In an average data centre, cooling constitutes for as much as 50% of the total power consumed and can account for as much as 40-60 percent of operational cost. It is therefore unsurprising that data centres are constantly seeking innovative ways to reduce their energy consumption and subsequently save on running cost. To achieve energy savings and performance increases, a major telecommunications provider required a trial retro t installation of their existing computer room air conditioning (CRAC) units throughout a building to identify what savings could be achieved.