UPS backup musings

[Igor Gueths]

Hi Greg,
years ago I purchased an APC Back-UPS RS-1500, max output is around 875W/1500VA
and it will power what I currently have plugged into it for around 3 hours. This
particular unit also supports Apcupsd very well, lots of useful info can be
obtained with the apcaccess utility which simply queries the UPS for whatever
stats it is able to return. Now granted I did get an extra battery for it that
is currently connected, the regular unit with the inbuilt battery by itself
might run things for closer to two hours (just an estimate). Another interesting
thing that I have noticed via running Apcaccess is while you may have all the
outlets taken at any given time, the power that all those devices draw
cumulatively does not equal a steady 120V at any given time. For example, if I
recall I currently have my server, USB hard drive, Ethernet switch, wireless
access point, and perhaps a couple of other things plugged in, and apcaccess
will still report current load as being around the 10-14% range. Good luck
finding a unit!
On Thu, Jun 13, 2013 at 06:43:56PM -0600, Scott D. Henning wrote:
> Hello Greg,
> 
> I use UPS on mountain top transmitter sites in radio broadcast and
> can offer some thoughts. As most respondents have pointed out, run
> time is probably not going to last 3 plus hours without massive
> batteries. Thus the software suggested to take the system down
> gracefully is good advice.
> I agree with your thinking thru how the server logic to restart when
> power is available might cause a "loop". Perhaps the software
> suggested in a recent reply can handle this, too. Systems fall
> victim to logic controlled protection easily as you suggest. I have
> trekked up a small mountain in winter to reset a consumer UPS when
> AC power failed, the batteries exhausted and the UPS was to dumb to
> realize AC was back...that was the last consumer unit we used..
> The model we most often use is the APC rackmount 1500'  something
> like RM1500 is the model. It has software, but I have not used it
> for Windows or Linux. It will restart when AC returns. It will not
> work on any but the perfect generator. That is one with very small
> variations in frequency. There are setup switches to allow wider
> swings in voltage to be passed thru without tripping the UPS. This
> is usually OK due to the switching supplies used in most modern IT
> equipment and sometimes works on generators that only vary in
> voltage.
> The solution for a generator that is not running with perfect AC
> output is not a line interactive model like the usual UPS (including
> the APC model I mentioned) but an online type of UPS. This is a
> charger driving batteries powering a constant DC to AC converter.
> The model I researched, but have not purchased is from Emerson
> Liebert. While the APC 1500 costs 800, the Emerson Liebert is more
> like 1100.
> I know the APC has a screen, but I think it will plug and play,
> except for the small switches in back to set voltage tolerance. The
> Emerson will need sighted help from what I can tell from the web
> site info.
> There is also a product from SurgeX that is not a UPS at all, but
> reads power quality and kills outputs when it is bad AC and begins a
> delay timer after the AC is considered good. This delays return to
> AC if it is likely to bounce several times after the initial event.
> Not cheap in the hundreds of dollars based on model and capacity. I
> do not know if it has communication via serial. I can not see the
> logic that might allow the server to shut down gracefully and not
> return until 'good' power returns. A wild thought is to have servers
> wake on LAN and let LAN switch die on loss of power company AC. The
> servers are on the UPS which signals loss of AC and the shut down
> occurs, then the system will not restart until LAN switch is
> functioning again. Just an idea.
> 
> HTH
> 
> Scott
> 
> 
> 
> -- 
> Scott D. Henning
> Architectural Audio Design
> PO Box 1372
> Durango, Colorado 81302
> 
> 
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-- 
Igor

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