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HELP ! if my is power supply 1200 watts should i buy 1200 watts UPS ??

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January 12, 2014 8:36:43 AM

hey guys i need a UPS for my Workstation PC it has a 1200 watts power supply, i always use on a full load for 3d rendering in 2k resolution, i have a dual Cpu motherboard. I really need UPS for my PC , and for my professional works , so my question is, if i have 1200 watts power supply should i buy 1200 watts UPS ? or i can by any UPS ?? PLEASE ANSWER thanks !!!
a b ) Power supply
January 12, 2014 8:56:51 AM

Sorry, but it is more complicated than that.

If your power supply is an 80 Gold or Platinum for example, then that means that it will be taking at least 20% more that that from what it is plugged into (wall or ups) than the 1200 watts it will supply to the system.

In other words: 1200/0.8=1500 watt UPS.

But then all of that may be overkill. For example if your system is only drawing 400 watts total, then all you need may be 400/0.8=500 watt UPS, even if your PSU has the capacity to supply more. You will need to know exactly what your system draws in order to cut corners like this, and you could destroy the UPS and your system if you err.

The next thing you will need to consider for your UPS is for how many minutes you need it to supply your rated power for. That essentially equates to the size of the batteries in it.

http://www.apc.com/ has a wizard that can walk you through how to select an appropriately sized UPS for your system.
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a b ) Power supply
January 12, 2014 9:20:26 AM

Any UPS will do, it depends on how many minutes you want for back-up in power failure situation.

With 600VA UPS you will have around 5-10 mins of backup time.

And UPS doesn't depend on PSU or vice-versa, so you can have any.
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a c 271 ) Power supply
January 12, 2014 9:27:08 AM

Thats not quite correct lonewolf, if you exceed the maximum output capabilities of the UPS it will just shut off. If your UPS only has an inverter capable of handling 600W and you try to draw 900W from it, the inverter cannot magically grow in capacity to keep up with the load so the UPS will immediately shut off and its as though you didn't have a UPS in the first place. Watts and VA are a measure of instanteous power, Watt-hours are a measure of how long it will keep your system on for, these are very different numbers in a battery based system.


In general, you don't need a UPS the same size as your PSU, find out what is in your machine and you can accurately ballpark the power consumption and figure out how large of a UPS you need from that.
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a b ) Power supply
January 12, 2014 10:15:33 AM

lonewolf7 said:
Any UPS will do, it depends on how many minutes you want for back-up in power failure situation.

With 600VA UPS you will have around 5-10 mins of backup time.

And UPS doesn't depend on PSU or vice-versa, so you can have any.
With all the hardware the OP has, a 360W UPS will most likely shutdown if there's a power failure. The UPS has to be powerful enough for the maximum load and then the OP needs to determine how long it should run. Without knowing why the OP bought a 1200W PSU, I'd suggest a 1500VA UPS.
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a b ) Power supply
January 12, 2014 11:26:11 AM

To hunter315 and GhislainG, can I ask both of you a simple question ! If the OP doesn't use a UPS and plug the PC directly to the wall, 1. how many volts he will be getting from the wall ? It differs from country to country like (240V@60Hz, 220V@60Hz, 110V@50Hz) and so on.....

2. Will his PC run or not ? (without a UPS)
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a c 271 ) Power supply
January 12, 2014 11:37:25 AM

1. Any 1200W PSU is going to have Active PFC, it has to or it would be tripping breakers like no ones business, so the PSU doesn't care what voltage it gets from the wall. Not sure why you are asking what voltage it would get from the wall though, in general that doesn't make a significant difference, and as you said earlier it varies by region

2. Yeah of course it will run without a UPS because the only restriction on the power capacity of the wall outlet is the breaker down the line, a 15A breaker on a 110V line gives you access to 1650W of power.

