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PSU How to tell if PSU is overloaded?

Discussion in 'Hardware' started by Bitwacker, 13 Dec 2012.

  1. Bitwacker

    Bitwacker C# forever

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    Hello,

    How do you tell when a power supply is overloaded or close to max?

    Do you have to test it at the wall? Are cheap the testers reliable?

    What are the symptoms if a PC is drawing to much?
     
  2. rollo

    rollo Well-Known Member

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    Most people buy psus that are double or tripple what there pc draws from the wall.

    Most psus will auto shutdown once they hit a certain level, there's no real way to test.

    Your rig in sit would use no more than 400 watts though.
     
  3. azrael-

    azrael- I'm special...

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    That's probably a correct assumption. However, it's how this wattage is distributed that is interesting. These days you need as much power on the 12V rail(s) as possible. The 3.3V and 5V rails don't matter much any longer.

    Bitwacker, which PSU are you currently using (make and model)?
     
  4. mm vr

    mm vr The cheesecake is a lie

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    That's the absolutely best way.

    Reliable and accurate enough for this.

    The fan in the PSU usually gets pretty loud after 70-80% load is reached.

    Your system should pull around 300W on full load and 100W on idle. Get a power meter and check it yourself. :thumb:
     
  5. mrbungle

    mrbungle Undercooked chicken giver

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    They smell bad when they are overloaded lol
     
  6. Elledan

    Elledan New Member

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    First thing to look at is whether you have a quality PSU. A cheap, generic PSU or one of a fail brand is likely to be overloaded or harming your PC even at lower loads. Assuming you bought a quality PSU, you can add up the max TDPs for the parts in your system as a quick start, then if you want to know more you can use a power meter as suggested above. I use the power draw reported by my APC UPS to know that I'm still far below what my PSU can handle :)

    Do note that for a power meter on the AC side you have to subtract the part which is lost as heat during conversion. This number differs depending on the efficiency of your PSU, but is generally above 80%.
     
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  7. Bitwacker

    Bitwacker C# forever

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    Your last point is interesting. If I understand correctly (which I may not), then a 650W supply will only create 650 * 80% = 520W of usable power?
     
  8. azrael-

    azrael- I'm special...

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    Pretty much, yes.
     
  9. TaRkA DaHl

    TaRkA DaHl Well-Known Member

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    It's the other way round, they will create 600w at the plugs in theory, but will draw a bit more at the wall socket.
     
  10. Deders

    Deders Well-Known Member

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    If it is well built enough then it will be able to supply 650W, but will draw 812.5W from the wall to do so, at 80% efficiency.
     
  11. Bitwacker

    Bitwacker C# forever

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    Got it. Thanks.
     
  12. Sam__

    Sam__ Active Member

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    This is correct.

    Here is a link for anyone wanting to know how much their rig pulls - http://extreme.outervision.com/psucalculatorlite.jsp
     
  13. mm vr

    mm vr The cheesecake is a lie

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    No, that will calculate what kind of a power supply Thermaltake, a PSU manufaturer, recommends. If it suggests 400W, then a 400W unit is all you need, and your rig will pull around 200-250W.
     
  14. Sam__

    Sam__ Active Member

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    I don't see any thermaltake mentioned anywhere on that page?

    edit:
    It looks like Thermaltake and Antec use the page to help users. Surely if two major companies use it can't be too inaccurate.

    And it all depends on how you define how much it will "pull". Are you taking ALL components at 100% usage? or just an average usage?
     
    Last edited: 17 Dec 2012
  15. mm vr

    mm vr The cheesecake is a lie

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    There's a conflict of interest. PSU manufacturers want users to buy more expensive units. Of course they recommend a calculator that benefits them.

    Well, actually that calculator is rather accurate, the results are just misunderstood. The result is the recommended wattage of the power supply, not the power draw of the system. In other words, the result already includes some "overprovisioning". If the result is "400W", it means a 400W power supply is the recommended size.

    All components fully loaded.

    The system in my sig pulls around 330W from the wall on full load (Prime95 + FurMark), and the 4870 is quite power hungry compared to newer cards.

    edit: Wow, I just tried that calculator once again. They've changed it. It recommended 390W for my setup, while previously I've seen numbers in the 500s. I guess it's not that bad after all.
     
    Last edited: 18 Dec 2012
  16. Sam__

    Sam__ Active Member

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    I did wonder why you were so extremely opposed. I have found it fairly accurate as you did when you used it yesterday. I do understand that they may have a conflict of interest but I think it's acceptable they add 20% for safety.

    On a side note I've always wanted to buy a plug in power meter to see what my rig takes from the wall.
     
  17. faugusztin

    faugusztin I *am* the guy with two left hands

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    Oh yeah, sure, fairly accurate. 346 minimum, 396W recommended for my setup according to the calculator. Except it uses 240W at the highest load :rolleyes:.
     
  18. Sam__

    Sam__ Active Member

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    Did you fully load it up? It's easy to load up the CPU and GPU, people can think their done then. Spindle HDDs can take up a fair wattage when running and other peripherals can add up too.

    I'm not saying the calc is 100% accurate, just one needs to consider every single component in your case and outside your case (e.g. usb devices).
     
  19. faugusztin

    faugusztin I *am* the guy with two left hands

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    Yes, OCCT + Furmark at once, and yes, i added everything needed - and it is off by a lot. As it was always.
     
  20. Sam__

    Sam__ Active Member

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    Fair enough. I just wanted to make sure.
     

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