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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Sat Aug 27, 2005 10:20 pm Post subject: UPS Systems |
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Does anyone know how to work out the time a UPS will last if you only know the VoltAmps (VA) of the UPS and the load you are going to put on it in Watts?
(BTW, 1VA = 1Watt, thanks google!)
I have seen several different 600VA UPS systems that all claim different times, one said 45 mins, the other said 24 mins and another said 6.4 mins.
If anyone knows the answer to this or has a formula please, please, please post. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
www.abyssunderground.co.uk |
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k1ll3rdr4g0n -
Joined: 04 Jul 2004 Posts: 609
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Posted: Sat Aug 27, 2005 10:31 pm Post subject: Re: UPS Systems |
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The Inquisitor wrote: | Does anyone know how to work out the time a UPS will last if you only know the VoltAmps (VA) of the UPS and the load you are going to put on it in Watts?
(BTW, 1VA = 1Watt, thanks google!)
I have seen several different 600VA UPS systems that all claim different times, one said 45 mins, the other said 24 mins and another said 6.4 mins.
If anyone knows the answer to this or has a formula please, please, please post. |
It all depends on what is on the UPS when the power goes out.
A computer sucks apx 300watts, or whatever your power supply says it uses.
(Thats without a monitor).
A computer would probably last about 30-40 min on that UPS.
(Just my guess). _________________
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Sat Aug 27, 2005 10:36 pm Post subject: |
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Hmmm, 30 mins was what I thought but I would have thought there would be a forumula of some sort to work out how long a 600VA UPS having 300 watts taken out of it would last.
I would assume from that, that at 25% load it will last 1 hour and 50% load 30 mins, etc. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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MonkeyNation -
Joined: 05 Feb 2005 Posts: 921 Location: Cardiff
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Posted: Sat Aug 27, 2005 10:46 pm Post subject: |
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How long would a 550watt PSU last?
15 minutes? _________________
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Sat Aug 27, 2005 11:13 pm Post subject: |
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Well it seems that way but I still havent got a formula to work it out. None of the ones I look at tell you the time it will last on a full load. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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richardyork -
Joined: 22 Jun 2004 Posts: 410 Location: United Kingdom
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Arctic -
Joined: 24 Sep 2004 Posts: 560
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Posted: Sun Aug 28, 2005 8:55 am Post subject: |
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You need to know how much power it sucks per second...
Personally, I'd look into something that automatically restarts a computer. A UPS is practically a uselessly costly expense, and I would have wanted a thing that automatically restarts my computer over anything on my trip. |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Sun Aug 28, 2005 10:04 am Post subject: |
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Hmm, these are a bit out of my price range but there were some on www.ebuyer.com that are in my price range. I was taking a look at them. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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Anonymoose -
Joined: 09 Sep 2003 Posts: 2192
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Posted: Thu Sep 01, 2005 12:41 pm Post subject: |
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The Ebuyer stuff is cheap and cheerful, but should do the job for a home server. Knowing that stuff isn't going to blow up on a whim during a storm, or randomly die without flushing buffers to disks etc adds to your peace of mind :)
However, what you need to understand is that it isn't as simple as saying "I have a 300W PSU, how long will this last?" - the wattage of the PSU is the maximum it can draw under load. It should draw considerably less while actually the PC is running in normal operation depending on what components you have in your PC - number of HDs/CD/DVD, processor spec, graphics card spec etc. A PC with a 550W PSU could last longer than a 300W PSU connected to identical UPS's - if the 550W PSU PC contained components with a total power draw lower than the 300W PSU PC.
I keep my PC hooked up to an energy monitor which shows the actual current power draw in watts.
The PC is a 3.06GHz P4, overclocked to 3.2, a Geforce 6800GT, 1GB of DDR, 2 HD's and a DVD writer. At the moment, under basic use (ie me writing this, browser other sites, and listening to a MP3s) it's currently drawing 110-115W of power. If I force the processor to full load, for example running a benchmarking session of John the Ripper, that rises to 180W. You then need to go from the wattage back to the VA - roughly W/0.7 = VA, so in my case, around 257VA at full load.
The UPS backup times you find should be stated at full load - so for example, a 1000VA UPS running at full load could be expected to last 10 minutes. If you are drawing less than this, the run time would extend proportionally.
Taking my system as an example, the UPS is an old APC SU1000INET which I picked up 2nd hand... Specs here :
http://www.apcc.com/resource/include/techspec_index.cfm?base_sku=SU1000INET
Handily, they quote loads in W rather than VA so there's less mucking about.
20.6 minutes (335 Watts) @ half load
You can roughly double that figure, since my PC is drawing less than half of 335 watts - so about 40 minutes of runtime.
The APC website has a handy UPS requirements calculator, but since they're obviously going to want to sell you a bigger, more expensive UPS, I'd take the results with a pinch of salt. _________________
"Invent an idiot proof webserver and they'll invent a better idiot..." |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 01, 2005 1:03 pm Post subject: |
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Thanks for that, your explaination is a lot better than any other I have read. My server will probably take even less because its a slower processor, and 1hd of 2 normally running all the time. The cd drives are rarely used.
Ill take a note of what you said and see if i can work out how much im using. I may even get a watt meter as you have.
