Our old network admin bought the top range UPS a few months ago but never came around to setting it up and is no longer with the company. Now the old UPS broke down and needs to be replaced, but an external company that did an audit said that that UPS won't work.

Now we are no hardware specialists, but the difference in specs is a higher output from 5A to 8.8A meaning a higher output. But isn't the UPS supposed to give the server the required output anyway?

This 'independent' audit does sell its own hardware including UPSes so I'm not sure how much bias they have. Is there a reason why we can't replace the old broken UPS with the new more powerful one? Is there a way we can check to see if the UPS works with our server?

ok, i wrote down the numbers again, the Volts and Amps are what are on the back (where you connect up the plugs which seem diffrent from on the front label.)

old one

APC SmartUPS 1500 220-240V -- 6.8A

new one

Dell UPS 1920W 250V -- 10A

  • note that watts = amps x volts. Most computer power supplies (in the US) will be 120v, so best case without considering efficiency, the 8.5A is going to put out approx. 1000watts. This would be the maximum wattage based upon equipment you can plug into the UPS (such as 20 50watt light bulbs)
    – horatio
    Apr 4, 2012 at 14:00
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    -1, this belongs to skeptics.stackexchange.com. [/irony] Seriously, I thought this would be some conspiracy against UPS
    – fjdumont
    Apr 4, 2012 at 15:00
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    Ask them why it won't work. It's just possible they spotted something that's not immediately obvious from the info we have.
    – BJ292
    Apr 4, 2012 at 15:25
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    Great analogy: Electronic devices all have resistance. You can't force more current through, it draws a finite amount (based on the voltage divided by resistance). Raise the resistance, lower the current. Raise the voltage, raise the current. (and no, the resistance is not always constant) Apr 5, 2012 at 0:09
  • I'm not certain about this, but wouldn't the new one blow your fuses on a full load if you have 7-9A fuses? On the other hand, 6A to 10A is the standard gap in my country, so I don't know if such fuses exist.
    – onik
    Apr 5, 2012 at 9:18

10 Answers 10


There is no reason the UPS will not work if the input voltage is correct to your country and the output is the correct voltage. The UPS will provide the needed current for the attached devices.

Be sure you have the correct outlets as some higher output units may use a different plug than others. Some may have a standard 15A outlet while others a 20 or 30A (often a twist lock)

Based on your update the Dell should work fine. If you need additional info, a call to the local Dell office or their online Chat will help you as well.


Post the model number for a specific answer. The only problems I can forsee is that the output voltage could be incorrect as mentioned by Dave M., the input circuit might not support enough amperage as mentioned by soandos, or the actual input plug might be of a standard for which you don't have a socket.

Some high-end datacenter UPS units output 208v instead of the standard US mains voltage of 120. If this is the case you can't run your normal equipment on it unless it's designed for 208v. Also the input amperage is specified in the manual. It might require a 20, or 30 amp circuit from the breaker box which may not be what you have in the wall.

Also as mentioned - the twist lock type of plug (probably a NEMA L5-20 or 30) requires a special outlet. Good luck!

  • 1
    i added the model number. we are in europe, so all outputs are the same 240V (the new one says 250V, the old one says 220V-240V actually) all sockets are the normal ones you find in normal pcs and screen, no twisties.
    – Andy
    Apr 4, 2012 at 14:33
  • I'm running a 120v 1920w in one of my data closets. Is yours a tower or rack-mount configuration? I can't find any reference to a 250v model though, only 120, 208, and 230. I'd find the specific manual either included or on the web and check input and output specs. I think you're probably ok though.
    – Josh
    Apr 4, 2012 at 14:48
  • its a box. the labels on top of it state its a 240V one (thats what we have normally on the net) but the back stated 250V out.
    – Andy
    Apr 4, 2012 at 15:01
  • 250V is simply the maximum voltage. Anyone that says it cannot be used is telling you a bold face lie. Your old UPS could handle less power consuming devices, being able to support more devices, can only be a good thing. This isn't to say the UPS itself is good quality, dell is not exactly a high-end brand, APC is well known in the UPS industry.
    – Ramhound
    Apr 9, 2012 at 14:17

UPS current specification represents the maximum current the UPS can give, and is directly proportional to its rated power, if voltage is constant.

If your connected equipment's total power (or current) exceeds this value, your UPS device's protection will trip, or you will damage it. That's why it's always better to take a device with higher nominal power.

However, if you are comparing two completely different models, of a different price range, things may be slightly more complicated with newer server power supplies. For example, 6th generation of HP Proliant servers completely refuse to operate with lower end UPSs, because their voltage waveforms (when operating on battery) produce too much THD. For these servers, a higher end online UPS or double-conversion is needed to continue running during blackouts.

