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Does anyone know how to calculate UPS Power assuming I have server with 650 of watt.

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I asked a similar question on -… – Dan Aug 1 '09 at 15:41
up vote 8 down vote accepted

Math is nice and all, but if you'd rather pick and choose from a list of equipment you might consider using the very nice UPS sizing tool from APC:

I don't always purchase APC UPSs, but their selector tool can "do the math" for you and gives you some numbers in the end that can be applied to any UPS manufacturer's offerings (as well as, of course, some suggested APC products).

If you really want to know how much current your device is using I'd recommend using a clamp-on meter to test it. (You can certainly use something like a "Kill-a-watt" if you have it, too. The clamp on meters are nice because you don't have to disconnect anything.)

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Thanks for the info,especially for selector tool link – Funky81 Aug 1 '09 at 14:52
Have a link to the clip on meter? I have a kill-a-watt but have never seen a clip-on version... – Kyle Brandt Aug 1 '09 at 16:57
I'd want to double-check with an electrician friend, but I'm pretty sure you can't just use a clamp-on ammeter on a power cord because there are two conductors in the cord. You need to clamp it around just a single conductor to get an accurate measurement. – Ward Aug 1 '09 at 18:32
You are correct. You only use a clamp-on against one leg of the circuit, typically at the junction / breaker box. Clamping on against multiple conductors gives you something like the sum of the currents and, in AC, that should be nearly zero. – Evan Anderson Aug 2 '09 at 0:57
Evan is correct, its because AC is alternating so always switching back and forth. One leg cancels out the other. If its too much of a pain to get into a breaker panel or you want the load for a specific piece of equipment you can make what to need by making a cord and removing more outer sheathing so the 3 (still insulated) inside legs can be seperated and clamp-on can then be used. Of course you don't want to use this for long periods since its is unsafe by standards, but its fine for finding out the load. – SpaceManSpiff Aug 2 '09 at 7:02

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