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Avoid server overheating with ASHRAE data center guidelines

Finding the right server operating temperature can be tricky. ASHRAE standards provide guidance for all server classes and what factors can play into temperature readings.

With rack density continuing to increase in data centers, admins must constantly keep an eye on operating temperatures to ensure their servers can run efficiently without any possibility of overheating.

Instead of guessing on possible temperatures, admins can use ASHRAE data center guidelines to set temperature standards across the data center and incorporate best practices for infrastructure that's cool and produces a low power usage effectiveness (PUE) metric.

What is the best temperature for server operation?

Originally published in 2006, ASHRAE's Thermal Guidelines for Data Processing Environments gives admins a look at ideal operating temperatures. These temperatures ensure that infrastructure can run smoothly, avoid overheating and reduce humidity.

The most recent publication in 2015 set the standard from a low of 59 degrees Fahrenheit to a high of 80.6 degrees Fahrenheit. To address any potential warranty concerns, the technical committee confirmed this operating range with manufacturers.

ASHRAE does not recommend admins simply turn up the thermostat to a higher temperature and establish a new operating temperature. Instead, admins should monitor inlet server temperatures and use that data to inform any temperature increases. Without accounting for inlet temperatures, server hardware could go beyond 80.6 degrees Fahrenheit and cause overheating.

What factors can affect server temperature?

As part of temperature settings, admins must also consider relative humidity. Being aware of humidity levels can also help reach a better PUE rating and reduces water use in the data center.

Older ASHRAE data center guidelines recommended a relative humidity level of 40%-50% to reduce static discharge. Though research proves that there is not as strong a correlation as originally thought. In 2014, ASHRAE changed these guidelines to between 8%-15% relative humidity.

It is also noted that the best way to control humidity levels is to monitor dew point and static conditions. These updated recommendations from ASHRAE take these factors into consideration and point out that dew point temperature is the best way to monitor and control data center moisture.

How hot can admins run their servers?

How to keep server hardware cool and decide on the right temperature is another challenge for admins. This especially depends on the type of hardware an organization runs, as factors such as server processor, heat sink design and available cooling systems will affect any decision.

ASHRAE data center guidelines have recommendations for four main equipment classes: A1, A2, A3 and A4. Most server designs are suited for A1 or A2 temperature ranges, and admins can support A3 and A4 temperatures with specific systems and monitoring.

The dry-bulb temperature ranges for each class are:

  • A1. 59 to 89.6 degrees Fahrenheit with a maximum dew point of 62.6 degrees Fahrenheit.
  • A2. 50 to 95 degrees Fahrenheit with a maximum dew point of 69.8 degrees Fahrenheit.
  • A3. 41 to 104 degrees Fahrenheit with a maximum dew point of 75.2 degrees Fahrenheit.
  • A4. 41 to 113 degrees Fahrenheit with maximum dew point of 75.2 degrees Fahrenheit.

These temperatures are the ranges that the hardware can run at but are not necessarily recommended for long-term operations; ASHRAE has modified guidelines for when the product is powered off.

What ASHRAE data center guidelines can admins use to guide efficiency initiatives?

Part of ASHRAE's goals are to help organizations improve on data center efficiency -- and Standard 90.1 addendum "bv" does just that. This addendum, published in 2019, aims to close the gap between Standards 90.1 and 90.4, help organizations design more energy-efficient infrastructure and make compliance easier for admins.

In addition to renumbering parts of 90.4 to mirror 90.1 language, ASHRAE also updated the standard to:

  • base mechanical efficiency requirements on yearly energy calculations; and
  • address changes in uninterruptable power supply technology for improved mechanical load and electrical calculations for a more accurate electrical loss component.

With these updates to such efficiency standards, organizations not only have a more straightforward idea of how to stay ASHRAE-compliant, but can use the available data center technology to gain a more effective picture of power usage and energy efficiency across all infrastructure.

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