The Importance of Balancing Data Center Power Consumption

Jack Vonich is VP of Sales for Instor Solutions.

How to effectively balance the power load in data centers is an issue that every data center manager is familiar with. When done correctly, a properly balanced data center helps to secure uptime and is often an important avenue for the facility to utilize extra power capacity. When improperly balanced, available power can become stranded, and the chance of damage to vital infrastructure increases. Taking the time to optimize power distribution when installing or refitting a data center is well worth the effort and is another crucial step toward maximizing its performance.

To help avoid stranding power, we can look at the following example (power coming into data centers is measured as either X + Y + Z + Gr or X + Y + Z + Gr + N). In this simplified model, we’re working with three-phase power which is broken into groups of two phases for each outlet powering the individual devises on the power strip.

If the devices are consistently plugged into the same group in each rack then one phase may be more heavily loaded compared to the two others.

In this hypothetical scenario, if 100 devices (for our example let’s use server racks) were loaded this way and 1000Amps were the maximum phase load, there would be a significant amount of stranded capacity in the data center once Y hits the maximum load:

1000Amps = Y

800Amps = X

200Amps = Z

An additional 100 racks could be added to the XZ phase groups to potentially balance the load more effectively, which would be a fast and tempting solution. However, even making this change would not produce an optimally balanced data center as it would result in:

1000Amps = Y

1000Amps = X

400Amps = Z

While a step in the right direction, this configuration only utilizes approximately 500 kilowatts of power out of a maximum 600 kilowatts in the data center, stranding 100 kilowatts or 16 percent of available power. Clearly, improvements can be made.

To properly distribute the power in our example, the load must be spread across all phases, providing the much needed balance that the previous configuration was lacking, resulting in an increase in available capacity.

Now, if those same 100 server racks have the power distributed across the three-phase pairs, the load becomes more balanced and capacity is utilized much more effectively:

600Amps = Y

800Amps = X

600Amps = Z

The extra benefit of this properly balanced power load is that an additional 250 devices can be added to the power strip: 50 on the XY group, 50 on the XZ group, and 150 devices on the ZY group. This results in:

50 devices added to XY

700Amps = Y

900Amps = X

600Amps = Z

50 devices added to XZ

700Amps = Y

1000Amps = X

700Amps = Z

150 devices added to YZ

1000Amps = Y

1000Amps = X

1000Amps = Z

Most importantly, with the power load now optimally balanced, all of the available energy (600 kilowatts) is being used to run data center equipment. The problem of stranded power has been corrected and the maximum potential of the data center and its many pieces of equipment is realized.

Even when a balanced power load has been achieved, it is important to remain vigilant as new changes to the data center are made. To help avoid future power balance issues, engineers need to understand the circuit capacities of their data centers and design rack power loads to fall within the de-rated power capacities. Whenever possible, they should also use outlet phase alternating power strips as well as rack power strips containing an LED display that provides readings on the power load (the latter allows staff to easily adjust into which phases each device is plugged). Finally, employing a basic DCIM tool to monitor loads and balancing with IP enabled power strips or Branch Circuit Monitoring can also be very helpful to discover power load issues as they are occurring. As with all technology, it pays to be proactive rather than reactive, and power load balancing in the data center is no exception.

Industry Perspectives is a content channel at Data Center Knowledge highlighting thought leadership in the data center arena. See our guidelines and submission process for information on participating. View previously published Industry Perspectives in our Knowledge Library.