UPS failure modes (was: fire at NAC)

Arman arman at
Thu May 29 21:33:28 UTC 2003

We are opening a new facility in SF and are seriously considering the idea
of by passing a large UPS (150-225KVA)altogether and relay on a generator
400-450KW with small UPSes on each rack.  A UPS failure would be limited to
a single rack, this way we could 

My personal experience with ATSes is limited and would appreciate any

Our new facility is dual feed from two different power grids and we could
provide two independant power feeds to each rack one backed via a generator
and the other std house power.  Customer are welcome to bring their own
UPS.  (we know it takes away rack space).

FYI;  Our experience has shown that all UPSes (we have used APC, Best,
Liebert and Minute Man) have all failed within a 5 year period.  We have
over 30 APC UPSes and a ~20% failure rate.


Joel Jaeggli wrote:
> On Thu, 29 May 2003, Bill Woodcock wrote:
> >
> >     > I had a little 2000VA rackmount Liebert UPS catch fire in 1997 and another
> >     > new and improved Liebert model almost catch fire about a year later.
> >     > What have others experienced as the failure mode(s) for their
> >     > UPS(s)?
> >
> > We had a two-hour grid power outage here in Berkeley yesterday, during
> > which time our APC Symmetra 16kva fried two of its four batteries, and
> > went into bypass mode, which meant that the transition back from generator
> > to grid caused everything to reboot.  :-/
> >
> > I've seen two previous APCs (both Matrixes) fry batteries...  The
> > batteries balloon up, and get really hot, and are too big to extract from
> > the chassis.  APC's solution to this is to have us take the entire UPS
> > offline for several days to completely dissipate the heat, and then try to
> > force the batteries out.  Since this seems to be an endemic problem, you'd
> > think they'd just design a chassis with somewhat more clearance around the
> > batteries so that failed ones could still be physically extracted.
> gell cells suffer from an electron mobility problem relative to
> traditional lead acid batteries. If you pull to much current off a stack
> of them you can boil the electrolyte off in a very big hurry, but because
> they're sealed they'll distent before they explode instead of just venting.
> I have run a matrix 5000xr with 4 battery enclosures down to zero
> under 65% load (220 minutes) without any untoward effects. in 100% load
> or overload conditions without forced air cooling (we lose ours in power
> outages) things could get uncomfortably warm.
> >                                 -Bill
> >
> >
> --
> --------------------------------------------------------------------------
> Joel Jaeggli          Academic User Services   joelja at
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