David Magda wrote:
On Jun 30, 2009, at 14:08, Bob Friesenhahn wrote:
I have seen UPSs help quite a lot for short glitches lasting seconds,
or a minute. Otherwise the outage is usually longer than the UPSs
can stay up since the problem required human attention.
A standby generator is needed for any long outages.
Can't remember where I read the claim, but supposedly if power isn't
restored within about ten minutes, then it will probably be out for a
few hours. If this 'statistic' is true, it would mean that your UPS
should last (say) fifteen minutes, and after that you really need a
generator.
Most UPS's from any vendor are designed to run for around ~12 minutes at
full load. So that would appear to back
that claim up and from my experience that is pretty much on the money...
At $WORK we currently have about thirty minutes worth of juice at full
load, but as time drags on and we start shutting down less essential
stuff we can increase that. The PBX and security system have their own
UPSes in their own racks, so there are two layers of battery there.
The problem comes when the power cut comes and you aren't there in the
middle of the night. Then you either
need an automated shutdown system instigated by traps from the UPS
(shutting things down in the correct order)
or a generator. About here the generator becomes a very good option. The
above no generator scenario needs to be consistently tested to maintain
it's validity, which is a royal pain in the neck. Gen sets are worth
their weight in gold. I can't
even think how many times in the last few years they have saved our
bacon. (through both planned and unplanned
outages)
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