The fan coil sound standards debate

Noise can so easily be misrepresented. For example, the ubiquitous "NR guide" has figures that could be based on room volumes ranging from 25 to 250 m3 and reverberation times from 0.2 to 1.2 s. The result of this is that a fan coil unit could be selected to provide an acceptable NR30, but actually do an un-acceptable NR40 because the guide is not specific enough about the variation of conditions found in real buildings. Here's how to avoid this scenario:

• Use equipment from a reputable manufacturer with the facility to recreate the actual environment that the unit will operate in - then test it to one of the current accredited standards - such as BS ISO 9614-1.

• The test should give separated return air and breakout measurements. This allows the acoustician to know whether fitting a return air silencer will actually affect the noise at all.

• Make sure that the noise is tested at the same time as the air flow, external pressure and thermal duty. If the fan was producing less air, or was operating against less pressure, the unit may well achieve the noise requirements while sacrificing the performance.

Julian Jowitt, Carrier Air Conditioning