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If you’ve ever done anything even remotely related to HVAC, you’ve probably encountered ASHRAE at some point. The American Society of Heating, Refrigerating and Air-Conditioning Engineers is a widely influential organization that sets all sorts of industry guidelines. Though you don’t technically have to follow ASHRAE standards, doing so can make your systems a lot more effective and energy efficient. This guide will cover all the basics so that you can make sure your data centers get appropriate cooling.

What Are the ASHRAE Equipment Classes?

One of the key parts of ASHRAE Data Center Cooling Standards is the equipment classes. All basic IT equipment is divided into various classes based on what the equipment is and how it should run. If you’ve encountered ASHRAE standards before, you may already know a little about these classes. However, they have been updated recently, so it’s a good idea to go over them again, just in case. These classes are defined in ASHRAE TC 9.9.

  • A1: This class contains enterprise servers and other storage products. A1 equipment requires the strictest level of environmental control.
  • A2: A2 equipment is general volume servers, storage products, personal computers, and workstations.
  • A3: A3 is fairly similar to the A2 class, containing a lot of personal computers, private workstations, and volume servers. However, A3 equipment can withstand a far broader range of temperatures.
  • A4: This has the broadest range of allowable temperatures. It applies to certain types of IT equipment like personal computers, storage products, workstations, and volume servers.[1]

Recommended Temperature and Humidity for ASHRAE Classes

The primary purpose of ASHRAE classes is to figure out what operating conditions equipment needs. Once you use ASHRAE resources to find the right class for a specific product, you just need to ensure the server room climate is meeting these needs.

First of all, the server room’s overall temperature needs to meet ASHRAE standards for its class. ASHRAE standards always recommend that equipment be kept between 18 to 27 degrees Celsius when possible. However, each class has a much broader allowable operating range.[1] These guidelines are:

  • A1: Operating temperatures should be between 15°C (59°F) to 32°C (89.6°F).
  • A2: Operating temperatures should be between 10°C (50°F) to 35°C (95°F).
  • A3: Operating temperatures should be between 5°C (41°F) to 40°C (104°F).
  • A4: Operating temperatures should be between 5°C (41°F) to 45°C (113°F).[1]

You also need to pay close attention to humidity. Humidity is a little more complex to measure than temperature. Technicians will need to look at both dew point, which is the temperature when the air is saturated, and relative humidity, which is the percent the air is saturated at any given temperature.[2] Humidity standards for ASHRAE classes are as follows:

  • A1: Maximum dew point should be no more than 17°C (62.6°F). Relative humidity should be between 20% and 80%.
  • A2: Maximum dew point should be no more than 21°C (69.8°F). Relative humidity should be between 20% and 80%.
  • A3: Maximum dew point should be no more than 24°C (75.2°F). Relative humidity should be between 8% and 85%.
  • A4: Maximum dew point should be no more than 24°C (75.2°F). Relative humidity should be between 8% and 90%.[1]

Tips for Designing Rooms to Meet ASHRAE Data Center Cooling Standards

As you can see, ASHRAE guidelines are fairly broad. Just about any quality precision cooling system can easily achieve ASHRAE standards in a data center. However, a good design should do more than just consistently hit a temperature range. Planning the right design carefully can help reduce energy usage and make it easier to work in the data center. There are all sorts of factors you will need to consider.

Since most companies also want to save energy, it can be tempting to design a cooling system that operates toward the maximum allowable ASHRAE guidelines. However, higher operating temperatures can end up shortening equipment’s life span and causing inefficiently operated technology to use more power.[3] Carefully analyzing these costs can help companies find the right temperature range for their system.

Once you have a desired temperature set, it’s time to start looking at some cooling products. CRAC and CRAH units are always a reliable and effective option for data centers of all sizes. Another increasingly popular approach is a fluid cooler system that uses fluid to disperse heat away from high temperature systems. Many companies in cooler climates are also switching to environmental economizer cooling systems that pull in cold air from the outdoors.[3]

Much of data center design focuses on arranging HVAC products in a way that provides extra efficiency. Setting up hot and cold aisles can be a simple and beneficial technique. This involves placing server aisles back-to-back so the hot air that vents out the back flows in a single stream to the exit vent. You may also want to consider a raised floor configuration, where cold air enters through a floor cooling unit. This employs heat’s tendency to rise, so cooling air is pulled throughout the room.[4] By carefully designing airflow and product placement, you can achieve ASHRAE standards while improving efficiency.

Data Aire Is Here to Help

If you have any questions about following ASHRAE Data Center Cooling Standards, turn to the experts! At Data Aire, all of our technicians are fully trained in the latest ASHRAE standards. We are happy to explain the standards to you in depth and help you meet these standards for your data room. Our precision cooling solutions provide both advanced environmental control and efficient energy usage.




[1] https://www.chiltrix.com/documents/HP-ASHRAE.pdf
[2] https://www.chicagotribune.com/weather/ct-wea-0907-asktom-20160906-column.html
[3] https://www.ibm.com/downloads/cas/1Q94RPGE
[4] https://www.simscale.com/blog/2018/02/data-center-cooling-ashrae-90-4/