UPS failure modes (was: fire at NAC)

Robert Boyle robert at
Thu May 29 16:31:42 UTC 2003

At 12:27 AM 5/29/2003 -0400, you wrote:
>Sheesh. Heh.
>We're still here.
>Part of a rectifier in a Liebert UPS let loose, causing a momentary fire.
>That is, until the FM200 quenched it.
>Since there seems to be interest, I will post the post-mortem to the list.

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. Both 
were operating well within specified input, load, and temperature 
parameters.  I haven't really trusted them since.I bought dual MGE UPSes 
for our datacenter in 2002. I figured if E****s can flip them on and off 
randomly and massively overload them all in an environment which is 95 
degrees F, then they should hold up nicely for us when lightly loaded at 65 
degrees F. :)

The reason for this rambling post is to ask if others have had similar 
problems with other UPS brands. I think they should have enough fail-safes 
built-in that they are never the CAUSE of an outage much less a fire! Based 
on my experience and NAC's incident today, is that an unreasonable 
expectation? I don't think manufacturers specify MTBF (mean time before 
fire) figures for UPS units. What have others experienced as the failure 
mode(s) for their UPS(s)? The static transfer switch should drop the load 
onto line/bypass power immediately and shut down the inverter while 
tripping the battery disconnect at the first sign of trouble - does this 
work as designed and advertised most of the time or just some of the time? 
Of those with UPS failure histories, what has happened in your situation?


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