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What are the Best Humidity Levels for Data Centres?

21 March, 2016

data centre humidityIs everything we thought we knew about the most effective humidity levels for data centres about to change? New research certainly seems to suggest so. After maintaining relative humidity levels of 45-50% for decades in datacentres, the assumption that we need to keep humidity high to avoid problems with static discharge has now been dispelled.

A research study commissioned by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has found that the danger to IT equipment from static discharge is insignificant at as low as 15% relative humidity. The study also found that the humidity can be dropped as low as 8% relative humidity with only minor precautions necessary to prevent static discharge problems.

The tests carried out by the ASHRAE team involves a multitude of different types of floor tiles and clothing, in various combinations. The research found that between 8% and 25% humidity, the difference in static electricity is insignificant, no matter which floor tiles and clothing combinations were used.

So how will this revelation affect datacentres? First of all, it allows datacentres to save enormous amounts of energy. With desired relative humidity rates as low as 8%, datacentres don’t need to vapourise huge amounts of water to create this environment. Datacentres that are situated in colder climates could even get by without any form of humidification for most of the year. Don Beaty, ASHRAE fellow, confirmed that the point of expanding the humidity envelope parameters was to enable more free-cooling hours in colder climates, without needing to bring in artificial humidification.

There are also implications for the cooling practices of many data centres. Humidity and temperature are intrinsically linked, and with lower recommended humidity rates, temperatures can be increased too. This gives data centres increased opportunity to use the external climate as part of their cooling endeavours – evaporative cooling, for example. “The hotter you can operate inside the temperature, the more you can use the climate that’s outside,” said Mr Beaty.

Of course, there are datacentres out there that may feel uncomfortable about dropping their humidity rates, which might previously have measured 50%, down to 8% overnight. Protecting their IT equipment and maintaining a reliable operation is the biggest priority for these firms, and some might be reluctant to implement such a huge change in recommended best practice. For businesses unwilling to immediately drop down to 8% humidity, the recommendation is to start be controlling temperature and moisture levels slightly below the ASHRAE limits, to ‘test the water’, as it were. 

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