ATLANTA – ASHRAE continues to widen the temperature and humidity ranges for servers through a soon-to-be-published third edition of the datacom book, “Thermal Guidelines for Data Processing Environments.”

The first edition was published in 2004 and was groundbreaking in that it created the first global, vendor neutral environmental specification for data centers, according to Don Beaty, chair of the Publications Subcommittee of ASHRAE’s Technical Committee (TC) 9.9, Mission Critical Facilities, Technology Spaces and Electronic Equipment.  Prior to its publication, data center temperature requirements were set individually by each equipment manufacturer.  This typically resulted in using the most stringent temperature plus a safety factor being used across the entirety of the data center. 

The approach used by TC 9.9 for the first edition through to the present was to assemble a team of thermal engineers from the major commercial IT manufacturers to develop requirements.  The first edition created a recommended temperature upper limit of 77 F (25 C), promoting the use of higher temperatures and endorsed by all of the IT manufacturers.

The second edition (2008) took considerable deliberation amongst the manufacturers and raised the recommended upper limit to 81 F (27 C).  Both the first and second editions were groundbreaking (the first edition in unifying the industry and the second edition in enabling the potential to use economizers in many locations and applications), according to Beaty.

The third edition will be equally groundbreaking in that it will enable compressorless cooling (all cooling through economizers) in many applications.  Accomplishing this has been a challenge since major tradeoffs (equipment size, equipment cost and operating cost) surface above a certain temperature threshold.  This challenge is complicated because the threshold is not the same for all the manufacturers.

“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.”

Editors Note: The following information provides additional background information on TC 9.9 and the proposed environmental classes.

ASHRAE TC 9.9 was started in 2002 to be recognized by all areas of the datacom industry as the unbiased engineering leader in HVAC and an effective provider of technical datacom information, according to Beaty. Its scope covers all datacom (data processing and communication) facilities including rooms or closets used for communication, computers or electronic equipment.

The first initiative of TC 9.9 was to publish the book, “Thermal Guideline for Data Processing Environments.”  Prior to TC 9.9, commercial IT manufacturers published their own, independent temperature specifications. Typical data center temperatures were 20 or 21 C and a common notion of cold is better. 

However, most data centers are multi-vendor, resulting in the temperature defaulting to the most stringent requirement plus a safety factor. 

TC 9.9 obtained informal consensus from the major commercial IT manufacturers for both “recommended” and “allowable” temperature/humidity ranges and for four environmental classes.

Another critical accomplishment was to establish IT equipment air inlets as the common measurement point for temperature and humidity compliance; requirements in any other location within the data center were optional. 

The global interest in expanding the temperature and humidity ranges continues to increase.  In 2008, TC 9.9 revised the requirements for Class 1 and 2 to be less stringent.  The following are the current allowable and recommended maximum dry bulb temperatures:

• Class 1 – 32 C Allowable;  27 C Recommended 

• Class 2 – 35 C Allowable;  27 C Recommended 

• Class 3 – 35 C Allowable;  N/A   Recommended (no environmental control)

• Class 4 – 40 C Allowable;  N/A   Recommended (no environmental control)

Increasing the temperature and humidity ranges increases the opportunity to use compressorless cooling solutions.  Typically the equipment selected for data centers are either Class 1 or 2.  Class 3 is for applications such as personal computers and Class 4 is for applications such as “point of sale” IT equipment used indoors or outdoors. 

These environmental specifications/classes are really the domain and expertise of IT OEMs.  TC 9.9’s IT Subcommittee is exclusively compromised of engineers from commercial IT manufacturers; the subcommittee is strictly technical.  

The commercial IT manufacturers’ proprietary design, field and failure data is shared (to some extent) within this IT Subcommittee enabling greater levels of disclosure and ultimate expansion of the environmental specifications.  

“Prior to TC 9.9, there were no organizations or forums to remove the barrier of sharing proprietary information amongst competitors,” Beaty said. “This is critical since having some manufacturers conform while others do not, returns to the trap of a multi-vendor data center where the most stringent requirement plus safety factor or most likely preside.  The IT manufacturers negotiated amongst themselves in private resulting in achieving some critical sharing of proprietary information.”

From an end user perspective, it is also important that they be provided with options for their multi-vendor facilities such as:

• Option 1 – use IT equipment optimized for a combination of attributes including energy efficiency but the dominant attribute being capital cost.

• Option 2 - use IT equipment optimized for a combination of attributes including some level of reliability but the dominant attribute being energy and compressorless cooling 

The industry needs both types of equipment but also needs to avoid Option 2 increasing the cost of Option 1 by increasing manufacturing costs through mandatory requirements not desired or used by all end users.  Expanding the temperature and humidity ranges can increase the physical size of the IT equipment (e.g. more heat transfer area required), increase IT equipment air flow, etc.  This can impact embedded energy cost and IT equipment cost.  

ASHRAE is an international technical society that fulfills its mission of advancing heating, ventilation, air conditioning and refrigeration to serve humanity and promote a sustainable world through research, standards writing, publishing and continuing education.