That's why it's important to know exact models of both UPSs. If new UPS is the same model as the previous one, but with a higher rating, then it should only behave better with the same load.


I am pretty sure that there is nothing to worry about, and the UPS will be fine.

If however, you are worried that it will short, or overload, or whatever, just plug the UPS into the same surge protector or similar device that you use to regulate power flows now (it is not like wall current is that steady anyway). Worst case, it trips the breaker, and you know you need a new one. Best case, it just works.


A UPS can be largely overrated; it is better to be at least some overrated, than underrated. One that is too far overrated, could be less efficient, but can still run with less wattage draw for a longer time.

Are they trying to sell you something? Yes, they probably are. But the power rating on a UPS alone does not determine the quality of the UPS. When they made the claim that it "would not work", what was the claim based on?

  • the took a look at the UPS, one at the server, and said, this won't work. they didn't say this to me and apparently, they didn't say anything more then, it won't work. seems strange since its more powerfull then the current one and the most powerfull one of its line.
    – Andy
    Apr 4, 2012 at 14:36
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    @Andy I have had non-computer contractors do the same thing. 3 hours of extensive research later by myself, and more facts under my belt, we told them how they will apply what we had :-) They whine a bit about code, or make other claims, and we just show them the paperwork, or the code, or the stats or the facts. If they make another claim i have no facts for, it is back to more research. (then we never hire them again :-)
    – Psycogeek
    Apr 4, 2012 at 14:43

This might be a stupid concern, but I see nobody pointing that out: what about the overall quality of the new UPS?

Is it a noname, made in china, untraceable company? Does it look like poor build or refurbished?

For the rest, except for the output voltage (if it outputs 240V, double check your server can accept this (they usually do)), you should be fine.

And also blacklist the company that tries to force sell their UPSes

  • the new one is a dell one, the same brand as the one our audit was partnered with.
    – Andy
    Apr 4, 2012 at 14:34

As everyone pointed out... based on the info you provided, the larger one will work.

That said, UPS also (sometimes) supplies signals to a server that power has been lost so that a monitoring program on the server can either alter an admin, or begin to shut down the server gracefully. If the larger UPS lacks these (or other) features, it might be fine for using to provide power, but might not fit into the entire power management solution in place.

Just something to keep in mind that UPS's have more functions than just the battery :-)


Haven't seen this exact answer yet, but could it be that your input supply is not beefy enough to supply the UPS's maximum power drain?

I see that you are in Europe and on 220 VAC. But in North America, the standard circuit and outlet is 120 VAC, rated 15 amps. Multiply those together, and you see that the standard outlet can only supply 1,800 watts, and yet the Dell is rated 1,920 watts.

So if this were in North America and it were to be plugged into a standard outlet, it would not be legally "to code," so to speak, because you should never plug something into a circuit that is capable of overloading that circuit (except during a fault). You would need a special 20 amp outlet and plug. In North America, such an outlet has one blade rotated 90 degrees, so it is physically incompatible with 15 amp sockets.

That said, my guess is that if the physical plug is the same, then it should work.

  • Given that this UPS's ratings are all spec'd at 240V I would say that the limitations of a NEMA 120V 15A outlet are irrelevant. Nor are 20A outlets all that uncommon in NEMA installations. Oct 20, 2015 at 21:09

I can't be sure from the information provided, but I think it's possible that those power ratings you've posted are for the input side of the UPS. Find out what the output side is. It's possible that the old UPS puts out 120V, and the new one is 240V. If that's true, then you'd either need to make sure that all of the devices plugged into the new UPS can take 240V input, or you'd need to use a PDU, a voltage-converting power distribution unit, to do the voltage conversion for you. But check your devices -- many if not most servers and network devices sold today are either universal-voltage power supplies, or they have a switch to select 120 or 240V.

Note also that, if you are using 240V on your new UPS output, then all of the plug strips and outlets downstream of that UPS need to be either 240V outlets, labeled as such, or both. This gets into safety and electrical code issues as well, so it's in everyone's best interest to get this right.


UPS-es do not break. Usually you can replace broken battery cells and extend UPS lifetime infinitely. If you buy UPS too strong (like 50A to feed 2A computer) batteries do not excersise enough and might wear off faster.

  • Sure..They can break if they are hit by lighting or some other surge causes them to trip their breaker, most of the time, its a one use breaker. You might be able to replace said breaker, often times, its easier to just replace the entire unit
    – Ramhound
    Apr 9, 2012 at 14:22
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    I've had a couple of UPSs break, and it wasn't the battery or the breaker. The inverter (the part that takes DC from the battery and makes AC) failed. Oct 20, 2015 at 21:00

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