Statistics from BSRIA show that the fan coil is still the most popular type of air conditioning terminal unit - but how has a product that has been around since the 1970s withstood competition from more modern products? Andrew Saxon tells us more
Since its introduction to the UK in the 1970s, the fan coil unit (FCU) has earned an enviable reputation and an excellent track record for providing reliable, cost-effective, flexible air conditioning throughout thousands of commercial buildings.
However, with the introduction of more modern products into the air conditioning sector, and an increased focus on energy efficiency, the FCU has had to move on.

The most notable threat for the FCU comes from the low-energy chilled beam. With chilled beams boasting low energy use and low carbon emissions, a few years ago there was a dramatic increase in the demand for this type of product.

By 2007 the chilled beam market had reached a value of around £30m, mostly at the expense of the traditional, less efficient FCU.

But in recent years we have seen a u-turn, with BSRIA figures indicating that the FCU market is now larger than the combined total for all other terminal unit products, including chilled beams. This turnaround is testament to the significant changes manufacturers have now made to FCUs.

Efficiency
FCUs were always cheaper than chilled beams as well as more flexible, as fan coil systems can be more easily modified to match a building's layout if the design should change and can also provide heat as well as cooling.

However, in terms of energy efficiency - which is of course a principal factor in the decision-making process because of the UK's carbon reduction commitments - in the past the FCU couldn't compete.

Today, the energy efficiency credentials of FCUs and chilled beams are much more even - due to the introduction of the electronically commutated (EC) motor.

EC motors have given FCUs a new lease of life, and recent research suggests that in terms of energy efficiency there's little difference between an EC FCU and a chilled beam system.

EC FCUs are more efficient than conventional alternating current (AC) FCUs. Importantly, the air volume can be more readily altered in line with cooling and heating demands, so the maximum design air volume/speed is only used when required.

Traditional FCUs provide a constant air volume, but in reality this isn't always needed.

Conditions are constantly changing throughout the day and year - varying weather patterns will affect the internal environment, as will any changes in occupancy or heat-generating office equipment such as PCs and printers, and any reconfiguration of space.

When manufactured with high efficiency EC fan motors, fan coils offer comparatively low energy consumption.

Claims suggest EC FCUs use up to 70% less energy than traditional products and that a specific fan power (SPF) of 0.3W/l/s or lower can be achieved (compared to an SPF of 0.7W/l/s for an AC FCU).

They will also operate for twice as long, resulting in lower maintenance costs.
Better still, EC FCUs can be coupled with intelligent controls, programmers and building management systems to optimise energy efficiency.

And EC motors are becoming even more efficient in line with the ErP Directive and Part L2 of the Building Regulations.

Since June 2011 IEC motors have needed an efficiency class of at least IE2 - with IEC motors of a lower efficiency class not being allowed to be marketed within the EU. From January 2013 fans sold within the EU have needed to comply with the ErP Directive for fans, and have to meet specific efficiency values.

Meanwhile Part L2A and Part L2B state that the SFP of an FCU should not exceed 0.8W/l/s when measured as the rating-weighted average of the installation. And when Part L2 is revised we're likely to see an SFP requirement of 0.4W/l/s.

Biddle of course welcomes the changes that are being made to the efficiency of the FCU, and the positive effect they are having on the market.

We do, however, have concerns that because the most energy efficient fan motors are more expensive, this could have serious implications for manufacturers, end-users and the environment.

Cost implications
For manufacturers, the cost implications are two-fold. Firstly, they will be buying a more expensive component, and secondly, because they are essentially adding a different technology to their product that will perform differently there will be costly modifications and testing/approval procedures to undertake.

Coil sizes have needed to change too, resulting in further costs for manufacturers.
Modern FCU products need to operate with lower-grade chilled water (10/14°C rather than 6/12°C) and hot water (60/40°C rather than 82/71°C). This has resulted in the introduction of larger coils to enable the FCU to effectively deliver its cooling and heating duties.

Manufacturers can choose to absorb these additional costs, but this will be difficult for those already working to very tight margins. In reality, the cost is more likely to be passed on to customers through product price increases.

The worry is that when faced with additional costs, customers looking to retrofit products will decide not to invest and will instead keep their old, inefficient air conditioning systems - so efficiency levels will not improve and carbon emission reduction targets will not be met.

Meanwhile, on new projects, the increased cost could be more easily built in, but equally, it might lead to customers deciding against the investment altogether.

We can of course talk about payback periods and how a more efficient fan motor will quickly pay for itself in terms of energy savings, but in many cases FCUs are bought by a landlord, who doesn't pay the energy bills and won't therefore see any monetary benefit.

In this scenario payback figures are essentially meaningless, as the property owner will usually only be interested in the capital cost of the equipment.
The FCU has continued to evolve, effectively protecting its position as the most popular type of air conditioning terminal unit in the UK.

With the requirements for fan motors becoming ever more stringent we predict that there are still changes ahead for FCU.

But while we understand energy efficiency improvements are necessary, the approach does need to be a sensible, balanced one that takes the added cost into consideration.

// The author is marketing manager at Biddle //