On Mon, 05 Feb 2007 02:26:26 GMT,
wrote:

I have to admitt that I am assuming the cause of the failure is
current inrush. The PSU is an Antec Phantom 500 watt, so I guess that
wattage would be the normal sustained load for which it is designed. I
believe my earlier comment regarding normal computer internal (CPU,
hard drives etc) wattage is high.

The UPS units are APC Back-UPS XS-1000 and XS-1200 models which I
believe are rated in-excess of the 500 watts of the PSU.



The PSU wattage does have an indirect correlation to the
inrush current "possible" (depending on existence of and
spec of component(s) used to provide the current limiting),
but does not directly determine the peak possible. That
peak is merely a result of what an unrestricted current flow
into the electrolytic capacitors would cause.

In other words, it doesn't matter at all how much current
the computer itself uses in this case, the problem could
occur even if there wasn't any computer connected to the UPS
at the time (it was turned *on* by the AC input switch).