Committee of the US-based organization that sets a well-accepted range of allowable temperature and humidity conditions in data centers will raise the upper temperature limit for the second time since the guidelines were first published.

American Society of Heating, Refrigerating and Air-Conditioning Engineers announced that the upcoming third edition of its "Thermal Guidelines for Data Processing Environments" publication will specify a wider envelope for IT-equipment-friendly temperature and humidity inside data centers than the current edition does.

First edition of the guidelines, published in 2004, set the upper temperature limit at 77F (25C). Four years later, the second edition raised the limit to 81F (27C).

Don Beaty, Publications Subcommittee chair for ASHRAE's Technical Committee 9.9, said the first edition was successful in unifying the industry on the subject of allowable environmental envelope for IT equipment. The second edition, he added, enabled the use of economizers in a wider range of locations.

Scope of the committee (TC 9.9) covers all data processing and communication facilities ÔÇô from IT closets to fully-fledged data centers.

The third edition, Beaty said, would be "equally groundbreaking", as it will enable cooling without the use of any compressors, or 100% economization, in many circumstances.

"Different locations, applications and business philosophies make it ineffective to force all equipment to be capable of the same high temperature tolerance (in some cases higher thresholds would negatively impact the return on investment)," Beaty said.

"To address this, the third edition creates multiple server classes and therefore provides freedom of choice. This is particularly important since the thermal guidelines are used throughout the world."