ASHRAE Technical Committee (TC) 9.9 recently released a white paper titled, “2011 Thermal Guidelines for Data Processing Environments-Expanded Data Center Classes and Usage Guidelines,” (which can be downloaded free from www.tc99.ashraetcs.org). The key data in this white paper will be included in the third edition of ASHRAE’s Thermal Guidelines for Data Processing Environments. The white paper responds to increasing requests from the industry for ASHRAE to expand its temperature ranges for data centers.
Although cooling system efficiency and PUE benefits are well known, operating data centers at higher temperatures can bring additional IT equipment cost, acoustic, and compute impacts benefits. As a result, ASHRAE focused on providing flexibility and options by increasing the number of data center classes to four. These are designated A1 to A4, with Class A4 having the broadest temperature range (41° to 113°F). The biggest tradeoff is IT equipment reliability vs. the ability for the facility to operate full time in economizer mode (compressor-less/chiller-less).
Other highlights of the newly published TC 9.9 white paper includes the effect of expanded envelopes on IT equipment and vendor-neutral IT equipment reliability at varying temperatures that has never been published before.
Obtaining the endorsement of the major IT equipment manufacturers was critical to TC 9.9’s success in creating universally accepted thermal guidelines. Further, these vendor endorsements include legacy equipment. Since most data centers are a multi-vendor and multi-generation environment from an IT equipment perspective, it is important to publish environmental requirements that include all equipment in the data center. To develop these guidelines, the voting members of TC 9.9 (a cross section of industry representatives such as owners, consultants, and manufacturers) reviewed and approved a set of recommendations provided by a subcommittee of commercial IT equipment manufacturers.
The first two editions of the ASHRAE book Thermal Guidelines for Data Processing Environments established two data center environmental classes (Class 1 and 2). The first edition started with a recommended range for both data center classes of 68° to 77°F. The second edition expanded the recommended range (64.4° to 80.6°F). Both of these ranges applied to both new and legacy equipment and were intended to avoid adverse impacts on server cost, acoustics, form factor, performance, and other aspects.
The thermal guidelines book defined the measurement and monitoring points for auditing facility performance/health. Temperature ranges are measured at the inlet to the IT equipment (see figure 1). Having consistent measurement and monitoring points facilitates the ability to provide succinct guidelines.
The white paper creates two additional data center classes for a total of four data center classes and six classes in total. The nomenclature has been changed to avoid confusion. The data center-specific classes are labeled A1 to A4, and the non-data center classes (previously called Class 3 and 4) are now called B and C. Classes A1 and A2 are the same as the original Class 1 and Class 2. The two new data center classes are called A3 and A4.
(For consistency, all tables referenced in this article utilize the same names as those in the white paper. Further, the tables have been modified for clarity within the context of this article and original footnotes have not been included. The reader is encouraged to read the entire white paper to obtain a full understanding.)