Use these helpful tips to choose a midrange UPS - Technology Information

Communications News, June, 2001 by Ron J. Kovac, Julie A. Geeting

Network administrators have a variety of selections to protect equipment.

An uninterruptible power supply (UPS)--hardware attached between computer equipment and the electrical power supply--can encompass everything from a single PC to network servers to complete data centers. UPSs plug into computer equipment or can be hardwired into the device. UPSs regulate the flow of electricity from the wall outlet to the attached computer equipment, absorb power surges and power spikes, and account for low power situations.

These systems provide protection to computer equipment from electrical spikes--momentary, unpredictable increases in the voltage--while also maintaining power with internal battery packs in brownout and blackout situations. The battery pack also protects data from loss. These power supplies give users, or the system itself, enough time to save information, then shut down the system safely. Electrical anomalies account for about 87% of all power disturbances. A standard surge suppressor will not protect computer equipment in any of these situations.

The average time a UPS provides power backup is five to 15 minutes for medium to large units. Larger UPSs allow network administrators to monitor everything from the environment, which includes temperature and moisture, to system warnings that will send notifications of a system failure.

The purpose of this research is three-fold:

* Identify midsize UPS characteristics for use in a data center environment.

* Define the major vendors who make equipment in the 2 kVA to 5 kVA range.

* Compare and contrast these UPSs based on the defined target criteria.

A UPS, for this purpose, was defined as a unit that continues to provide power in the event of any type of power failure or anomaly. The next step was to delineate between the various types of UPSs. The selected 2 kVA to 5 kVA range encompasses the midrange sizes of UPSs, those that could protect three or four network servers, their monitors and peripheral equipment.

Next, UPS vendors producing units that fit the criteria were selected. Comparisons were made on a basis of criteria deemed as important for an enterprise to know. As can be expected, each vendor listed the criteria differently and direct comparisons were not always obvious. Contacting vendors and further research allowed for the clarification of these issues.

When purchasing a UPS, the issues and criteria to consider include:

Sizing. A good rule of thumb to follow when sizing UPSs is to add the total kVA ratings of all the devices that will be protected and add 25%. This gives a baseline total from which to start. For example, if protecting a small server that has a rating of 2200 VA and a monitor that has a rating of 300 VA, the total device rating is 2500 VA. Add 25% for a total requirement of 3.125 VA, or 3.125 kVA. Be sure to plan for any anticipated growth. In addition, the UPS selected should provide the proper utility connections (120V to 240V), and have enough outlets to support the number of devices being attached.

Backup time. How much time will be needed for the device to operate on battery power? Do you expect a blackout or brownout? Does the UPS selected provide support for additional batteries to increase runtime? If so, how many can be added?

Level of protection. Three basic types of UPS offer different levels of protection: standby, line interactive and online topologies. The standby topology system will switch between utility and battery power when there is a blackout situation.

The standby system leaves a brief switching interval (two to 10 milliseconds), which is undetectable to attached equipment. A line interactive UPS provides additional power protection in blackout, as well as brownout and surge situations. This type of system will monitor the power supply on a continuous basis, allowing the UPS to maintain the integrity of the power coming from the outlet. The last type of UPS topology is online, which converts high-voltage AC power from the outlet to low-voltage DC power, then back to AC to supply it to the devices attached to the UPS. The batteries for this type of UPS are always online, so there is virtually no downtime during a blackout situation.

Manageability. Most UPSs include software that allows management of the UPS itself, as well as the attached equipment. Line-interactive and online UPSs usually provide this option, but standby UPSs do not give the user the option of choosing the type of shutdown that will occur.

Uninterruptible power supplies provide a good measure of data insurance by providing clean power to the equipment on which the data resides. Additionally, UPSs provide an increased measure of reliability for computers and connected networks during a power outage. Ask the right questions, compare the product specifications in the accompanying chart, and ensure that your enterprise protects its network from power outages, surges and dirty power.