The last thing a network or systems administrator needs to do is feed “dirty” power to mission-critical equipment. Because power’s voltage can be affected by so many conditions, and in turn influence the health of the systems it supplies, conditioning your power supplies is crucial.
In this article, I’ll explain the concepts behind “clean power,” examine a couple of different models of power conditioners on the market, and give you some tips on what to look for when evaluating this purchase.
Computer equipment can be adversely affected by even very small changes in incoming voltage, which is commonly described with terms such as “dirty” or “polluted” power. Dirty power can cause problems in data transfer and can even damage especially sensitive system components.
“Clean” power, on the other hand, has been filtered to allow only the desired frequency to reach the connected equipment. This cleanup results in a prolonged and more reliable life for equipment served by a power conditioner.
The errant frequencies contained in dirty power often results from “noisy” devices on the circuit. The culprit frequently is motor-driven equipment, such as an air conditioning unit or elevator, that is switched on and off frequently. Electrical noise also can be introduced from sources such as nearby radio transmitters.
Almost all power disturbances, such as surges, spikes, brownouts, and blackouts, are caused by voltage fluctuations and electrical noise. Many of these occurrences are the result of lightning storms, high power demand, or other problems with the electric company, such as adjustments made at the power switching station to compensate for voltage differentials in other areas.
Cleaning up the mess
Power conditioners reside between an incoming power source and the device being protected on the electrical circuit. Power conditioners simply improve the flow of power through the unit, much in the same way network repeaters or hubs “clean up” electrical signals as they travel a network’s cabling. Hubs regenerate the signals they receive to their original form and repeat them out their other ports so that the signals reach receiving devices in a useful state. Power conditioners do the same with power supply current—“dirty” power goes in one side and “clean” power comes out the other.
A power conditioner can be used in conjunction with a UPS to provide both clean power and a fallback in the event of a power failure. In fact, some UPS units on the market today serve both purposes. In areas that frequently endure “brown outs,” or low voltage situations, a power conditioner can be important in the continuing operation of a UPS.
Many UPS units will switch to battery power when incoming power drops to as little as 100V. With certain power-conditioning units, the UPS will continue functioning without going to battery even when the incoming power browns out down to 85V-90V. However, this feature is dependent on the type of power conditioner in use. If you require this functionality, discuss it with your vendor. Some UPS units are also power conditioners, as well.
Brownouts, noise, surges, and spikes: Know the difference
Different areas suffer from different power problems, and the nature of your risk should determine the specific features you look for in a power-conditioning unit. Some of the more common problems that create dirty power are brownouts, noise, spikes, and surges. Of course, if you are in an area where blackouts or total power loss are frequent, you should seriously consider a UPS either instead of or in addition to a power conditioner.
In areas where brownouts frequently occur, having a power conditioner that is capable of handling lower-than-nominal voltages is important. In North America, the nominal input voltage for most devices is 110-120V. During a brownout, input voltage is sustained at levels much lower than this. Although generally caused by overloaded circuits, a brownout can be initiated intentionally by the power company during peak demand periods. Studies have indicated that brownouts are the number-one cause of power problems that affect computers.
Sags vs. brownouts
Situations where the voltage is reduced for a second or less are not considered brownouts but are instead called “sags.”
Like brownouts, “noise” on electrical lines can create problems for connected equipment. Line noise is technically known as Electromagnetic Interference or Radio Frequency Interference (EMI/RFI), and its results are commonly called “non-smooth” power. A normal power signal can be described by a smooth sine wave, but with EMI/RFI in the picture, this sine wave takes on some rough edges that can create problems in data transmissions.
Line noise has many causes, such as electrical motors switching on and off, lightning, radio transmitters, and even loose bolts on electrical poles. These types of problems can worsen during inclement weather and be exacerbated by solar flares. Stopping the effects of solar flares is a bit beyond our grasp right now, but at least you can specify a power conditioner that will help alleviate some problems from EMI/RFI.
