The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has revised its energy standard for data centers.

The ANSI/ASHRAE Standard 90.4-2019, Energy Standard for Data Centers, sets the minimum energy-efficiency requirements for the design and operation of data centers, with facilities defined as buildings with a conditioned floor area greater than 20W/sq ft and IT equipment loads greater than 10kW.

Standard 90.4 is a performance-based design standard that offers the design components for mechanical load (MLC) and electrical loss (ELC). Calculations of the MLC and ELC are made and then compared to the maximum allowable values, which vary across different climate zones. Compliance with Standard 90.4 is achieved when the calculated values do not exceed the values contained in the standard. An alternative compliance path is provided that allows tradeoffs between the MLC and ELC.

Standard stuff

Data center
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The updates renumber sections and tweaks the wording to align 90.4 more closely with Standard 90.1, the wider Energy Standard for Buildings.

The new revision also no longer includes a power calculation option for mechanical efficiency requirements, which are now based entirely on yearly energy calculations. Included table values are also aligned with the newest ASHRAE Climate Zones.

Most drastically, the revision includes "significant improvements" to how it handles uninterruptible power supply (UPS) technology. Mechanical and electrical infrastructure elements are addressed. Updated UPS segment tables reflect available hardware, and average outputs are also included.

“Standard 90.4 was developed under the guiding principle that data centers are mission-critical facilities that demand careful attention to the potential impact of requirements,” said Richard Zbin, chair of the Standard 90.4 committee.

“The updated standard enables operators and designers to use the latest and most effective equipment and techniques to achieve energy efficiency in data centers, while avoiding potential reliability issues.”

90.4 was first rolled out in 2016, after years of deliberation. An initial draft version included provisions for maximum permissible PUE levels, but all references to PUE were removed from the final version after that proved controversial.