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

Thu Dec 6 22:19:31 UTC 2012

On 12/6/12 12:49 PM, William Herrin wrote:
> 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
> rough.
> 
> 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."
> http://lit.powerware.com/ll_download.asp?file=Eaton%209130%20UPS.pdf
> 

I have a 700VA 9130 rackmount that I recently bought to give it an eval
run (although the first was a dud). There is a 3kVA model. For my small
load it reports a PF of 0.91 online.

It is selectable between normal and high efficiency mode through the
front panel. I would assume the tolerance settings in there related to
bypass availability would trigger online mode. If it does kick over to
online from high efficiency bypass it'll stay there for a minute to
watch for stability before going back.

The network card (Network Card-MS) is extremely sparse in being able to
configure it remotely. It's mainly just for status. It does not have an
option in the web interface to toggle the mode or change the bypass
tolerance settings, however, there is a MIB object for "power strategy"
that says it's read-write but I haven't tried writing to it yet. I guess
I can try it and report back.

~Seth