Advanced Air Air Fan Coils Chilled Beams News 040411

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ADVANCED AIR - Major Changes For Fan Coils And Chilled Beams

With the development of high efficiency fan coils the terminal air conditioning market is going through a major change. Andrew Sargent, General Manager Advanced Air, comments.

Since chilled beams were introduced to the UK market in the mid 1990’s their popularity has increased mainly at the expense of fan coil systems. It probably comes as no surprise to find out that the energy credentials of chilled beams were far superior to those of fan coils. Up until recently chilled beam manufacturers were able to demonstrate a 15% - 20% saving in total building carbon emissions compared to the conventional ac constant speed fan coil units.

With successive building regulations increasing the focus on carbon emissions chilled beams became very popular as indicated by our marketing figures given in Table 1.

Table 1
                                                Chilled             Fan
                                                Beams             Coils                VAV
£M
1997                                           1                    40                    10
2007                                          30                   30                    2

However fan coil manufacturers have now developed a new generation of highly efficient units which utilise the new technology in the form of ec motors. These motors have reduced average specific fan powers by factors in excess of 5 as per the graph in Figure 1. A further benefit of the ec motor is that you can vary the speed which gives variable air volume (VAV) and further significant savings in energy.

A further increase in the fan coil energy efficiency can be made by improving the fan deck design. Traditionally a vertically mounted centrifugal fan has been used, and to keep the fan coil height to a reasonable dimension so that it could easily fit into the ceiling void multiple small (low height) vertically mounted fans were used. The European ec fan deck has up to 5 motors each with their individual fan.

These fan decks are normally “bought in” by the fan coil manufacturer either from the motor supplier or another manufacturer. At Advanced Air we design and manufacture our own fan decks which means that we can adapt the fan configuration quite easily. We also have a strong working relationship with our American based ec motor manufacturer with full access to his R & D facilities. By combining the expertise of both companies we were able to develop a unique fan deck with only one fan horizontally mounted as per Figure 2. This innovation gave us a much lower SFP and a more efficient fan coil which neutralises the carbon emission argument between the two systems.

This has had a profound effect on the increased interest in these highly efficient fan coils because “deep down” if seems that the consultant prefers fan coils to chilled beams. There are of course compelling reasons to use ec/VAV fan coils instead of chilled beams and the main issues are:-

Unit Price/Installed Cost – here the fan coil wins easily with the unit cost comparison making fan coils up to half the price of chilled beams. When looking at installed costs there are still significant savings when utilising fan coils.

Spacial Flexibility – with spec office buildings forming a major part of the market, flexibility for the developer means that letting the space is much easier with fan coils if partitions are moved and the system needs some modification. This can easily be carried out in the ceiling void and the worst case would be blanking/moving/activating diffusers as required. With chilled beams it is a major problem to change them and partitions normally have to be erected in predetermined positions.

Heating – virtually all fan coils are supplied as 4 pipe heating and cooling units, chilled beams are normally supplied in cooling only with low level heating coming typically from trench heating which can add to the cost and reduce the letable space.

We are already seeing a major swing to fan coils and I believe the proportion of systems will rise from 60% 40% to 90% 10% in favour of ec VAV fan coils. Chilled beams will therefore have a very much reduced market size and will predominantly be the exposed multi service type of systems.