Sizing Up Your Data Center Power Requirements

Capacity planning can be tricky given all the factors that come into play. In order to size the UPS and cooling requirements, the power load of all the IT equipment must first be determined. The nameplate ratings found on the equipment are notoriously high because these power supplies are rated while running at 100% and are typically designed to work with other products or future generations of a device. Some equipment manufacturers provide power calculators for various configurations of their products. A more accurate method is to trend the load by monitoring outlet-level power utilization over time and at various degrees of utilization. This information can be used to extrapolate future requirements for both the near term and future growth three to four years down the road. A recent article in SeachDataCenter.com covers these and other issues to consider.

Other factors to consider are where opportunities exist to increase power efficiency such as the advantages of using 208V, 3-phase power or possibly deploying 240V/415V. Server Technology has published three white papers covering these topics:

• Measuring Power and Efficiency
• Planning, Implementing and Application of Cabinet Power Distribution Units
• Power Efficiency Gains by Deploying 415 VAC Power Distribution in North American Data Centers

Comments

[David Sonner]

I am intrigued by all of the discussion related to moving toward 415/240 AC power distribution architectures. Without a doubt there is a significant advantage in efficiency at the server power supply level when the source voltage is raised from the typical 208V to 240V level, and even more dramatically if you are still in a 120V world. What is of particular interest is the move to eliminate transformers between the UPS (even transformer-less UPS units!). While eliminating transformers in the UPS and distribution system does save on efficiency, it comes at the risk of eliminating AC galvanic isolation for the ever-so-critical IT load. It’s a question of robustness versus efficiency. In the transformer-less UPS world, distributing 415/240 directly to the racks may put your loads a diode junction failure away from as much as 800VDC in some cases. There are many other risks as well. It seems a best practice would be to incorporate a system that has both advantages of higher AC voltage, along with the benefits of transformer load isolation.

[Dave Cooley]

The plot may thicken more as many organizations and groups like the Data Center Pulse are advocating taking 480 V directly to the cabinet as three phase power and distributing it to the servers as 277 V single phase as another step in increasing efficiency. This was in the top 10 wish list of the Data Center Pulse and I am sure on the minds of others as more efficient power distribution solutions are being explored.

[David Sonner]

I agree, and the opportunity is real, but I believe it will require the OEM power supply base to make some significant changes in designs for component selections to be applied at the higher voltages. The good news is that the power infrastructure industry in the Americas is ready and able to support 480/277 systems with standard, off-the-shelf systems and not move toward a standard with which folks are less familiar.