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Use ASHRAE guidelines to get server temperature right

The main factors that affect server efficiency are inlet air temperature, humidity and contaminants. Follow these ASHRAE guidelines to set up the right facility for your hardware and save energy.

Your operating environment is as important to system availability as reliable power and software. If you follow the latest industry recommendations, you can preserve your operation and also save energy.

There are three major factors that affect your data center operating environment and server temperature: inlet air temperature, humidity, and particulate and gaseous contaminants.

The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) set the inlet air temperature standard in 2006 with the publication of Thermal Guidelines for Data Processing Environments, as part of the Datacom series from Technical Committee 9.9.

The book sets both the recommended and allowable temperature and humidity ranges for data center hardware. ASHRAE published the most recent version -- the fourth edition -- in 2015.

The committee's specified ranges significantly increase the temperature at which you can safely operate computing hardware, taking a giant leap above the 55 degrees Fahrenheit that had long been the conventional wisdom for data center facilities.

ASHRAE's recommended temperature range now goes from a low of 59 degrees Fahrenheit to a high of 80.6 degrees Fahrenheit, making the minimum warmer than the traditional norm in computer rooms. Major computing system manufacturers agreed to these numbers to eliminate any warranty concerns.

Thermal Guidelines also established a dew point temperature, or absolute humidity, as the most reliable method to monitor and control data center moisture content. Since the guide's initial publication, the committee has added data on increased temperature versus failure rates and higher limits for special classes of equipment.

Addressing humidity and static

In 2016, ASHRAE research demonstrated that, even with relative humidity as low as 8%, generated static charge levels are not sufficient enough to harm rackmounted computing hardware. Of course, at any humidity level, grounded wrist straps must be worn when working inside hardware.

This is another radical change, but because humidity is best controlled on dew point and static conditions are associated with relative humidity, the recommendations were modified to correlate the two. Now, with almost no exceptions, the data center's floor materials, technician clothing and footwear do not create static conditions at these low humidity levels.

These changes mean you can safely operate equipment in a warmer and less humid environment than traditionally thought, thereby saving an enormous amount of energy and electrical cost.

As a precaution, do not simply increase your air conditioners to 80 degrees Fahrenheit and shut off humidifiers; ASHRAE's recommendations are for server inlet temperature. Unless you have well-controlled air distribution, doing this could cause inlet temperatures to go considerably higher than 80 degrees Fahrenheit, particularly at the top of racks if server exhaust air spills over the tops or around the ends of cabinets.

Instead, increase set points in small increments, and monitor the server inlet temperatures at your cabinets. You can add temperature/humidity probes to most cabinet plug strips or power distribution units to track any changes. Install containment hardware if you recirculate exhaust air.

Keeping on top of contamination

Contamination can negate your energy saving efforts. Particulates, which include dust and dirt, as well as flake-off from fireproofing, unprotected concrete and ceiling panels, can accumulate in server intake fans and filters.

These particulates make fans work harder, which consumes more energy and affects server temperature. Incoming air should be prefiltered, particularly where there's construction, heavy traffic or pollens. You should regularly inspect and change server intake and air conditioner filters.

Gaseous contamination is different. Sulfurs and hydrocarbons combine with moisture above 60% relative humidity to form acids that erode solder joints and connectors. If the outdoor environment is suspect, a lab analysis of the corrosive effects of your air on silver and copper components can identify potential problems. Prefiltering outside air is recommended, but the form of contamination determines the specific filter type you must use.

This was last published in July 2019

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