"They all suck!" Re: UPS failure modes (was: fire at NAC)

Thu May 29 20:29:53 UTC 2003

Or we could all take a page from the book of telecom, and run with DC systems.

No inverters involved, lots of parallel rectifiers and battery power just
sitting there.

If only the equipment manufacturers would stop gauging on price for
DC equipment/power supplies.

Dan.

Alex Rubenstein wrote:

> > UPSes (and UPS batteries) do fail, sometimes in catastrophic ways.  I
> > would not design any critical system on the assumption that any particular
> > component won't fail.  High availability is about designing for failure.
> > Sometimes there is a long time between failures, other times they occur
> > early and often.  The most annoying thing about UPSes is they fail at
> > exactly the time they are needed most.
>
> Except, that:
>
> Even in instances where 'High availability' is designed, in the case where
> one of the units has a failure that causes a fire and FM200 dump, either
> the FM200 will still trigger an EPO, or the fire department will.
>
> So, the second 'high available' unit will generally not prevent you from
> dropping the critical load, but instead, will help you get back on line
> quicker.
>
> A much cheaper and easier to implement external maintenance
> make-before-break bypass will accomplish the same thing.
>
> I've heard many a story of the paralleling gear causing the problem in the
> first place, as well...
>
> -- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
> --    Net Access Corporation, 800-NET-ME-36, http://www.nac.net   --