I'll be honest, I'm not really sure what you are getting at here lonewolf
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a b ) Power supply
January 12, 2014 11:53:13 AM

So you gave the answer of your own question. So when you normally connect the PC to the wall, it delivers a power of 220V. So the output of the UPS also has to be the same to make the PC work. The 600VA is the maximum rating of power it can handle.

I dont think it would matter much. Only your backup time would go down or up, depending on what your PC's total power usage is. Don't look at your PSU, just calculate what your total power consumption is of the PC.

I found this item, and a discussion about the power factor which explains why there is no exact match between the two, that might be useful to anyone else who might have questions about this -- http://www.powerstream.com/VA-Watts.htm.

And here's another good one : http://www.generatorguide.net/watt-acpower.html
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a b ) Power supply
January 12, 2014 12:13:35 PM

I can't figure out what you're trying to say. 120V or 220V is voltage, not power. Power is expressed in watts (volts x amps = watts). You can't assume that a 600VA UPS means a 600W UPS; you have to check the manufacturer's specs. If a UPS can provide 360 watts, then it will trip if the load is exceeded to protect itself (just like a 15A breaker trips if the circuit draws 20A).

http://www.apc.com/resource/include/techspec_index.cfm?... provides 360W maximum. As you can see, the graph stops at 360 because it powers off when that load is exceeded.
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a c 271 ) Power supply
January 12, 2014 12:13:42 PM

Ahhhh i found the source of the confusion, once you start getting into power the units start getting confusing.

V and VA are not the same thing, VA(Volt-amps) is a unit of power with a slightly different definition from watts. Simple loads like toasters draw the same number of watts and volt-amps, more complicated loads like a motor with its big inductive coil will draw more volt-amps than watts, but active PFC makes computers look more like toasters so we will work off of watts for the sake of this discussion.

The UPS will output the same voltage as it takes in from the wall, lets say 100VAC(Volts-alternating current) for easier math, if the UPS has a 600VA capacity and a 600W capacity(easier discussion) then the computer can draw up to 6A from it, this will be a total draw of 100V*6A=600VA=600W.

Now if the UPS doesn't have a large inverter to it but is hooked to a massive battery bank it might have a 1200Wh(watt-hour) battery bank, this means that you can pull 200W for 6 hours, or 600W for 2 hours, or 1200W for 1 hour from that battery bank, but you can't pull 1200W from your 600W inverter down stream so if your load is trying to pull 1200W even though the battery bank could support that for an hour the inverter that converts it from DC-AC voltage cannot so the inverter will shut off to protect itself turning off power to the PC.

For UPS's because they are batteries feeding an inverter there are two primary stats, what is the maximum output of the inverter(Watts is the figure important for computers), and what is the hold up time for a specific load(this is determined by the size of the battery bank)
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a b ) Power supply
January 12, 2014 12:32:37 PM

A UPS is not 100% efficient. Presume 60% efficiency, a 600VA UPS provides 360W. In theory if an 85% 1200W PSU is loaded at 100%, it will draw 1200/85*100=1411W from the outlet; therefore the UPS would have to provide that much output power and, depending on its efficiency, it would draw 16-20A on a 120 volt circuit. In this case, an APC Smart-UPS 2000 would meet the requirements.

The OP has to determine his system's peak power draw instead of relying on the PSU specs and then select a UPS that will meet the requirements.
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a b ) Power supply
January 12, 2014 12:42:16 PM

Ok, this is not going anywhere, just a bunch of tech talk, to clear things up I just want to say, I have few high end PC's at my home, with big PSU's on them and every PC is attached to UPS ranging from 600VA to 850VA. And I am getting 5-10 mins backup time on power failure situation depending on PC specs and UPS specs.

So I am talking through my personal experience, that you can use a lower capacity UPS with a higher capacity PSU, it doesn't matter, the only thing that matters is the back-up time.

