KEEPING THE FANS HAPPY
07/03/2007
Although chilled beams are grabbing a bigger share of the comfort air conditioning sector, fan coil units have been the first choice for developers of large City-based office blocks for decades. Terry Farthing, Head of Communications at TROX UK, gives his thoughts on the system and its future.
The ubiquitous fan coil unit is something of a Cinderella system – out of sight and out of mind. However, taking it for granted could leave you severely out of pocket.
Fan coils are a well established terminal system for controlling room temperature. Most are installed in ceiling voids with flexible or rigid ducting serving a number of terminal outlets in the form of slot, swirl or louvre face diffusers. However, most of the time, these separate components are sourced from different manufacturers.
Recent market research conducted by TROX suggests that 53 per cent of consultants in the UK have had noise problems with fan coil units. The same research found that for any major project, 79 per cent of consultants would require a mock-up test before specifying particular products. Such a test carried out at BSRIA could cost £15,000 to £20,000.
TROX has addressed these problems by implementing a system engineering approach. This means that fan coil units and diffusers are provided from a single source, with guaranteed noise levels, thermal performance and air distribution.
In a bid to demolish the scepticism associated with the over-optimistic claims made by some fan coil unit manufacturers (BSRIA says it has found that some fan coil units it has tested had the performance which was 25 to 30 per cent down on catalogue data), TROX has invested £150,000 in a dedicated fan coil unit test chamber and a further two air distribution test cells at its Thetford, Norfolk, factory.
Accurate fan coil unit testing can demonstrate that equipment will do precisely what is claimed, minimising risks on projects and offering peace of mind to the client as well as helping TROX to develop the best solutions for particular projects.
TROX is the only manufacturer with a test facility that complies with the tough demands of BS4856 Part 1 1972 “Methods for Testing and Rating Fan Coil Units, Unit Heaters and Unit Coolers”, and Eurovent 6/3-1996 “Thermal Test Method for Fan Coil Units”.
The chamber can test thermal output and air volume performance of four-pipe fan coils with cooling and heating capacities of up to 6kW, and airflow rates between 50 and 500 l/s. Both horizontal and vertical units (with or without ducting) can be tested.
Future Issues
Airside fan coil units are very popular and account for around a quarter of the UK market with two basic designs available. The inlet or outlet damper options utilise an arrangement of dampers / flaps to divert air through heating, by-pass and cooling zones to control the temperature output.
The carry over or potential energy loss with some airside fan coils can be in excess of 500 watts in the bypass position. The new airside fan coils developed by TROX significantly reduce this energy loss and in general operation could be claimed to be negligible and also meeting the new Part L requirements.
There is however opinions in the market place that suggest airside units will reduce in popularity in favour of waterside units.
Another new development being pioneered by TROX is the use of waterside variable air volume fan coil units (VAV/FCU). Up until now fan coils have been constant speed, constant air volume. In other words the fan in the unit is on full speed all day irrespective of cooling/heating requirements. By utilising a variable air volume fan coil system (VAV/FCU) the motor speed can be varied by the building management system. Only a small speed reduction of 20% would cut in half the energy consumption from the fan motor. On a building of 10,000 m² with 400 fan coils this could equate to an energy saving of £15,000 to £20,000 per annum.
With the development of these energy saving ideas fan coils could hold on to its current market share. However there are compelling arguments for chilled beams so it will be interesting to see what happens over the next two years!
Market Facts & Figures
