UPS backup musings

[Scott D. Henning]

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