P.S. We don't know about the system specs of OP, it can be that OP's power consumption during max load never reaches beyond 600W, so a 1500VA UPS might be an overkill and waste of money.
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a b ) Power supply
January 12, 2014 1:10:47 PM

What's the actual power draw on your systems at peak, according to your UPS? You don't have issues because the UPS is not overloaded when a power failure occurs. That's why I said the OP has to know the peak power draw of his system, not the useless PSU specs.

I also have my systems on 2 UPS (1000VA and 1500VA) and even though my servers PSU specs exceed the Smart-UPS 1500VA specs, I'm not worried because the maximum power draw is less than 980W (approximately 600W which is good for at least 15 minutes). As the batteries get older, that time unfortunately decreases.
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a b ) Power supply
January 13, 2014 6:20:12 AM

Yes I agree with you " As the batteries get older, that time unfortunately decreases."

In most cases, average users do not need more than 600/700W, so a low power UPS can handle that easily.

I can say I use a i7 with 2 x 780Ti with 5 2TB HDD's with 2 ODD's with 2x 22" monitor and XFX 850 PSU and a 750VA APC UPS, and my wattage never exceeds 750W, so I never faced a problem with my UPS, where as the maximum wattage for UPS is 500W. But I couldn't get more than 5 mins backup time.

Here is a link of my UPS : http://www.apc.com/resource/include/techspec_index.cfm?...



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a b ) Power supply
January 13, 2014 7:20:56 AM

You're fine because, unlike the OP, you probably never run your system at max load while a power failure occurs. Even while gaming your system doesn't exceed 500W. As a test, run benchmarks to load the CPU and GPUs at 100% and then pull the plug on your UPS. If your total system power draw exceeds 500W, the UPS will most likely shutdown. Please note that the GPUs alone should draw 520W.
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a b ) Power supply
January 13, 2014 7:57:49 AM

Yeah nobody uses their PC's on full load during power failure, so no question about gaming during power failure. We all are in a hurry to properly shutdown the PC, and it takes max 2 mins to do it. Cheers.

BTW where is the OP ? We are arguing for nothing for about 24 hours now and no sign of OP, LOL. Have a good day.
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a b ) Power supply
January 13, 2014 8:29:46 AM

He's having fun reading this thread!
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February 21, 2014 1:41:39 PM

dafuqawew said:
hey guys i need a UPS for my Workstation PC it has a 1200 watts power supply, i always use on a full load for 3d rendering in 2k resolution, i have a dual Cpu motherboard. I really need UPS for my PC , and for my professional works , so my question is, if i have 1200 watts power supply should i buy 1200 watts UPS ? or i can by any UPS ?? PLEASE ANSWER thanks !!!


I would buy at least a 1500watt UPS battery backup to cover a 1200watt power supply from hard experience. Read you need 20% more than the PSU is rated.

I have a 1200watt Pc Power & Cooling PSU with a small fraction of the wattage ever in use now. I have one Graphics Card now, used to have THREE power hogs in Crossfire.
The large 1200watt ULTRA UPS battery backup I bought as an upgrade to handle my PSU ALWAYS clicks all the power right off instantly claiming OVERLOAD whenever the power goes out! Found out way too late as I never pulled the plug to test it when bought. I stripped the outputs to ONLY the PSU with NO MONITOR even and still turns off instantly. And do not buy one that just says 1500VA or something ...must handle 1500watts. The companies do not make it clear at all. These are hard to find and VERY EXPENSIVE for a casual gamer and cost a fortune to ship.
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a b ) Power supply
February 21, 2014 1:55:23 PM

What model number is your Ultra UPS? If the UPS powers down when the PC is idle, then it's defective. If it's the PC that powers off, then it's because your UPS doesn't provide a pure sine wave output, not because it isn't powerful enough.
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February 21, 2014 2:16:41 PM

GhislainG said:
What model number is your Ultra UPS? If the UPS powers down when the PC is idle, then it's defective. If it's the PC that powers off, then it's because your UPS doesn't provide a pure sine wave output, not because it isn't powerful enough.


