Sealing the Rack: How and Why You Need to Do It
It goes without saying, sealing the open gaps in the rack is a well known best practice when implementing an airflow management strategy. Sealing these gaps within and along the sides of cabinets can lead to many benefits within the data center including cost savings, increased equipment reliability, and efficiency to name a few. However, like any other airflow management initiative, how you implement this step is crucial to effectively achieving these benefits.
Before we get into all of this, one thing to point out is that the goal of all airflow management initiatives is to improve the intake air temperatures to IT equipment. More specifically, to reduce the highest intake air temperatures so that all intake temperatures are as low and even as possible. This, in return, enables changing the control of cooling infrastructure to improve efficiency and increase capacity. In order to achieve these goals, there are many steps along the way that need to be taken in order to optimize airflow and thermal management. One thing to keep in mind is optimization is a process, not an event. Our 4 R’s Methodology provides a protocol to follow in order to achieve this process. Just as a reference, the 4 R’s are: 1. Raised Floor, 2. Rack, 3. Row, and 4. Room.
How you need to do it
After properly managing the open area of the horizontal plane of the raised floor (the 1st R), the next step is properly seal the rack, which includes closing all open space of the vertical plane of IT equipment intakes. There are two primary locations to properly seal the rack:
1. Open U spaces. Obviously sealing open U spaces by installing blanking panels has become a common best practice, however it is surprising how many sites still have not achieved 100% blanking panel use. Also most blanking panels available do not seal effectively. Many leave a 1/16” to 1/8” gap between adjacent panels. Even at just a 1/16” gap between panels in a 42U cabinet filled with blanking panels there will be 45.5 in² area left open (41 spaces x 17.75” between rails x 0.0625” gap = 45.5 in2). This is equivalent to the open area of 1.5 missing blanking panels.
2. Rails to the sides of the cabinets. Also very important is sealing the open space between the rails and the sides of cabinets. In some cabinets this space is sealed by design, however in many it is left open. Often blanking panels have been installed but this space remains open becoming the primary location of both exhaust air circulation to the front of the cabinet or loss of conditioned airflow through the cabinet. In cabinets where this space has not been sealed there is often a 1.5” to 2” wide space the height of the cabinet. For a 42U cabinet there will be 220.5 in² area left open (42 spaces x 1.75” x 1.5” between rails and side of cabinet x 2 sides = 189 in2). This is equivalent to the open area of 6.1 missing blanking panels.
Why you need to do it
Sealing the vertical plane at the face of IT equipment intakes in the cabinet is important for two main reasons:
1. To prevent exhaust air from the backs of cabinets flowing into the cold aisle and raising equipment intake temps. This condition often limits how high conditioned air supply temps can be raised and how much fan speeds can be reduced or cooling units turned off. These conditions limit the efficiency gains and release of stranded capacity that could otherwise be achieved.
2. Prevents the loss of conditioned air from the cold aisle. By holding the conditioned air in the cold aisle it is made available to cool IT equipment. This prevents bypass airflow through the cabinets, maximizing the IT load that can be effectively cooled or maximizing the reduction of cooling unit fans speeds to reduce operating cost.
As densities and the pressure to reduce operating cost increase, it becomes more and more important to improve both the effectiveness and efficiency of the cooling in data centers. Airflow management, and particularly sealing the open area of cabinets, is an important way to support these goals.
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