Standards Finally Emerge for Data Center Temperatures

A set of guidelines from an industry-leading organization finally put numbers and measurement techniques to the question—how hot is too hot?

Keeping your data center at the right temperature sounds mundane, but it's critical for the life of your equipment. Both temperatures and rate of temperature change are important statistics for maintaining reliability, remaining within the electronic equipment warranty constraints, energy usage, and troubleshooting. Trouble is, few published guidelines or standards for datacom (data processing and communications) facilities exist that deal with the optimum way to capture this data. Datacom managers have had to be content with a combination of the numbers stated in equipment manuals, personal experience, and legacy standards from the early mainframe days. Since most datacom facilities are mission critical, vagueness for such a critical metric is very unsettling.

Fortunately there is now a guideline that addresses operating temperatures, temperature change rates, and humidity for a variety of facilities. The publication, “Thermal Guidelines for Data Processing Environments,” is published by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

While the building cooling industry is familiar with ASHRAE, the IT community is relatively unfamiliar and often unsure where to turn for cooling guidance.. ASHRAE is a non-profit organization that has been serving the building cooling industry for over 100 years, has over 50,000 members, and is working to be the same reliable source of information for the IT industry.

In the past, the facilities and IT industries have operated in an independent manner. However, the continuing trend towards more compact technology equipment creating high-density heat loads and the inability to effectively cool the IT environment is presenting a considerable challenge, which in turn is driving the need for a more holistic and collaborative approach between the two industries.

In 2001, that combined approach began as ASHRAE Technical Committee “TC 9.9—Mission Critical Facilities, Technology Spaces, and Electronic Equipment.” Membership included leaders from both industries. This committee has already produced numerous papers and symposia, and is responsible for Thermal Guidelines.

The publication provides critical information on environmental conditions and its measurement from an impartial or unbiased source that can easily be referenced for operating policies and service-level agreements. The guidelines establishe four environmental classes and the associated environmental conditions for each class. For example, a typical data center would be an Environmental Class 1, and ASHRAE suggests a variety of temperature guidelines, including temperatures, humidity levels, and maximum rate of temperature change per hour.

In many cases, these environmental conditions are less stringent than those that are set independently based on experience or legacy policies. The publication establishes recommended as well as allowable values, warning that prolonged exposure of operating equipment to conditions outside its recommended range can result in decreased equipment reliability and longevity. Even more important, it warns that exposure of operating equipment to conditions "outside its allowable operating environment risks catastrophic equipment failure."

Many of the major IT equipment manufacturers participated in preparing this information, keeping it independent of one specific product or manufacturer. Among the participants: IBM, HP, Sun, Intel, Cisco, Cray, Hitachi, EMC, Dell, Lucent, NCR, Motorola, Unisys, and Fujitsu.

Specific "allowable" and "recommended" environmental condition standards is a great help, of course, but complicating the standards is the issue of where these temperatures are measured and whether they are averages or maximum thresholds. Typically, prior to the guidelines, the definition and location of temperature measurements varied depending on personal preferences, experiences, and legacies, or were slanted towards proving a particular viewpoint.

Traditional measurement points have varied in height: near the floor, waist high, 4 feet 9 inches above the floor, and eye height to the top of the rack, among others. Temperature measurements for other types of buildings are often associated with human occupancy, which may be why there is such variation in where to measure the temperature in a datacom facility where the “occupancy” is electronic equipment.

The guidelines clearly define the measurement points for temperatures: the critical temperatures are the cold aisle in a hot/cold aisle configuration and the equipment air inlets. There are simple diagrams and guidelines provided to assist in locating the points. Measurement points, values, and guidelines are intended for:

  • Facility health and audit tests
  • Equipment installation verification tests
  • Equipment troubleshooting tests

Temperatures are a critical element for datacom facilities for effective design and operation. The benefit of ASHRAE's published guidelines is that it provides these environmental conditions (and how to measure them) from an impartial source that can be easily referenced.

More information can be found at

About the Author

Don Beaty, PE, is the founder of DLB Associates Consulting Engineers PC, a mechanical and electrical engineering firm licensed in over 40 states, and is founding chair of ASHRAE Technical Committee (TC9.9) for Mission Critical Facilities, Technology Spaces, and Electronic Equipment. He can be reached at