[c-nsp] pop site battery backup recommendations

[Seth Mattinen]

On 7/22/2010 08:45, Mike wrote:
> 
>    a) went berserk and flooded the network with garbage
>    b) issued spurious "turn off ups" commands to the ups
>    c) began automated self test cycles that shut off the ups (even when
> self-test is disabled!)
>  
>    I further have experienced UPSs that for whatever reason, did not
> switchover during an outage, or did not provide sufficient filtering and
> allowing connected (and supposedly protected) devices to get zapped and
> either fry outright or lockup, or vary in their output voltage too much
> during a failure causing lockups/outages due to 'over voltage'. They've
> also failed to restart once AC power came back on, requiring staff to
> drive out and press a button.  I've also had units that religiously run
> their self-tests but then fail during an actual ac power outage. In
> short, I have seen it all.

I've seen most of that as well, the most infuriating being C in your
list. I have also seen the relays in the line interactive models fuse to
one side or the other and you'll never know about that one until the
power fails.

Your filtering and no-switchover issues would be solved by using an
online (also known as double online) UPS. Because it always runs the
power through the ac-dc-ac process you can be absolutely certain it's
working because it's already doing it the whole time. Plus since it's
regenerating AC itself the output is not affected by (or even connected
to) the input. Online units have a battery test mode, but they don't do
a "self test" like a line interactive unit would do.


>    To their credit, I have experienced many many cases of ac power
> failure that these units did gaurd against and provide enough runtime
> for either local power company repair response or for our own internal
> response to come install a generator. But the continuing saga of the
> UPSs themselves causing outages, is really beginning to wear on me and I
> am looking for a better and more intelligent solution.
> 
>     I think what I need, is an online ups solution as opposed to the
> APC's we have been deploying. My wants are reliable operation, 1000 -
> 1500va, expandable battery capacity, simple remote network monitoring,
> and reasonable cost of course (;-). My team is frustrated and is
> threating to design and manufacture our own brand of UPS's if the market
> doesn't have anything that gets it right, but surely there's got to be
> something out there folks can trust and I want to know what it is.
> 
> Thanks for your suggestions in advance.
> 

Yes, you would be much better served by an online UPS, which would be
anything in the Smart-UPS RT series if you want to stick with APC. Below
that it's just line interactive. An online UPS also has a bypass in
them, so in theory any faults should cause the unit to switch to bypass
and send an alarm rather than dumping the load. I'll stress the "in
theory" part because it's still a relay in the RT series, not a static
bypass, and the UPS can't monitor the health of a relay. Units with a
static bypass can monitor the health of the SCR that makes up the bypass.

The cost for an online UPS will always be higher than line interactive,
but well worth it to eliminate many of the problems you described.

~Seth