Uninterruptible Power Supplies
June 5, 2011Options
· Standby—guards against brownouts and blackouts by puffing power from the battery
· Line-interactive—provides battery power during blackouts and protects against surges and brownouts with an inverter for automatic voltage regulation
· On-line—isolates equipment from any type of power disturbance by converting incoming power from AC to DC and then back to AC before exiting the UPS
Why Buy?
Power loss, among the leading causes of business disruption, not only brings operations to a halt without warning, it can jeopardize worksite safety, impair security systems, damage equipment, and lose data Uninterruptible power supplies (UPSs) ensure power continuity while traditional electrical power sources are down.
What To Look For
1) Products listed with UL in the United States, CSA in Canada, CE and TIN in Europe
2) Management software that is compatible with multiple UPSs at various locations
3) Vendor-offered power analysis
4) Battery management system to increase battery life, run time
5) Adjustable option switches that allow users to tailor voltage transfer levels to site specifications, disable alarms, and change ‘low battery” warning settings
6) Customizable warning methods, such as paging and network broadcast messages
7) Site wiring fault indicators and front-panel indicators, including “low battery,” “replace battery,” and load meter
8. Communications that fit user applications, such as RS232 and contact closures
9) Tight output voltage regulation
10) Ability to correct for surges and sags
11) Superior noise attenuation addressing load and line-generated harmonics
12) Versatile and sufficient output connections
13) Unattended shutdown software and bypass system
14) Magnetic isolation
15) Optional run-time availability
16) Sine wave output on battery
17) Vendors with engineering capabilities to meet special needs
18) Vendors equipped to respond in crisis situations and who offer 24-hour field service
COST CONSIDERATIONS
A detailed cost analysis will often reveal bidden expenses. Then adding up costs, consider the following:
1) Price ranges are substantial. A single-station UPS providing five to 10 minutes of backup power will range from $100 to $160. UPSs with extended run time can cost from $800 to $2000. On-line tips can cost up to 20 percent more for comparable sizes.
2) Investing in a fully featured unit now may save on expenses of future add-ons and upgrades later.
3) Determine if installation is included in the purchase price.
BE PREPARED
In order to bid for your business, vendors will want to know:
1) Specific application, installation location—office or industrial
2) Input / output voltage requirements and KVA rating
3) Battery time desired
4) Load requirements; what equipment will be supported by the UPS and how much power does it draw.
5) Look for this information on equipment labels. Load priorities; what’s mission-critical?
6) Aggregate electrical load can be obtained by taking ammeter readings of electrical distribution boxes at
7) Peak operating times, from listings on electrical distribution boxes, or as peak demand readings on your electrical bil
KEY QUESTIONS TO ASK POTENTIAL VENDORS
1) What is the unit’s run time?
2) What is its voltage range?
3) Are visual and audible alarms included?
4) What are its battery management capabilities?
5) Is noise filtering technology employed?
6) Is the UPS compatible with power management software?
7) Is the UPS generator-compatible?
8. Do you offer battery and preventative maintenance?
9) Do you employ factory-trained field service engineers?
10) Do you offer dedicated service?
11) Has the unit met IEEE 587 or IEC 664 test requirements for surge suppression?
12) Does the unit include modem, fax, and network protection to safeguard from surges coming through phone lines or network data lines?
13) Will you repair or replace equipment damaged due to a UPS malfunction?14) What are the specifics of the warranty, extended warranty?
KEY QUESTIONS TO ASK VENDOR REFERENCES
1) Was the unit delivered on time?
2) Was installation easy, quick?
3) Are you satisfied with performance, service?
4) Provider and product strengths / weaknesses?
5) Any experiences with activation?
a. Results?
6) Any experiences with testing?
a. Results?
7) How similar to my own are your company’s power needs?
8. Why was this vendor/product chosen?
a. Were others considered?
9) What did the selection process entail?
10) In retrospect, were you either over- or under-sold?
BUYER BEWARE
1) A UPS should supply the load with an ideal sine wave or stepped sine wave output. Square sine waves can damage loads or cause malfunctions.
2) Determine the transfer time when switching to battery power. Although most UPSs have transfer times of 2 milliseconds or less, transfer time of even half a second can cause computer failure.
3) In order to get extended battery run time, are you over-buying in terms of KVA?
4) Don’t mistake TVSS surge suppression for power conditioning.
WHAT NEXT?
1) Involve IT support as well as appropriate operations and facilities maintenance personnel in equipment evaluation and selection
2) Create a features matrix accounting for all possible offerings, for at-a-glance comparison of all models being considered
3) After pre-qualifying equipment, request a demonstration
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