It is Model#RCD-UPS2000D It is a 2000VA model.

Says also on rear label: Input: 12a Max Battery Backup Output: 10.9a 1200 watts Max

The UPS does not power down when Idle. The UPS just goes instantly OFF with no power down, when the plug to it is pulled or power outage happens.

I did the Self Test by pressing the power button once and it went on battery for a second showing only one bar left at bottom...tried it again a few seconds later and the whole thing turned all power off again.
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a b ) Power supply
February 21, 2014 3:19:19 PM

Your batteries are defective or the UPS is not charging them completely. Fortunately they are inexpensive, but I presume there are 2 batteries since they only are 7A or 8A each?

2000 VA = 1200 Watts as most UPS have a 60% efficiency.
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February 22, 2014 1:45:56 PM

GhislainG said:
Your batteries are defective or the UPS is not charging them completely. Fortunately they are inexpensive, but I presume there are 2 batteries since they only are 7A or 8A each?

2000 VA = 1200 Watts as most UPS have a 60% efficiency.


The OVERLOAD PROTECTION Spec says: "If load exceeds 110% of nominal for 60 seconds, 130% for 3 seconds UPS shuts down automatically." In that I only get one second on battery before breaker shutOFF it is probably OVER 130% draw. These PC POWER & COOLING PSUs were famous for supplying the steady FULL amount of power as advertised at room temp unlike many others claiming high wattage but only delivered at odd temps etc. So I do not know if the 10.9a UPS output to the PSU is enough and it might be drawing a FULL 12a and blowing the breaker. The green bars are all there. They are maybe 4-5 yrs old now but failed me a few years ago the same way when they should have been ok. I would hate to throw good money after bad, but I do know the batteries do not last forever. I am wondering if I pull them whether I could order UPGRADED Higher amperage batteries in the same size like I did for my kid's electric toy riding car. Twice the energy and runtime I think it was.
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Best solution

a b ) Power supply
February 22, 2014 2:21:27 PM

You have to understand that a 1200W PSU draws only as much as required. If your system requires 200W at idle and your PSU is 80% efficient, then it will draw (200/80 * 100) which is 250W. If your batteries are 4-5 years old, then I'd be surprised if the UPS passes the battery test. Instead of conecting your system, connect something else like a 100W light bulb and see if the UPS stays powered up for at least an hour. I have a Smart-UPS 1000 and a Smart-UPS 1500 and they can run for at least 1/2 hour when my systems are idle (except the 1500 that shutdown within a couple seconds when there was a power outage and the batteries were at least 3-4 years old, but that's normal). You can buy 8A batteries, but you probably won't find 14A batteries at that size and characteristics; even if you did, I certainly wouldn't recommend that you do since the UPS wasn't designed for those.
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February 22, 2014 4:05:02 PM

GhislainG said:
You have to understand that a 1200W PSU draws only as much as required. If your system requires 200W at idle and your PSU is 80% efficient, then it will draw (200/80 * 100) which is 250W. If your batteries are 4-5 years old, then I'd be surprised if the UPS passes the battery test. Instead of conecting your system, connect something else like a 100W light bulb and see if the UPS stays powered up for at least an hour. I have a Smart-UPS 1000 and a Smart-UPS 1500 and they can run for at least 1/2 hour when my systems are idle (except the 1500 that shutdown within a couple seconds when there was a power outage and the batteries were at least 3-4 years old, but that's normal). You can buy 8A batteries, but you probably won't find 14A batteries at that size and characteristics; even if you did, I certainly wouldn't recommend that you do since the UPS wasn't designed for those.



Ok Thank you. That solved it for me I think. I pulled the UPS and ran a 75 watt bulb on it and it only survived 5 minutes on that bulb! I checked the web and saw 2-3 yrs is normal replacement time, so the batteries are shot. I will order new ones.
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a b ) Power supply
February 22, 2014 6:29:46 PM

It should run for at least 75 minutes on a 75 Watt load.
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