[tech] [committee] Auction TOMORROW for UPS

[Duncan Sargeant]

2011/3/9 Daniel Axtens <danielax at gmail.com>

> > For the UPS' sake, running only for 90 seconds doesn't take the battery
> > anywhere near to the UPS' "discharged battery" threshold which, for these
> > small SLA batteries, kills them without too many cycles to flat. I
> suspect the
> > UPS manufactures underrate the battery and are relying on the idea that
> most
> > power losses are short.
>
> This is one of the best thought-out responses I've received to anything
> this year. Thanks Harry.
>
> I've also been told on IRC that we do have machines dying due to power
> issues, and that, to [BOB] at least, not having to rebuild his screen
> session is worth $1000.
>

What are you guys trying to achieve?  Power conditioning, 2 min uptime, 30
min uptime, or longer?

A well-maintained UPS can be expensive to run.  The equation is something
like: purchase cost + electrical install + 2-yearly battery replace/dispose
+ service costs.

OK, so you can skimp on the last two, but - and I'm hazy on this - dying
lead acid batteries will just suck charge continually while not actually
charging.  But if it is a (more expensive) double conversion UPS (AC-DC-AC),
it will make a nice, but warm, power conditioner.

I'd get a quote for the extra circuit, because it may not be trivial if they
don't have capacity upstream.

My experience with UPSs is that sometimes it is better to have multiple
small ones than one big one.  They are more disposable, and operating on
common 10A circuits makes the electrics much cheaper (you can also get
yourself into trouble with overloading easier, I guess).  Liebert is a good
brand but even their service guys warned me that like everyone, they make
crappy consumer models too.  One thing I would stay away from are modular
UPSs.  APC and Liebert make them where you can hotswap PSUs in and out - the
general wisdom is that the hardwired ones are more reliable (hotswap
batteries are fine).

I just specced and installed them for a while, hopefully this post will
attract comments from others more clued into electricals :)

,dunc
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