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Regarding amps required for a server - Page 2
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Regarding amps required for a server

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Comments

  • @William said:

    @user54321 said: that is wrong. The OPP will trigger normally at ~130% of the rated power on the 12v rail, so depending on the efficiency of the PSU they will draw 135-150% of which the PSU is rated from the wall before they turn off.

    The amp sticker has to account for loss and overload. The Amp stated on the sticker are a finite limit, and there is a legal requirement for them to be correct in EU.

    Than it seems nobody does sell legal computer PSUs in Europe

    example



    Source: https://www.tweakpc.de/hardware/tests/netzteile/corsair_sf750_platinum/s08.php

  • WilliamWilliam Member
    edited April 2021

    Yea, 14.8V should be maximum - My solar system has 58.4V set (/4 = 14.6V per battery)

    @user54321 said: Than it seems nobody does sell legal computer PSUs in Europe

    We talk servers here. Not off the shelf consumer parts.

    Also this PSU has a input rating of 240V*5A = 1200W (or 10A at 120V, also 1200W).

    The sticker is correct and the PSU legal.

    The DC voltage/Amps are irrelevant for regulators, only the wall draw matters.

  • AlwaysSkintAlwaysSkint Member
    edited April 2021

    @user54321 said: Than it seems..

    Arrgh! Why do so many people have difficulty with this?

    @William said: The DC voltage/Amps are irrelevant for regulators, only the wall draw matters.

    I tried that one before but some folks just don't listen. ;)

  • @William said:
    Yea, 14.8V should be maximum - My solar system has 58.4V set (/4 = 14.6V per battery)

    @user54321 said: Than it seems nobody does sell legal computer PSUs in Europe

    We talk servers here. Not off the shelf consumer parts.

    Also this PSU has a input rating of 240V*5A = 1200W (or 10A at 120V, also 1200W).

    The sticker is correct and the PSU legal.

    If you go with that sticker and not the specified curents it tells you nothing, the PSU could draw at max 1200w or 300w because both will be labeled that way. So it tells you exactly nothing if you want to estimate the required amps for your colo.

    @AlwaysSkint said:

    @user54321 said: Than it seems..

    Arrgh! Why do so many people have difficulty with this?

    because reasons, I don't even understand the problem.

  • dfroedfroe Member, Host Rep

    @user54321 said:

    @AlwaysSkint said:

    @user54321 said: Than it seems..

    Arrgh! Why do so many people have difficulty with this?

    because reasons, I don't even understand the problem.

    than != then

    The one isn't just a different spelling of the other one.
    These are two different words with totally different meaning.
    Writing something else then [sic] you mean makes it more difficult for others to read.

    Thanked by 1AlwaysSkint
  • AlwaysSkintAlwaysSkint Member
    edited April 2021

    Let's just read the label correctly shall we?
    AC INPUT (the only relevant part in respect to this thread)
    100V @ 10A = 1kW
    240V @ 5A = 1.2kW
    So the PSU will (nominally) supply anything from 100 to 240V, with a maximum power draw of 1200W.
    If that server is off, uses nothing; if it's idle, who cares. Whilst running flat-out, the server may consume less but only reading real-time current draw will determine that. So the only thing to consider with near certainty is the maximum power draw, assuming a properly labelled, safe PSU. As @William said, put a 5A fuse in it and it can't draw much more - heck, put a 2A one in and listen to it pop when the server gets 'busy'. Good game! :)

    Done & dusted.

    If you want to determine the likely runtime of a UPS on the server, then that is entirely different.

  • skorupionskorupion Member, Host Rep
    1. Don't forget that PSU isn't 100% efficient.
    2. The CPU isn't the only part of the server, you need to factor in EVERYTHING.
  • 1. & 2. Still doesn't grasp it. :-|

    Thanked by 1skorupion
  • jsgjsg Member, Resident Benchmarker
    edited April 2021

    Let's not get lost in over precision. After all input fuses tend to be +10% or 20% on a good day and quite a few major parts (like e.g. the tank inductors) are more like +-20% plus the ADC aren't really precise either, oh, and btw the input fuses usually have reaction times beyond the brown out stay alive times (typ. 10 - 20 ms) but they are meant to serve as worst case last resort (and legally required hence often just formally thrown in) devices anyway. And yes, of course they are utterly un-precise.

    @William said:
    Notably at 210-240V (EU, Asia, anything aside US and Japan anyway) you should buy a 230V ONLY PSU (NOT A 80-280V universal) - Efficiency in Switch Mode Power Supplies (SMPS) is higher the more limited your input voltage is.

    Largely theory (unfortunately).

