The big take over by chilled beams has not materialised, but fan coil champions still need to work hard to maintain their healthy market position, says David Fitzpatrick.
Fan coils continue to be specified in large numbers by consulting engineers. Some years ago it seemed that chilled beams were poised to grab significant market share, but the fact that fan coils offer greater flexibility and are a tried and tested solution means they remain the option of choice for many design engineers - particularly where high outputs are required.

However, the formulas used to calculate compliance with Part L (of the 2010 Building Regulations) favour the refrigerant-based systems, such as variable refrigerant flow (VRF) packages and, as a result, more of these are being installed in large commercial projects. New variations on the VRF theme, involving innovations like multiple condensers and zoning, have allowed them to upscale to buildings that were formerly almost exclusively served by fan coils or other water-based systems.

However, fan coils are not going away and it is not hard to engineer a system to meet the requirements of Part L (2010). Many design teams remain dubious about including too much refrigerant in a building so are steering back towards a more traditional approach. Fan coils that include only minimal amounts of refrigerant gas are, therefore, particularly attractive. It might be easier to hand the whole project over to a VRF design team, but often clients are looking for a flexible approach that can be more closely matched to a particular building's characteristics and layout.

Fan coils are also easier to apply to retrofit projects and do not require the same stringent maintenance regimes as refrigerant-based solutions.

The DC motors used at the quality end of the fan coil market have also cut energy consumption by up to 50 per cent compared with the AC motors of previous models - so are ideal for meeting Part L design constraints. Quality fan coils also come complete with variable fan speed control to further reduce energy consumption and this can increase energy savings to as much as 80 per cent.

It is also increasingly common for fan coils to be specified as part of a packaged solution. This should include the latest control technology, with highly accurate temperature measurement, to maintain operating efficiency of a complete system including fan coils, chillers, boilers, air handling units and pumps. Damper motors should also be fully modulating. Many systems are now being powered by heat pumps or other renewable sources giving an even more impressive low carbon profile to the system.

The manufacturers' professional body HEVAC has already helped to produce best practice guidance for consultants and contractors (CIBSE TM43) showing how system components can best be configured to deliver the ideal operating outcome. Later this year, the association will produce a briefer 'checklist' version so designers can easily compare the fan coil approach with possible alternatives.

Expensive mistake

Fan coils regularly face criticism for being too noisy, but often that is down to poor specification, inappropriate siting of a unit and - increasingly - a failure to carry out proper testing. Installing a system without testing it first is an expensive mistake as unpleasant surprises will only become apparent when the system is already on site and it is more difficult to put things right. Acoustic testing should be a pre-requisite for any fan coil system design and, although market conditions are very tough, skipping the test phase is a false economy.

In many cases, projects are won on price because the contractor looks to specify the smallest possible unit to meet the target indoor conditions. However, unless they take acoustic performance into account that unit may not achieve acceptable noise levels and a larger unit would be more appropriate. At Ruskin, we pride ourselves on our ability to produce sound power data for every unit under all conceivable operating conditions and at all fan speeds. Many consultants complain that this kind of comprehensive and verifiable sound data is now generally difficult to find.

Fan coils should not be regarded as a 'cheap option' - in many cases, it will be hard to differentiate the opposing approaches on price. Low noise, low global warming impact (GWP) and greater flexibility are better reasons for specifying fan coils than price. There is also a huge quality divide in the marketplace and specifiers should not sacrifice product quality, even in the particularly tough trading conditions we are all experiencing, because that will only lead to expensive problems further down the line.

The sophisticated VRF-type solutions available to specifiers have much to offer - not least the promise of a complete solution from a 'one-stop-shop'. However, there is no reason why multiple component suppliers cannot match or surpass the performance curves delivered by single solution providers.

At Ruskin, we have benefitted from the fact that we can supply fan coils in tandem with grilles and diffusers from within our group. This allows us to closely match the specification of the fan coil to air terminal devices to ensure the end client gets a solution that meets the needs of their building and delivers good indoor air quality.

Fan coils will continue to play a major role in the UK commercial air distribution market because, in this case, one size most certainly does not fit all.

• David Fitzpatrick is sales and marketing director of Ruskin Air Management