Line noise is expressed in terms of decibels (dB), a standard measurement for the strength of signals. Power conditioners have a dB rating that indicates how much noise they are able to filter out. If you have measured significant noise on your incoming electrical circuits and have decided to purchase a power conditioner to address it, make sure you purchase a unit that can handle your measured noise level.
Measuring line noise
You’ll need a current probe to measure electrical noise. One of my favorite lines is from ProdynTech, which offers a wide range of probes that include handheld and in-line probes.
Surges and spikes
While many areas suffer from power voltage declines, other common problems involve upward surges and spikes in the amount of power that is coming in on a circuit. A surge is a short-term increase in incoming voltage lasting about 1/120 of a second. A spike, on the other hand, is a high-level increase in voltage that flows through the electrical system.
A surge is caused by the powerdown of an electrical motor in a device such as an air conditioner. The additional voltage that was being used to power this equipment dissipates throughout the electrical system, causing a momentary surge in voltage.
A spike, while similar to a surge, is much more severe and often is cause by a lightning strike or by the re-establishment of power after an outage. A spike can literally destroy electronic equipment. When evaluating line-conditioning equipment, be sure to consider the maximum surge rating for the unit, which is expressed in joules.
For example, say you know that your building’s air condition/heating unit is causing issues with your servers when it kicks on or off. Knowing this fact is half the battle. Attach a power meter (such as the Fluke 7 Series) to the effected server to get a measurement of the surge.
Sizing a power conditioner
Sizing a power conditioner for a specific job is critical to the health of your equipment. To successfully size a power conditioner, you need to answer these questions.
- How much equipment do you want to protect? Do you want to safeguard a few key servers or do you want a unit that is capable of protecting the entire server room? This metric will determine the output capacity of the unit that you need to purchase.
- How much electrical line noise are you experiencing? This stat will determine the dB figure that needs to be specified. Most consumer-grade power conditioners can filter anywhere from 80 dB to 100 dB of noise.
- Is your area prone to brownouts? If so, make sure that the “undervoltage,” or low voltage threshold is sufficient to your specific situation. For example, the Tripp Lite and SurgeX series of power conditioners can handle voltages as low as 87V.
- Do you often suffer major lighting strikes? No device will protect your server room from a direct strike—if that happens, it’s time to contact the insurance company. However, if lightning commonly strikes in the general area and does create a spike to your equipment, carefully consider a power conditioner’s joules rating before making a purchase. While many units can absorb a few hundred joules, some heavy-duty power conditioners are able to absorb well over a thousand.
- Do you have a UPS that protects the equipment? If so, there may be no need to invest in a separate line conditioner. Check your UPS specifications to see if the system also performs this function. Many do.
How you want to distribute conditioned power is also a key ingredient in this equation. Certain units (such as the LCR 2400 Line Conditioner from Tripp Lite) can fit in a rack with servers. Some power conditioners (such as the UPPI Pioneer Line Conditioner) are placed in the power distribution line to a server room so that there is no need to use separate units for racks of servers. Others (such as the APC SurgeArrest Performance) are designed to protect one or two key pieces of equipment.
Number of outlets does not equal capacity
Don’t make the mistake of equating a conditioner’s number of outlets with its overall capacity. Some units offer a large number of outlets, but that’s no guarantee that the power capacity of the unit can sustain a fully loaded configuration. You must check the electrical rating of the equipment you intend to attach and match it up against the maximum output of the power conditioner.
There are two types of placements to consider here. The first is to place the power conditioner before the UPS, which is stationed in the circuit before the protected equipment. In this scenario, the power conditioner protects the UPS from having to switch to battery for unnecessary reasons, such as spikes and surges. The second is to place the power conditioner after the UPS, which makes sure the feed coming from the UPS is clean. The former protects the UPS, which protects the equipment; the latter protects the equipment from possible damage from the UPS.
