UPS Sizing

[Joseph Sinclair]

AC doesn't work quite as simply as VoltsXAmperes=Watts, because AC is constantly changing in amplitude, we have to apply some averaging equations to get the actual watt load (usually, this is the simple RMS equation, but it's much more complex when there are multiple phases, or the load is non-linear).
 That's why UPS units are sold by VA, not Watt.  As long as the VA rating is greater than VoltsXAmperes you should be just fine for household AC.  To determine runtime on battery, you should use the manufacturer's "typical" load (in watts) for the computer, and compare against the UPS manufacturer's chart.

==Joseph++

P.S. your manufacturer specs suggest that the *maximum* load for your G5 would be 125X7.5=938 VA, typical load is probably around 800VA at 115V.  A 1200VA unit should easily accommodate the computer, provided nothing else is connected that exceeds 250VA additional load.

Craig White wrote:
> Trying to figure out UPS size for a G5 (not that it matters).
> 
> According to Apple's Specifications on a G5
> 
> Maximum current: 6.5A (low-voltage range) or 7.5A (high-voltage range)
> for 100-125V AC, 3.5A for 200-240V AC
> 
> A Belkin F6C1200-UNV 
> <http://catalog.belkin.com/IWCatProductPage.process?
> Merchant_Id=&Section_Id=76&pcount=&Product_Id=199025>
> 
> 1200 VA unit has stated capacity of 670 watts.
> 
> Now my simple math says 7.5A x 115V is 862.5W which would suggest that
> this system is not sufficient for a G5
> 
> Is this correct?
> 
> I would need something at least 1500VA?
> 
> Craig
> 
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