Thanks again. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
www.abyssunderground.co.uk |
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Anonymoose -
Joined: 09 Sep 2003 Posts: 2192
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Posted: Thu Sep 01, 2005 1:09 pm Post subject: |
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I'd recommend the watt meter route if you want a real rather than hypothetical figure - they're on special at Maplins at the moment, and will probably be the most useful £10 you ever spend...
http://www.maplin.co.uk/module.aspx?ModuleNo=38343&doy=1m9
It will also show power usage in kWH - the units used on your electricity bill. Excellent to know how much you're actually spending on an average day running your PC, and once you've finished monitoring your PC you can whizz round the house and save yourself a bit of money working out what you should turn off more often :D _________________
"Invent an idiot proof webserver and they'll invent a better idiot..." |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 01, 2005 1:12 pm Post subject: |
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Yeah I never thought of that. A friend of mine was going to get one but forgot to pick one up last time he went.
Ill have a look at it and decide if i'm going to get one or not.
I worked out my PC at about 120W so thats 171.4VA, so about 50 minutes from a 1000VA UPS???
Sounds about right to me but 50 minutes would be a top runtime if constantly idle. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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Anonymoose -
Joined: 09 Sep 2003 Posts: 2192
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Posted: Thu Sep 01, 2005 1:45 pm Post subject: |
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I'd guess 110-120W would be about average for most modern PCs with a couple of HD's while idling...
You'll have to check specific UPS's specifications for the runtime they will provide - the VA rating does not directly relate to the battery life, just how much power it can provide. though I can't see you getting less than half an hour even with a cheap one - it should easily be enough to cope with most short term powercuts; obviously in a long term powercut the advantage of the UPS comes from being able to shut your PC down cleanly using the UPS software to monitor the remaining battery life. _________________
"Invent an idiot proof webserver and they'll invent a better idiot..." |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 01, 2005 1:49 pm Post subject: |
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The longer the uptime the better i suppose. Blackouts in the UK are very rare but one person on my MSN list had one after the horrible thunderstorms last night. He was on his laptop so he was lucky but his server wasnt so.
30 mins should be enough for anyone but any longer is a bonus I suppose. A 1000VA or even a 600VA UPS should do the trick for me. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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Anonymoose -
Joined: 09 Sep 2003 Posts: 2192
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Posted: Thu Sep 01, 2005 1:57 pm Post subject: |
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You'll pay a fair whack for a new 1000VA UPS - if you're willing to chance it, you could save a good £60 and pick a branded APC one up on Ebay. If you go for new, just make sure if it's generic you track down manufacturers specs for the run time.
http://www.dealtime.co.uk/xPC-Trust_800_UPS_Redundant_Power_Supply
Looks like there are some bargains to be had - Trust isn't really top of the range, but they're not generic no name cr*p either. Don't expect that full 60 minutes it promises, but it would be a good compromise between a 650 and 1000VA supply.
Good luck! _________________
"Invent an idiot proof webserver and they'll invent a better idiot..." |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 01, 2005 2:17 pm Post subject: |
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Yeah thanks. Ebuyer had their own make but have sold out. I did have enough at one point but put it off, now they have sold out of their own brand and it was 1000VA for £40 :-(. They also had a 600VA version of £20 :-( which i wanted before they sold out.
I will have to have a look. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 08, 2005 2:06 pm Post subject: |
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Ive just discovered why UPS Systems, even though the same VA vary in price and apprrox uptime so widely...
Its all down to the size of the battery in them. The cheaper the UPS, the smaller the battery will be and therefore the lower the uptime the UPS will support.
A more expensive UPS has a larger battery in it so it will last longer but still support the same amount of power (in VA) but just for a longer time.
Most cheap ones will have a 12v 7Ah lead acid battery in it (the same type I use to run my amateur radio gear) but expensive ones have 14Ah - 32Ah batteries in them.
I discovered this while looking on the maplin electronics site because someone asked and were told 32Ah. This is how some can support 40-50 mins backup time and others only 15-20 mins.
Ive decided on a UPS which is sort of in the middle of the price range. I just have to save up now!
UPS I am hoping to buy: http://www.ebuyer.com/customer/products/index.html?rb=10646450169&action=c2hvd19wcm9kdWN0X3Jldmlld3M=&product_uid=57716 _________________ Andy (AbyssUnderground) (previously The Inquisitor)
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richardyork -
Joined: 22 Jun 2004 Posts: 410 Location: United Kingdom
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Posted: Thu Sep 15, 2005 5:08 pm Post subject: |
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Sorry to bump,
I found something that The Inquisitor may find interesting. http://msdn.microsoft.com/coding4fun/inthebox/powermonitor/default.aspx
If you don't have Visual Studio 2005 and would like it compiled, then I'll post a link here later ;-)
Once again, I'm sorry for bumping this post and I hope it is of some help/interest!!
Thank You _________________ Please SEARCH the forums BEFORE asking questions! |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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Posted: Thu Sep 15, 2005 5:12 pm Post subject: |
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That looks good, thanks, but I'm OK.
Cheers anyway. _________________ Andy (AbyssUnderground) (previously The Inquisitor)
www.abyssunderground.co.uk |
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AbyssUnderground -
Joined: 31 Dec 2004 Posts: 3855
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