Backup Power Systems

By Peter Lyle DeHaan, PhD

Author Peter Lyle DeHaan

Most call centers know the importance of having a good and reliable backup power source. Unfortunately not all centers have taken steps to obtain that protection or to ensure that it is adequate and properly maintained. Given rolling blackouts in California, the recent unprecedented outage affecting most of the Northeast United States reaching into Canada, and the interruptions that generally follow hurricanes, there is ample reason to move backup power to the top of the priority list. Add to this possible quality issues with utility power, such as brownouts, sags, surges, spikes, and so forth (see the Power Glossary for an explanation), the need to be covered with backup power is all the more critical.

“During the hurricane, the power was real dirty,” stated Steve Kenny, owner of The Best Answer, in Ocean City, MD “and many people lost power or their power was intermittent. Our service kept running because of the UPS backups and our propane generator. This gave us clean, uninterrupted power while everyone else lost power.” One of their clients, a home health company, was without power. “We were able to answer their calls, dispatch oxygen, and medicine to the nurses, and act as the clearing house for them. Their competitor was without power, too, and [our client] picked up a few new customers because of our reliability.” With good, reliable backup power systems, you too can gain new business and better serve existing clients.

Whether your center needs to install backup power for the first time, add more capacity, or replace aging systems there is a general strategy to follow. Use UPS systems for immediate, short-term protection supported by electrical generators for long-term outages.

UPS for short-term outages and problems: Uninterruptible Power Supplies (UPS) provide a quick source of power for short durations. Since most power outages or problems last less than two hours, UPSs are the best first line of defense. In general, a UPS takes DC power from batteries and converts it into the AC power needed to run call center switches, computers, and networks. The more batteries, the longer power can be supplied but at a greater cost.

There are different types of UPS systems, which produce different qualities of voltage. While manufacturers may use different terminology, UPS fall into two general categories. The first are those that run power through them, conditioning and filtering it all the time. When there is a problem with the utility power, these UPSs are already on the job working. The second type monitors the line, but does not filter or condition it. At the sign of a problem, they turn on, take over, and provide power until the utility power is restored and stable.

Both approaches have their strengths and weaknesses. If you have any doubt about which is best for you, have an in-depth discussion with your vendor, preferably one that sells both kinds.

Also, the quality of the power provided by UPS systems varies. More advanced systems produce a pure waveform, called a sine wave. Simpler and more basic units may have a “square-wave” or some other non-sinusoidal output. For some equipment, this won’t matter, while for other things, such as sensitive electronics, this could present a problem or shorten the life span of the equipment. When considering both the style of UPS and the type of output generated, there are cost-performance issues to be carefully weighed.

When installing UPS systems, there are three strategies for consideration: The first, and historically most common, approach is a single large UPS system, in a central location. It will typically be in the phone or computer room and will supply power to all critical systems, as well as a requisite number of agent stations and perhaps some minimal overhead lighting. The length of run time is determined by the number of batteries and the load, or amount of current that the devices plugged into it require. The advantage of a single centralized system is that there is a common maintenance site, while the disadvantage is that it provides a single point of failure. Also, an electrician is generally needed to install these larger units and rewire the circuits that need protection.

The second methodology is the distributed approach. Here, multiple smaller UPSs are installed throughout the call center and equipment rooms, at the point of need, to provide back up power to a small number of devices or even a single unit. Often, one or two agent stations will be serviced by one small UPS. The advantages are that they are easy to install (just plug them into an outlet and plug the computers into them) and there is no single point of failure. The disadvantages are that with multiple units, maintenance is often harder to track and more time consuming. Smaller UPS units can be found from a variety of sources. “Amazingly, Best Buy has a large selection of individual usage UPSs,” stated Thomas D. Larvin, President, Creative Switching Designs, Inc. “They have saved us numerous times during power fluctuations, [which are] common here in Houston.”

The third strategy is the combination approach. Since each UPS system is rated for a certain range of load (the amount of power it can supply) as call centers grow and more things are connected to a main UPS, often its rating can be exceeded. This can cause a UPS to underperform or to not work at all. Rather than discard an existing system that otherwise is in fine working condition and replacing it with something bigger and more expensive, an option is to supplement it with secondary UPS or a number smaller distributed units. In this way the original investment is maintained, while increasing the overall power protection.

Generators for long-term protections: Once the batteries in a UPS run down, it can no longer power the equipment that is connected to it, so it too shuts down. For this reason, most modern call centers also have a generator to cover power needs for longer durations. Generators are essentially an engine, powered by gasoline, natural gas, or propane, which produces an AC voltage, similar to the electrical utility. Since they are an engine, they must be started and the voltage output must be given time to stabilize. This generally takes two to five minutes to stabilize.

Generators are run in parallel to the utility company lines, but are not connected to them. To use a generator’s power, the power company must be disconnected and then the generator connected. This sounds complicated, but it is easily accomplished with a transfer switch. A transfer switch, which must be installed by an electrician, can be either manual or automatic. While manual switches are inexpensive, someone must activate it and know how and when to do so. In the midst of a power outage, this seemingly simple task can introduce some unexpected problems. An automatic transfer switch handles all of this without human intervention. It is recommended for all but the most basic (and non-critical) installations.

The question of which generator fuel source is ideal can be a perplexing issue, but the answer is simple. Merely find out which fuel source is the most readily available and practical in your area.

Too many people have made the mistake of buying a generator that is too small. Most experts use the rule of thumb that your generator should have three times the capacity of your UPS and any other non-UPS loads that it needs to handle. The reason for this is so that the generator can handle the peak current requirements when devices cycle up and when the generator first comes on line, switching from no load to full load.

Maintenance and testing: UPSs and generators are not pieces of equipment that you buy, install, and then forget about. If you neglect them, they will fail, but you won’t know until you need them because of a power outage. Then, you are no better off than if you hadn’t purchased them in the first place.

For UPSs, the primary maintenance issue is to periodically replace the batteries. Closely follow the manufacturers’ recommendations on this. Yes, you may end up replacing batteries that still have some life left in them, but you don’t want them to fail when you need them most. Two to five years are commonly recommended intervals, even if you have never needed the UPS. It is also good to periodically test UPSs to make sure they do in fact work. Schedule testing during a non-critical time, so that if there is a problem, the impact is minimal.

Generators, just like cars, need to have their oil changed, filters cleaned or replaced, and battery periodically replaced. Again, adhere to the manufacturer’s recommended maintenance schedule. The maximum time between maintenance is annually, even if the generator has not been used. Maintenance needs to be done more frequently with heavy usage.

Many generators come with an “exerciser” module that will automatically start the generator each week and let it run for about 10 to 20 minutes. If the generator doesn’t start, runs poorly, or produces inadequate output, a warning will be produced. This allows users to seek the necessary repairs before the generator is needed for a real power outage.

(Also see Battery Recycling, Backup Power Vendors, and Power Glossary.)

Peter Lyle DeHaan, PhD, is the publisher and editor-in-chief of Connections Magazine. He’s a passionate wordsmith whose goal is to change the world one word at a time.  Read more of his articles at

[From Connection MagazineNovember 2003]

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