a smart way of delivering locally conditioned air to a space that can be adjusted to suit requirements.

In recent years, they have come under attacks on all fronts and fallen out of favour. However, with a steady stream of new building projects coming through manufacturers are fighting back and showing the market for fan coil units is alive and kicking.

There is no disputing the facts. The fan coil market has suffered during the past few years. The market took a battering because of the popularity of VRV/VRF systems, over-supply of the market and competition from other cooling solutions such as chilled beams and ceilings and underfloor cooling and heating. Since then the market has held its own and is set to grow as more projects come to the fore.

According to statistics currently available (BSRIA) the UK fan coil market is valued at d44.4 million that represents in excess of some 64,000 units. To capitalise on this, manufacturers are upping their game, offering better engineered products underpinned by energy efficiency and playing to the many advantages that fan coil units can offer.

As their name implies fan coil units are relatively simple in their components. Fan coils are either two-pipe, cooling only, or four-pipe (accounts for 82% of the market), heating and cooling and offer good levels of comfort air conditioning. Traditionally, they have a secondary heating/cooling coil and forward curved double inlet centrifugal fans.

The fan coil unit is served by heating and/or cooling generated by a central plant and distributed in the form of low temperature hot water or chilled water. Their design is typically compact because of space restrictions in ceiling voids, where most units are situated, although many are wall mounted.

Benefits include:

· less construction space than systems requiring extensive ductwork;

· minimise air mixing from one unit to another;

· energy efficient - less than 0.8W/L;

· compact design;

· easy to maintain;

· no refrigerant pipework.

Fan coil units can be installed in a variety of positions, vertically, horizontally, in ceilings or below windows. Their flexibility makes them an excellent choice for individual or small rooms and to condition rooms with cooling or heating load characteristics that are different from surrounding rooms. Typical applications can include multi-tenanted buildings such as flats, student halls of residence and structures that have segregated spaces such as hotels, apartment buildings, hospitals (individual patient rooms), offices and other environments where temperature control is required in separated areas.

The hotel industry in particular has been quick to realise the potential benefits. Unoccupied hotel rooms can be kept at a set back temperature but quickly adjusted by reception as soon as a guest checks in and adjusted accordingly, by using the fan's high-speed outputs.

New build offices are also taking advantage of the benefits of being able to provide localised temperature control. A temperature of 23ºC might suit the majority of a building's occupants but there is always going to be someone who prefers a higher temperature.

Tremendous progress has been made. The design of fan coil units has come a long way in the last few years spurred on by demands for energy savings and the improvement in the design of temperature controls. Although VRF systems still have a sizeable chunk of the market, there is a steady move to fan coils systems that are being recognised by consultants and specifiers as a simpler and environmentally attractive alternative.

When it comes to the design of fan coils, size does matter. As a result, many manufacturers are constantly re-engineering systems to cater for the demand for airside control while still delivering high cooling duties and low noise ratings in a compact design.

Rotating drum damper arrangements as used in the Supreme A275 range remove the need for complex linkages and ensures that air leakage across the coils is very low. The tight seal achieved also means energy wastage is minimal.

Units are also becoming much slimmer to fit in the narrowest of ceiling voids while still providing full heating and cooling duties.

Some units such as the Excel W175 feature a slide-in coil section and drain tray assembly; the latter designed to be easily removed for cleaning at any time during a unit's life.

With so many points in its favour it is hard to understand why the take up in fan coils has been slow. There is no doubt that concerns over refrigerants and fresh air regulations have sparked off renewed interest and helped flag the benefits over traditional ahus, but for many there are still two overriding concerns: quality and noise.

Noise levels are a major concern. Levels as low as NR26 are achievable. Great strides have been taken by manufacturers to counteract noise issues by using better insulation and taking advantage of developments in fan technology. Fans can be adjusted to run at different speeds thus catering for variable noise levels. The larger and slower the fan the less noise is produced and energy usage is minimised.

Sustainability is also high on the agenda. Manufacturers are rationalising ranges and making every effort to use the latest components to provide high spec systems that meet energy savings requirements without compromising performance or reliability. EC motors are being used by many manufacturers.

Although more expensive, their energy saving benefits ensure that capital costs are recovered very quickly.

New building design and attitudes shaped and driven by energy considerations are providing many opportunities for fan coil and they could well gain in popularity at the expense of traditional HVAC systems.