Industry Standard on Chillers Puts More Emphasis on Part-Load Efficiency

One of the most challenging aspects of managing a data center – and there are many – is staying updated and informed on government regulations and industry standards that impact data center operations.

While there are numerous regulations and standards of which to keep track, one of the most important regulations that is creating major changes on the thermal management side is ASHRAE 90.1. The 2010 and 2013 versions of these standards, which provide minimum requirements for energy efficient designs for buildings, are having a significant impact on the design of all mechanical equipment for data centers, including chillers. In fact, the 2013 revision is putting more emphasis on part-load efficiency across the chiller market, which is a positive development.

Before ASHRAE 90.1-2010 was published, data centers were not required to meet any minimum efficiency. The 2010 version introduced minimum computer room air conditioner (CRAC) unit efficiencies. This version also stipulated incorporating economizers into the thermal management system design in new commercial buildings, depending on design, weather conditions and system cooling capacity.

With the publication of ASHRAE 90.1-2013, an alternative method for data center efficiency was added to show compliance. That method, based on performance requirements rather than prescriptive ones, entails minimum Power Usage Effectiveness (PUE) values for each of the ASHRAE climate zones and results in a calculated number based on the data center design. This was done because the prescriptive measures in the standard have been viewed by some as inflexible given how often IT technology changes and the fact that emerging thermal management strategies require changes in data center design.

The 2013 revision of the standard also required EER ratings for air-cooled chillers that represent more than a 5 percent increase in required efficiency over the 2010 edition. More critically, this revision included almost a 10 percent increase in the required part-load efficiencies of chiller systems, which is a more accurate measure of their real-world performance.

This 10 percent increase is helping to cause a shift across the chiller market to place more significance on part-load efficiency. This is a good thing. Because of the critical nature of data center operations, levels of “redundancy” or excess capacity are designed into thermal management systems. This leads to the majority of data centers running at much less than 100 percent of their chiller capacity. This fact, combined with the 24/7 operation of data center facilities, means that part-load efficiency is the most vital measure of a chiller’s efficiency for a data center application. Engineers and contractors understand this fact, and design facilities based on these part-load conditions.

So far, 18 states have adopted ASHRAE 90.1-2010, while two states, Maryland and Vermont, have adopted the 2013 revision. With the large amount of data center activity in the Washington D.C. area, the Maryland adoption of the code is significant.

No one can really predict which states will adopt new versions of 90.1, or when. This is why at Emerson Network Power we make sure to keep our product offerings in line with all coming standards to ensure that are ready when additional states do adopt the new requirements. In fact, all our mission critical air-cooled chillers exceed ASHRAE efficiency requirements for both full and part-load conditions.

As standards continue to change and states continue to adopt the revisions, it is important that all stake-holders – data center managers, contracts and engineers stay current and educated on the requirements for their systems to ensure they meet all applicable standards.

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Steven Bartoszewicz