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Office chillers cut costs on the south coast

An unusual form of air-conditioning is making its mark on an office in Southampton.

The offices of financial firm Skandia were originally cooled by two 1,000 kW chillers. However, the company looked to replace these following problems with the previous installation. Skandia selected Turbomiser chillers, manufactured by Italian firm Geoclima and supplied by UK distributor Cool-Therm.

One of the existing units was a free-cooling chiller, requiring the building’s entire chilled water system to be filled with 25 per cent glycol to minimise the risk of freezing. This required in excess of 20,000 litres of glycol.

The replacement chillers have centrifugal compressors that operate in a magnetic field, which the manufacturer claims makes them very low maintenance.

Cool-Therm managing director Ken Strong explains how the chillers work. “It’s based around the turbocompressor. A turbocompressor on its own isn’t any good though; you have to build a chiller around it.”

A Turbomiser combines that compressor with an immersion-style evaporator. “It’s different in that the refrigerant is in the heat exchanger shell and the water runs through the tubes inside that shell. We call it an immersion evaporator as all the tubes are immersed in refrigerant,” he says.

This is the opposite of a conventional chiller, which works on the principle that tubes of refrigerant run through a store of water in the heat exchanger shell.

The advantage of this is that the temperature difference between the refrigerant and the water leaving the system can be a lot smaller. “The difference between the two can be as low as 2 deg C as opposed to 10-15 deg C on a conventional chiller,” claims Mr Strong.

Because the refrigerant always evaporates at about 0 deg C, there also isn’t any need to use anti-freeze on the chillers, nor a risk of any parts freezing and resulting in a costly repair bill.

The chillers use R134A refrigerant, as opposed to R407c that was used in the previous installation. Cool-Therm says that R134A is currently 15 per cent cheaper.

On site

An important design issue for the chillers was to ensure that all pipework connections were positioned and engineered to match those of the existing installation and enable rapid and effective replacement.

To achieve this, one Turbomiser chiller was designed as a left-handed unit and the other as a right-handed unit.

The plant room on the roof had previously been designed in such a way that the control panels could be contained inside to protect maintenance staff working on the chillers. This was replicated for the Turbomiser installation.

Installation was a straightforward process. The original chillers had to be drained of glycol - around 20,000 litres of the antifreeze. The new units could then be slotted into the old connections.

One complication that installer Prima4 had to overcome was lifting the chillers onto the roof. Skandia’s nine-storey building sits in the city centre, so the contractor had to use a crane to lift and swap the new chillers with the existing ones. “Given the location and scale of the task, it required a lot of detailed planning teamwork,” says Prima4 project manager Ralph Birch.

The coastal location of the project also meant that extra work had to be done to protect the life expectancy of the chillers. At the factory, a black epoxy coating was applied to the aluminium condenser coils, protecting them against corrosion from the saline air coming from the sea.

Side panels were also installed, preventing the ubiquitous seagulls from opting to use the chillers as an expensive nesting site. The chillers have also been painted to enable them to blend in with the architecture of the building.

Subsequent savings

With the new chillers installed, Skandia expects to save around 70 tonnes of carbon and £15-20,000 in energy costs per year.

Cool-Therm also claims maintenance costs should be lower, as the system doesn’t need to be drained of glycol and has a lower starting current, resulting in less wear on electrical switch gear.