A look at some power conditioners
To get an idea of how the features of power-condition units can vary, let’s take an in-depth look at three power conditioners. This is not meant to be a review or endorsement of these units, but simply an illustration of what to look for when shopping for a power conditioner.
APC Line-R 1250VA and 600VA automatic voltage regulators
APC is one of the bigger names in power equipment when it comes to IT shops. In addition to its line of UPS equipment, APC also offers various models of the Line-R power-conditioning unit. Available in 1250VA and 600VA varieties, APC also offers these units in 120V varieties to serve North America and Latin America and a 230V model for Africa, Europe, and the Middle East.
Table A shows the per-unit features for the 1250VA and 600VA. Both units supply overvoltage and undervoltage protection, as well as four outlets.
|APC Line-R 600VA
|APC Line-R 1250VA
|APC part number
|Number of outlets
|Lifetime up to $25,000
|Lifetime up $25,000
|50 or 60 Hz
|50 or 60 Hz
|600VA (or 600W)
|1250VA (or 1250W)
|Average street price
Both the 1250VA and the 600VA sport diagnostic LEDs that provide at-a-glance updates on the quality of the incoming voltage as well as an alarm that sounds when the unit experiences a situation it cannot correct.
These two power conditioners would be suitable for one to four servers, depending on power requirements.
Tripp Lite line conditioners
Another leading vendor in IT power equipment, Tripp Lite, markets a complete line of power conditioners, ranging from a series of desktop/tower units to rack-mount and wall-mounted units. Their lineup ranges in capacity from 600VA to 2400VA—not enough to run an entire server farm, but enough to support a pretty significant equipment load. Table B shows a matrix with a list of features present in all of the Tripp Lite power-conditioning products. Tripp Lite’s rack-mountable 2400W unit is impressive in that it includes 12 power outlets, which could support a substantial server group.
Across the board, Tripp Lite’s products can support incoming voltage ranges from as low as 87V up to 140V, and the company’s higher-end products have impressive support for surges, with a capacity of up to 1,440 joules. Ranging in price from about $65 for the LS600 to just under $300 for the LCR2400 rack-mount unit, these devices are inexpensive ways to help protect the valuable investment made in IT hardware.
While APC and Tripp Lite offer a wide array of products, some users will demand more capacity beyond the 2400W ceiling. For them, there is UPPI, which has products that pick up where Tripp Lite leaves off. With units ranging in capacity from 4,000VA to 10,000VA, this product line can meet many needs.
The UPPI units are focused on commercial, heavy-duty applications. While a Tripp Lite or APC line conditioner may support a server or group of servers, the UPPI choice would be better suited to serving an entire server room instead.
In fact, some of the UPPI units do not feature traditional power cords. Instead, they are hard-wired to the circuit panel, and output receptacles on the unit can be customized to meet exact requirements. Featuring an input voltage range anywhere from 120V to 240V (hardwired to the circuit panel), these units can support 30A to 70A of current, depending on the model and input voltage. Their voltage thresholds range from 20 percent below nominal voltage to 15 percent above incoming nominal voltage.
Even the size of these units is indicative of their ability. While the APC and Tripp Lite units can be carried around and rack mounted, you would be hard-pressed to carry a UPPI unit to the next room, since they weigh in the range of 440 to 860 pounds.
Because of the number of ways in which these units can be customized, citing average street prices and typical configurations is not feasible. You can expect to spend much more for one of these units than for smaller APC or Tripp Lite units, but remember that one of these conditioners, fully configured, would be capable of supporting almost 40 Dell PowerEdge 1650 servers. And there’s something to be said for being able to place the unit on the incoming power line to the server room rather than needing to purchase smaller units for individual racks.
A vital part of the circuit
While a power conditioner does not replace a UPS, it’s an important component to consider when designing a power infrastructure for a server room or data center. Most importantly, evaluate your own power quality needs before you start shopping for a conditioner, and make sure the unit’s capabilities match your criteria.
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