The National Archives can boast one of the biggest collections in the world with over 11 million historical documents. Proper temperature and humidity conditions within the depository in Kew are essential for the conservation of these documents.


The purpose was the replacement of former screw chillers with R22 with more efficient and reliable units. In some periods, there is the need to keep water temperature to 2 °C for air conditioning systems in the depositories and, at the same time, to keep water temperature to 6 °C for UTAs.


The project concerned three 910 kW Turbomiser TMH water cooled chillers, equipped with Danfoss Turbocor variable speed oil-free centrifugal compressors and total immersion evaporators.


The National Archives has confirmed that the new chillers are much more noiseless, reliable and stress proof. Moreover, the comparison between the consumption of former chillers and the one of the new plant has pointed out that Turbomiser units leads to a reduction of 42% in management costs.