Stand By, Line Interactive and Online UPSs

There are 3 types of UPSs: Stand By, Line Interactive and Online. Different manufacturers designate them differently in their product lines.  For example, Powerware calls them Level 3, Level 5 or Level 9 protection.

STAND BY UPS (also called Off Line UPS)
This basic model does just what its category name implies.  It just sits there ignoring everything that's going on with your power, except a complete power outage.  The cheapest- of-the-cheap stand by units will do only that, turn on when the power goes out. More expensive units may also offer some surge protection, possibly even some automatic voltage regulation (AVR).  A stand by UPS can take as long as 35 to 45 milliseconds to switch over to battery power.  They are the least protective of attached equipment and should only be used with equipment that is not all that important, and that may also be attached to a surge protector.

Examples of Stand By (or Off Line) UPSs:
     APC BackUPS
     Powerware units beginning with the number 3
     Liebert PowerSure PST and PSP lines

LINE INTERACTIVE UPS
The next higher level of UPS protection is line interactive.  These units (with the possible exception of "off brands") will offer a quicker response time (2 to 10 milliseconds to go to battery) and have some measure of automatic voltage regulation (AVR) and surge suppression.  Lower-priced units will put out a stepped, or modified, sine wave, but higher-priced units will produce a pure sine wave.  Also, higher end units will go to battery in a brown-out (to boost the voltage) and in an over-voltage situation (to lower or "buck" the voltage). The best line interactive units will perform buck and boost without having to go to battery and thus extend your UPS's battery life.  Some line interactive units also offer a settable range of voltages they'll tolerate before going to battery.

Examples of Line Interactive UPSs:
     APC SmartUPS
     Powerware units beginning with the number 5
     Liebert PowerSure PSA and PSI lines

ONLINE UPS
The highest level of UPS protection is online.  Online units take the incoming voltage, rectify it and downconvert it to the battery voltage of the UPS, filter it, reinvert it and upconvert it to the appropriate output voltage for the unit. The output voltage is always rock-steady and the sine wave is always pure.  Nothing bad (power-wise) gets through an online UPS.  In addition, there is ZERO transfer time to go from failed line voltage to battery power.  If power fails, you're on battery with no delay. Online units also tend to take better care of their batteries, so you'll typically get a year or two more lifespan from them over the other types of UPSs.

Examples of Online UPSs:
     APC SmartUPS RT Series, Symmetra
     Powerware units beginning with the number 9
     Liebert GXT and GXT2 lines, Nfinity
     Most 3 phase UPSs are online units, regardless of size or manufacturer
 

As with most everything else in life, so with UPSs, you get the level of protection that you pay for. For absolute, non-fail, ultimate protection of your equipment and data, spend a little more and get an online UPS. Because of its non-varying output, the electronics you attach to it will last longer, whatever they are.

We hope this page has helped enlighten you to the goings-on in the UPS world.  If you have any questions or comments please call us at 800-255-5545 or email: info@4upsbattery.com