Bypass Airflow: How it Affects Your Data Center’s Bottom Line7 min read

by | Sep 25, 2013 | Blog

Did you know that 48% of conditioned air in the average data center escapes through unsealed cable openings and misplaced perforated tiles? In fact, the average data center could save as much as $32,000 per year in electric costs by eliminating bypass airflow.

When your data center has common openings like these, it obviously requires you to run more fans to provide vital conditioned air to your heat load. This state of cooling inefficiency is a prime example of bypass airflow, which is any conditioned air supplied by a cooling unit that does not pass through (bypasses) IT equipment before returning to a cooling unit.

Are you also aware that the holes in a raised floor and excessive volumes of cold air in a cold aisle are two principal sources of bypass airflow? It’s common knowledge that installing grommets to seal cable openings in a raised floor and blanking panels in cabinets are best practices for eliminating hot spots, as well as prerequisites for efficiently operating any computer room cooling configuration. Ironically, it’s also common to find that these fundamental steps were overlooked or left unfinished before sites began implementing advanced airflow management (AFM) solutions, such as hot or cold aisle containment.

Improving your AFM is the right solution for reducing bypass airflow, as well as for reducing your operating costs. However, despite the multitude of AFM and containment solutions available today, an average data center still has nearly four times more cooling capacity than IT load. As a result, bypass airflow volumes remain high and the full potential benefits of these best practices remain unrecognized.
Similarly, there’s a widespread misconception that managing raised floor openings or installing full containment solutions will totally eliminate bypass airflow. While these actions help to solve intake air temperature problems, and may reduce IT cooling fan operating costs, bypass airflow volume in the room actually remains unchanged. Detecting and then correcting this room-level issue requires an understanding of the broader definition and sources of bypass airflow. Data center managers will then be able to identify significant opportunities to increase their cooling capacity and reduce their operating costs.

Following are four basic steps that you can take to reduce bypass airflow in your data center:

1. Measure your computer room’s existing CCF to get a context for opportunities to improve.

2. Improve AFM by making the necessary changes at each of the following three levels in the proper sequence—Raised floor, Rack, and then Row.

3. Change the cooling infrastructure control set points and number of running cooling units (if possible).

4. Repeat this process to ensure your cooling infrastructure is optimized.

Lars Strong

Lars Strong

Senior Engineer


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