Advanced Air in Thetford, Norfolk has introduced a new fan coil unit. And it could be set to turn the market on its head - or at least on its side.
The energy efficiency (and hence carbon emissions) of fan coils is heavily influenced by the specific fan power SFP - the lower the SFP the more efficient the fan coil.
Advanced Air has launched new fan coil units known as the EPIC range. It claims the most energy efficient fan coils with average SFP down to 0.15 Watts per litre per second (w/l/s), a factor of nearly six below the SFP of 0.8W/l/s in the 2006 Part L Building Regulations.
The company has its technical centre and manufacturing base in Thetford, Norfolk, and it is there that it has developed what Andrew Sargent, general manager, claims as 'probably the most efficient fan coil in the world'.
The fan deck configuration is different from the normal one. Advanced Air has turned the fan deck on its side, or to be more technically correct the fan unit is mounted horizontally. This allows a much larger motor and fan impeller to be used and in most of Advanced Air's fan coils there is only one fan compared with the three to five fans currently used by manufacturers of conventional fan coil units. Advanced Air's engineers design and assemble the fans as opposed to the current trend in the UK of acquiring the fan deck from third parties.
Figure 1
This means the EPIC unit has a fan assembly where the motor impeller and fan scroll have been matched to give the most energy efficient solution as opposed to utilising a standard fan deck 'off the shelf'. This larger fan rather than multiple smaller fans in standard decks is the secret of the EPIC's superb energy credentials.
More to the point, Advanced Air claims it is cheaper than the equivalent EC fan coils currently available.
'Until recently in the UK, there has been only one supplier of EC motors,' says Mick Holland, Advanced Air's technical product manager. 'The solution was to use small EC motors with one motor per fan which is relatively expensive. Advanced Air sources its motors from the USA and with the parent company's, Nailor Industries, purchasing power, we can produce a very competitive product.'
Returning to the energy credentials (Fig 1), a comparison of the various fan coil types and their respective SFP is given and, as will be seen, the EPIC unit at 0.2 is way out in front. So how then does Advanced Air get to an SFP of 0.15? For the last 40 years virtually all fan coils have been constant fan speed and consequently constant air volume (CAV). Any changes in cooling or heating were adjusted by the water valve, ie varying the water volume.
Figure 2
However with the fans running at full speed all of the time this is a needless waste of energy.
By varying the air volume, significant reductions in energy can be achieved and typical values for a wide range of constant and VAV fan coils is shown in the energy comparison graph (fig 2).
The control philosophy is relatively simple (see fig 3). At maximum cooling the fan is running at 100% with the water valve fully open. As the cooling load reduces the fan air volume is reduced down to a minimum of 60%. If the cooling load reduces further the water valve is progressively closed until the dead band is reached. In other words the fan air volume is reduced first followed by a progressive reduction in the water cooling volume.
Figure 3
On heating the early morning boost has maximum air volume and heating. On the heating cycle the air volume is kept constant to ensure there is no stratification within the room. The heating requirement is usually a short period just before the building is occupied and therefore does not significantly impact on the carbon emissions.
It would be interesting to see how the market reacts to this new product development. According to Sargent, Nailor Industries in the States is selling more than 20,000 fan coils per year.
18 February 2010