Data centers’ intricate design: Codes and standards
Data centers are important structures that hold vital information for businesses, schools, public agencies, and private individuals. A variety of codes and standards guide engineers in designing these data centers.
Tim Chadwick, PE, LEED AP, President, AlfaTech Consulting Engineers, San Jose, Calif.
Robert C. Eichelman, PE, LEED AP, ATD, DCEP, Technical Director, EYP Architecture & Engineering, Albany, N.Y.
Barton Hogge, PE, ATD, LEED AP, Principal, Affiliated Engineers Inc., Chapel Hill, N.C.
Bill Kosik, PE, CEM, LEED AP, BEMP, Building Energy Technologist, Chicago
Keith Lane, PE, RCDD, NTS, RTPM, LC, LEED AP BD+C, President/Chief Engineer, Lane Coburn & Associates LLC, Seattle
Robert Sty, PE, SCPM, LEDC AP, Principal, Technologies Studio Leader, SmithGroupJJR, Phoenix
Debra Vieira, PE, ATD, LEEP AP, Senior Electrical Engineer, CH2M, Portland, Ore.
CSE: Please explain some of the codes, standards, and guidelines you use. Which codes/standards should engineers be most aware of in their design?
Sty: Designers should be knowledgeable of the current local codes as they are legal minimum standards for facility design; but they are just that, the minimum level of design and construction. Some facilities (depends on the owner) justify meeting the requirements of physical security set by the Interagency Security Committee. ASHRAE, the U.S. Green Building Council (USGBC), and The Green Grid all have standards relating to energy efficiency that designers should be familiar with and implement. The Uptime Institute has set the bar for reliability standards in their Tier certification process.
I believe that anyone involved in the data center industry should understand the true nature and requirements of the Tier level descriptions, as those are probably the most often misused in describing the robustness of a facility. Many times, I hear people use the term "Tier 2 plus," which is incorrect as there is no such thing. We should also be cautious in our descriptions when we state a facility is a certain Tier level if it hasn't actually been certified by the Uptime Institute.
Vieira: As an electrical engineer, the codes that I most frequently reference for U.S.-based projects are the NFPA 70: National Electrical Code, NFPA 70E: Standard for Electrical Safety in the Workplace, NFPA 101: Life Safety Code, and NFPA 110: Standard for Emergency and Standby Power Systems. Compliance with these codes creates an electrical system that is safe to operate and maintain. Adherence to data center industry guidelines—such as Uptime Institute Tier classification system or the level-based topology found in ANSI/TIA-942, Telecommunications Infrastructure Standard for Data Centers—varies based on project requirements. Rarely does a data center design meet the strict definitions of a tier/level.
Eichelman: There are several standards that are written specifically for data centers. These include NFPA 75: Standard for the Fire Protection of Information Technology Equipment; NFPA 70, Articles 645 and 708; Uptime Institute Data Center Site Infrastructure Tier Standard Topology; TIA-942; USGBC LEED v4; and ASHRAE Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings. NFPA and ASHRAE standards are typically, but not always, referenced directly by the applicable building code for a project, but are considered best practices nonetheless. Uptime Institute, TIA, and USGBC standards offer best practices, depending on the nature, reliability requirements, and energy efficiency goals of the facility. Executive Order EO 13693, issued by the White House, includes specific requirements related to energy consumption for all existing and new federal data centers.
Hogge: Beyond the obvious code-mandated requirements, engineers and owners should discuss best-practice standards when creating the owner project requirements. The Uptime Institute, TIA-942, ASHRAE TC9.9, and The Green Grid are commonly cited standards. It is important that the team agree on strict interpretation of standards, or what we call "guiding principles." Oftentimes, the budget, space constraints, and values of the end user will already direct the design to follow the spirit of a standard within the practical limits. Clear understanding among all stakeholders is extremely important as the project moves through design, commissioning, and operation.
Chadwick: ASHRAE TC9.9 is continually updating engineers on the capabilities of server and storage equipment. The first question that needs to be asked for data center cooling is always what will the inlet temperature/humidity be for the design? This impacts the entire cooling strategy. ASHRAE Standard 90.4P, Energy Standard for Data Centers and Telecommunications Buildings, will be the minimum efficiency standard for data centers when it is released this summer (release pending final reviews). This standard will establish the minimum performance. As with the original issuance of ASHRAE 90.1, Standard 90.4 is aimed to set the bar at an achievable, but not overly burdensome level. Over time, these standards will be incrementally tightened to drive improvements in efficiency. This is, of course, a minimum standard; there are many examples of data center designs that greatly exceed these standards.
CSE: How have International Building Code, NFPA, ASHRAE, and other codes affected your work on such projects? What are some positive/negative aspects of these guides?
Hogge: The significant impact of ICC2015/ASHRAE 90.1-2013 economization requirements will be a more prescriptive approach to design, and it will likely require the use of MEP infrastructure components that may not make sense for a given facility or geographic location. Two different resolutions are being proposed to revise this, one being a new proposed standard: ASHRAE 90.4P.
Kosik: What I have found is that the facilities and IT industries have typically developed design approaches to solve specific issues. From these solutions, standards and guidelines are published; this process combines the experience gained from the "real-world" applications and the knowledge of how standards and guidelines are established to ensure applicability to a wide range of project types. Also, in many instances, the industry organization responsible for publishing the standards and guidelines will invite a team of industry experts to form a committee to assist in writing the technical documentation.
Sty: Standards and guidelines, such as those set forth by ASHRAE TC9.9 on thermal guidelines for data-processing environments, helped drive a shift in energy efficiency. As the window for entering-air temperatures expanded, so did the use of aisle containment and economizer strategies. Free cooling operation is very energy-efficient, but can lead to other problems if not designed correctly. The system must include proper filtration of any particulates entering from the outside. Control strategies must ensure that the rate of change of temperature/relative humidity at the data floor is within acceptable ranges. This can potentially be a complex process if the system is to respond to take full advantage of the outside environmental conditions. The PUE metric developed by The Green Grid has given the industry a target to describe the efficiency of a data center. The definition and calculation of the PUE metric have evolved over the years to give a more realistic view of a data center's operating efficiency. No longer is it acceptable to take a single reading on the coldest day of the year and use that as the reported efficiency of the facility. Reporting based on continuous measurement of the efficiency of the data center gives a far more realistic profile of the facility.
Chadwick: The current codes were not necessarily written with the unique needs and requirements of data centers in mind. That is why there is such a strong need for the new ASHRAE 90.4 standard. Some prescriptive requirements in the current codes are in stark contrast with some of the specific needs of data centers.