A refurbishment of the chillers serving the National Archives' repositories at Kew is ensuring that the nation's heritage is protected.
The National Archives' collection of over 11 million historical government and public records is one of the largest in the world. From Domesday Book to modern government papers and digital files, its collection includes paper and parchment, electronic records and websites, photographs, posters, maps, drawings and paintings.

The right environmental conditions in TNA's repositories at Kew are crucial to maintaining the nation's heritage for generations to come; unless temperature and humidity levels are strictly controlled, these important documents could suffer lasting damage.

Facilities management provider Ecovert FM's Special Projects Team is on hand to make sure conditions are spot on. 'Conditions are very tightly controlled in the repositories,' explains Ecovert FM's Kevin Skinner. 'We control space temperatures to 18 ± 1 deg C and humidity levels to 50 ±5 per cent.'
The team has recently carried out a full replacement of the chiller units supplying the older of The National Archives' two repositories: Q1. Three obsolete machines have been replaced by three units from Klima-Therm's Turbomiser range.

Turbomiser is the result of a joint development programme by UK companies Klima-Therm and Cool-Therm and Italian manufacturer Geoclima.

Terminal failure

'The original screw compressor chillers were some 15-20 years old. One had failed terminally and the spares are now difficult to obtain, plus they were inefficient in today's terms and also ran on R22 refrigerant,' says Kevin Skinner, explaining the need for the change.

The National Archives' specification called for chilled water at 2 deg C at certain times of the year for the repository's constant air volume and variable air volume air conditioning systems, while also maintaining water at 6 deg C to common area air handling units (AHUs). The 24/7 operation also demanded reliability and enhanced environmental credentials over the old system, both in terms of running costs and the refrigerant gases used.

'Ecovert FM worked with design consultant Ian Mackay Associates Ltd to develop the concept. We opted for Klima-Therm's Turbomiser chillers primarily for their efficiency and the proposed energy savings, but also for the company's professionalism, delivery times and speed of mobilisation,' says Kevin Skinner.

Three 910kW water-cooled Turbomiser models have been selected. Each chiller has three Danfoss Turbocor oil-free, variable speed centrifugal compressors, operating on a fully-flooded immersion type shell and tube evaporator.

Selection proved to be the easy part. The chillers' location in the lower ground floor plantroom at Kew gave the team a lot to think about. 'There were severe limitations because of the height, size and shape of the equipment and the space we were working with. These are effectively bespoke units that have been specially designed to fit,' recalls Kevin Skinner. The restricted plant room access meant that the compressors had to be removed from the chillers and lifted back on once in the plant room.

Preserving documents

This, of course, was only after the operation had been carried in reverse on the old chillers. The importance of preserving the documents meant there could be no loss of control of environmental conditions, so chilled water production had to be continuously maintained while the refurbishment was taking place.

'We removed the dead machine first and left the other two running,' says Kevin Skinner. 'Then we installed the first Turbomiser. Once that was up and running and online, we could remove the other two old machines while still maintaining the chilled water supply.'

Due to the obvious importance of humidity control at The National Archives, the BMS has been developed to determine the most beneficial instantaneous chilled water temperature for dehumidification within the archives. And the Turbomiser chillers have been specifically designed to operate on a variable chilled water output down to 2 deg C when the building requires lower water temperatures.

The new equipment has now been up and running since January this year and it has exceeded all expectations. The National Archives has monitored energy use for February and March 2011 against the previous year and found the Turbomisers to have brought about a 42 per cent reduction in running costs.

The client isn't the only one that is happy. 'I've been very impressed to date,' says Kevin Skinner. 'The system has performed exactly as Klima-Therm said it would. We have very little input at all. In fact, it takes a bit of getting used to the different sounds - these are just so much quieter and it really is impressive to see these units start off on just 5A of current. They just go about their business and can stop and start again an unlimited amount of times each day; just fantastic.'
There's no recommendation higher than repeat business of course. Ecovert FM has opted for the Turbomisers at Barnet Hospital, North Middlesex Hospital and installations at other Ecovert FM clients are under review by Kevin Skinner.

As well as supplying the chillers, Klima-Therm was also instrumental in the project as the installing design and build contractor. 'It has been a very tough and involving project, but ultimately very fulfilling,' comments Klima-Therm's Robert Boardman.

Tailored equipment

'We were always certain that this technology would meet our client's expectations; however we are delighted to have exceeded them. The bespoke nature of these machines enables us to very easily tailor equipment to our client's specific needs and the actual installation of the equipment was relatively straightforward.

'With the help of MEIT Associates, we also managed to successfully implement Ian Mackay's concept of variable chilled water temperature in a secondary water system designed for 6 deg C. The biggest challenge for us was maintaining water at 6 deg C to common area AHUs while still generating water at 2 deg C for the archives.'