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I am thinking about purchasing an APC that has a max power capacity of 2850 watts / 3000 volts. I only plan on plugging about 1000 watts of actual power into the unit however.

I'll be running this for a few home servers. Considering a standard US circuit is generally 15a, it seems that there is no way it could handle 2850 watts. A 15a circuit is generally designed for a max of 1800 and it should really only be around 1500.

My question is, if i'm only using 1000w hooked up to the APC, do I still need a run the unit on a circuit designed to handle 3000 or will the unit only need as much wattage as its protecting/ battery backing?

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closed as off topic by Sven, Zoredache, mgorven, growse, Falcon Momot May 17 '13 at 20:33

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UPCUPSAPC ≠ APS ≠ ABC –  ewwhite May 17 '13 at 19:45

3 Answers 3

up vote 3 down vote accepted

No, you will not pull 3000 watts of energy when you only have 1000 watts of equipment. The UPS has a maximum capacity of 3000 watts - that doesn't mean it sits there pulling 3000 watts of energy all the time.

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Thats what I figured, but is it safe to use on a standard socket like that? Here is the actual unit: apc.com/products/resource/include/… –  ryandlf May 17 '13 at 17:56
    
Yes it'll work fine. Though if you don't have a need to support 2800 watts of equipment, and you don't have a mains circuit strong enough to support that even if you did... you might consider buying a smaller UPS. –  Ryan Ries May 17 '13 at 17:59
    
Its a great deal I found online from a small business that is upgrading so I admit its more than I will probably ever need, but I figure if it lasts me a while I wouldn't have to get a new one. Otherwise i'd definitely be looking at something smaller. –  ryandlf May 17 '13 at 18:02
    
Better to have a bigger UPS than you need. Your battery run time will [most likely] be be better with this 3000VA UPS than a smaller UPS when loaded @ 1000W (assuming extended batteries are not involved). Just keep in mind that when the load meter on the UPS reads 50% you're probably approaching the point at which your circuit will trip. It's tempting to think you can add more equipment. If your 15A receptacle is on a shared circuit with lighting, other receptacles, etc, you probably don't want to get anywhere near the 15A / 1850W max. –  s.co.tt May 17 '13 at 18:11
    
Also: The UPS will draw more current when charging after a power outage (not a trickle charge, but a full charge). APC doesn't publish that information for some reason, but I was able to find a post on the APC forums where a similar 3000VA UPS can consume an additional 287W (~2.39A, assuming a PF of 1.0) when charging. You should factor that in when planning your load. –  s.co.tt May 17 '13 at 18:26

When the UPS is fully charged it only draws slightly more then the load of the attached equipment.

When it needs to re-charge it draws the load of the attached equipment + the charging current.
Better check what the max charging current is.

Chances are VERY HIGH you will overload those 15 AMPs.

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If your wiring is rated to handle at leat 15 Amps then the worst that will happen is the circuit breaker will trip if the UPS load exceeds 15 Amps.

If your wiring is not rated to handle at leat 15 amps then you risk having an electrical fire if the UPS load exceeds the rating of the wiring (if the load exceeds the wiring rating but doesn't exceed the circuit breaker rating).

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Good call on the wiring as well as the circuit. –  ryandlf May 17 '13 at 18:21

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