Online/double-conversion UPS economy/high efficiency modes?

William Herrin bill at
Thu Dec 6 20:49:51 UTC 2012

Hi folks,

I'm looking at several brands of rackmount 3kva double-conversion
UPSes, such as Tripp Lite and Eaton Powerware. I'm specifically
looking for something that will work as a line-interactive UPS until
the power starts to misbehave and will then switch to
double-conversion mode until a while after the last power bump.

Basically I want the best of both worlds: save money on my power bill
most of the time (double-conversion UPSes generally waste 10%-15% of
the consumed kilowatt hours) but switch to nice clean
double-conversion when the storms roll through and the power gets

Here's where I'm looking for help: the vendor web sites have scanty
details about how the UPSes behave in their high efficiency modes. I'm
hoping folks here have used some of the UPSes with this feature and
can offer feedback.

When does the UPS decide to switch to double-conversion? When does it
decide to switch back? Are the options tunable? Through what
interface? Can I write software that monitors a weather report and
sends an SNMP message to switch the UPS to double conversion mode
ahead of a storm?

Eaton's 9130 says "On the High Efficiency setting, the UPS operates
normally on Bypass, transfers to inverter in less than 10 ms when
utility fails, and transfers back to Bypass in 1 minute after utility
returns. The indicator illuminates when the UPS transfers to Bypass."

Tripp Lite's SU3000RTXL3U only says "If the UPS has been placed into
Economy Mode (available on select UPS systems), it configures an
online UPS to function as a switching UPS. When the UPS system is in
Economy Mode, it operates at increased efficiency while AC utility
power is available (within +/- 10% nominal) and switches to battery
power if AC utility power is interrupted."

What others should I consider? Can anyone offer details?


William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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