Four questions to ask when powering IT at the network edge

June 1, 2016
Asking and answering the questions that underscore the UPS's importance

By Brian Kennedy, Emerson Network Power

Although the title of this article cites four questions, let’s start with a free question. Consider it a bonus. This one sounds simple, but trust me-it’s important. Here you go …

How do you define the network edge?

Is the edge of your network an IT-heavy collection of computing assets in bank branches or doctors’ offices? Or does it lean more toward the traditional telecom definition, access sites at the edge of a telco network that increasingly include more and more IT equipment?

It’s an important question, because the power profiles are so different. Those computer rooms in your average doctor’s office contain IT equipment powered by traditional AC power. Telecom sites operate off of DC power, the accepted norm in that industry virtually since Alexander Graham Bell rang up Mr. Watson for the first time 150 years ago. There’s a fundamental difference.

For the purpose of this piece, we’re going to focus primarily on the IT edge, but we’ll touch on some telecom thoughts as well. So let’s start with the question you’re dying to ask, since you’re probably going to scroll through until you find it anyway.

1. What’s the best power solution for your network edge application?

The obvious answer is: It’s complicated. Start with this: There are three core options for these applications-single-phase AC UPS systems, small three-phase AC UPS systems or DC power. As mentioned earlier, DC power is the default choice in telecom installations and has a small (but growing) presence in the IT space. Let’s focus on the AC options.

Most three-phase AC UPS systems (and DC power systems, for the record) have built-in redundancy and are scalable-you can add power modules to increase the capacity if needed. Single-phase AC is a simpler, more cost-effective option that sometimes lacks redundancy or any real scalability. If your load increases, you’re going to have to add another UPS unless you’ve thought ahead and purchased a scalable single-phase UPS.

So the answer to this question is: It depends. Which leads up to our next question.

2. How critical are your computing needs and data at the edge?

There was a time, probably not too long ago, when the kneejerk answer to this question would be, “Not that critical.” Edge sites were IT closets with a server and enough on-site computing power to manage the needs of an average office. They were at the edge, but they weren’t really part of the network. They may not look all that different today, but they absolutely are part of the network-and that changes everything.

Today most edge locations are a single piece of a distributed data center architecture that can include hundreds of sites. Those sites are increasing in importance as the network becomes more intelligent and connected. Edge sites track personal finance changes and irregularities, unusual privacy-related activity, traffic patterns and shopping trends, provide storage and access to medical records, and perform rapid data analysis that triggers real-time response either at the site or from the central data center. Like everything data center-related, the edge is an increasingly critical business asset.

Consider this: According to the latest Ponemon Institute report on the cost of data center outages (commissioned by Emerson Network Power), the average total cost per minute of an unplanned outage increased from $5,617 in 2010 to $7,908 in 2013 to $8,851 in the report released earlier this year. That’s all data centers-not just the edge-but you get the point. Don’t be so quick to dismiss the criticality of any IT systems, even those at the edge.

The Ponemon study also found that UPS system failure is the number-one cause of unplanned data center outages, accounting for one-quarter of all such events. With that in mind, if the answer to this question is “fairly critical,” then redundancy should be a priority. And that means a UPS designed for providing redundancy should be considered, whether single-phase or three-phase AC power is required.

Having said all that, there still are plenty of edge locations where IT systems are important, but not critical and power requirements are typically small in nature, say under 5kVA. In those environments, you probably could get by with a non-redundant, non-scalable single-phase AC UPS and live with occasional-but still uncommon-outages.

3. What’s your footprint?

In new builds you have a little more flexibility to design and build around whatever power system you choose, but in any existing facility you will need to work within the established space. It shouldn’t be the deciding factor in selecting equipment, but it’s a real, practical issue.

As mentioned earlier, if you choose a single-phase UPS and think there is any possibility you will need to add capacity later, you will need to order a redundant UPS, or start small with a less-expensive non-redundant model and replace that system with a larger one when your requirements grow. That’s one of the reasons that three-phase systems typically present more flexibility and scalability, allowing you to go from 15 to 45 kVA, for example, simply by sliding in additional modules. Some scalable three-phase systems can even grow to 200 kVA in typical voltages such as 208 volts.

Space restrictions do not necessarily rule out any specific type of power system, but it may make integrated IT and infrastructure systems an appealing option. These systems integrate computing, power and cooling (if necessary) together into a single unit with a much smaller footprint than required if the same pieces are deployed separately.

And space isn’t the only argument for integration. These systems simplify what can be complex environments, factory-assembling whole units that are virtually plug-and-play. Not all vendors assemble their integrated systems at the factory; some ship the frame and various parts separately and require on-site assembly. That slows the process and eliminates one of the benefits of assembly at the factory-reduced risk by way of testing the fully assembled system prior to shipping.

Along with footprint, think about the location of the IT equipment. When we evaluated a site experiencing unusually short UPS battery life, we found the IT equipment was located close to the elevators and both were being powered on the same circuit, which can happen in some leased office spaces. The UPS was forced to handle repeated power sags whenever the elevator was used. Those sags drained the batteries to the point they couldn’t deliver the backup power the site needed. Separating the two pieces of equipment from the circuit took care of the problem.

4. What else should I know?

OK, this is a cheat. We promised you four questions, we’ve already thrown in a bonus question, and there’s still more you need to consider. So we’re throwing a couple of extra answers under this admittedly broad question.

Let’s start with efficiency. This is an important topic for edge sites because of volume. It’s not uncommon for a large bank or healthcare system to have 300 or 400 edge deployments. With those kinds of numbers, even modest efficiency gains at each site can add up to something substantial.

The most common tool to gain energy efficiency is proper UPS sizing, so that the load on the UPS is not so small that the unit operates inefficiently. Another widespread approach for improving energy efficiency in either single-phase or three-phase UPS systems is eco-mode. This means you’re taking the UPS out of double conversion mode and running power through the bypass circuit. Eco-mode can improve efficiency by anywhere from 4 to 8 percent, which can add up quickly across 400 sites. We should mention that DC systems also offer eco-mode, but it’s achieved differently. DC power systems use several rectifiers, and in eco-mode one or more of those rectifiers goes offline. Larger three-phase UPS systems, incidentally, can operate in this manner as well, but are beyond the scope of this network-edge article.

This feels like a good time to mention the importance of understanding any UPS system’s true capacity. With older generations of power equipment, you typically did not know the system’s power factor, which meant you really didn’t know the capacity of the UPS. The system might have been rated for 20 kW but had a power factor of just 0.8. That meant it really provided only 80 percent of its rating. Perform your due diligence before purchasing a UPS and don’t rely on advertised capacity. Look at the power factor as well and check out the system’s efficiency rating while you’re at it. A UPS with “unity” power factor, or 1.0 power factor, provides 100 percent of its rated capacity and should be the product you select in order to get the most bang for your buck.

One more thing. Most of today’s UPS systems-and even many power strips, on the extreme end of the power spectrum-have increased visibility, intelligence, monitoring and management capabilities. These technologies enable everything from battery monitoring to remote control (some single-phase UPS systems can be rebooted remotely, for example) to seamless integration with third-party building and IT monitoring systems. This is important in edge environments, where there often isn’t a dedicated IT professional available to service or maintain equipment. Remote service and management can save a lot of road trips for an organization’s IT team. Some UPS products even have the capability to communicate using two protocols simultaneously, offering the utmost in flexibility and visibility across multiple monitoring systems.

Brian Kennedy is senior product marketing manager with Emerson Network Power (

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