    Lastly, if you ever need it - All of this PSUs run perfectly fine on 90-230V DC - Chain 6 car batteries and your server will boot just fine. Polarity irrelevant (but should change it at times, to switch the full bridge rectifier to the other 2 diodes, DC will load only 2 always).

    In emergency situations, OK, but generally I'd advise against that because if a device is specified for AC then it should be fed AC. One (of quite a few more) reason: in today's cost/profit optimized world most manufacturers will (ab)use input specs to save tenths of a penny here and there; condensators are a good example.

    That's also why, at least on the prosumer, not to even talk about the consumer segment you'll either not get or pay a leg and a kidney to get a 230V only input computer power supply. They didn't come up with 85 - 250V because they are friendly but because it allows for cheaper mass production, cheaper tested logos (e.g. CE testing) etc.

    And yes that also means that they often sh_t on legal requirements even of major markets like Europe. Example: I've seen quite a few computer power supplies (yes, even newer ones) that gobble up 10W and more in "off" state while the legally required max. is far lower.

  • @user54321 said: So it tells you exactly nothing if you want to estimate the required amps for your colo.

    It tells you the circuit size needed for full load and more relevant - the circuit breaker sizing.

  • AlwaysSkintAlwaysSkint Member
    edited April 2021

    @jsg said: ..that gobble up 10W and more in "off" state..

    The perils of soft switching :( Where's that toggle switch?

    @jsg said: condensators

    That a predominantly American term? Have only heard of condensers before, to refer to capacitors. (I worked in a high voltage electrical lab where testing used to be done on capacitor paper. I used that same paper for other purposes.)

  • jsgjsg Member, Resident Benchmarker

    @AlwaysSkint said:

    @jsg said: ..that gobble up 10W and more in "off" state..

    The perils of soft switching :( Where's that toggle switch?

    Usually at the rear of the computer (where I guess 95% of people don't use it).

    @jsg said: condensators

    That a predominantly American term?

    Nuh, that's a jsg term, mea culpa. You are right, I should have said 'capacitor'.

  • DataIdeas-JoshDataIdeas-Josh Member, Patron Provider

    @yoursunny said:

    @DataIdeas-Josh said:
    To build on top of dual PSUs. It can be used for A/B power.
    In case you have a total power loss say from the grid. You have secondary power from battery/generator.

    @jsg said:
    Nope, that's not how it's supposed to work. Both power feeds to the rack should be UPS'd. The point of a dual PSU is to continue running when either a power feed fails (or is in maint.) or a PSU fails.

    I could plug in two different power circuits, but then I would need twice as many power circuits.
    What a waste!

    It's simpler to just checkpoint the experiment and turn off the server.

    The only time(s) I used the second PSU is when I need to untangle the cords in order to move fibers/ other machines.
    In that case, I could plug in a second cord and unplug the first one.

    It might be more work and more cables however in a DC environment from what I've seen that is how most people run it.
    Granted you can do it via an ATS that works as well but IMO asking for more things to go wrong BUT if have those servers that only have one PSU it gives you the ability for redundant power feeds.
    Just really comes down to how mission critical is your equipment to stay online.

    Thanked by 1yoursunny
  • AlwaysSkintAlwaysSkint Member
    edited April 2021

    @jsg said: Where's that toggle switch?
    Usually at the rear of the computer (where I guess 95% of people don't use it).

    I was being facetious. ;) You're correct in the assessment, I'd imagine. :)
    (Need a long, thin arm to stretch around the back of a 1U or under a desk.)

    Thanked by 1jsg
  • yoursunnyyoursunny Member, IPv6 Advocate

    @DataIdeas-Josh said:
    Just really comes down to how mission critical is your equipment to stay online.

    I run network emulations.
    If the machine is powered off suddenly, the last hour of experiment data is lost, but the experiment will rerun when it's powered on again.

    If I know when I need to unplug the machine, I'd schedule a shutdown earlier.
    It's not about experiment data, but to prevent filesystem corruption.
    A corrupted filesystem means I'll have to spend an afternoon in front of that huge air conditioner, reinstalling the machine.


    There's a mystery in one of the racks though.
    Every other Monday, between 07:30~07:35 UTC, all the machines in that rack would turn off at the same time.
    I found the electrician and they have no idea either.

    Then COVID hits and we had to move the machines to another location so that they are remotely accessible.
    I'd see whether the mystery shutdowns occur again when we get back later this year.

  • @William said:

    @user54321 said: So it tells you exactly nothing if you want to estimate the required amps for your colo.

    It tells you the circuit size needed for full load and more relevant - the circuit breaker sizing.

    :D
    Yeah sure do what ever you want mate it is your money that you throw out of the window for stupid over sized estimations.

  • WilliamWilliam Member
    edited April 2021

    @user54321 said: Yeah sure do what ever you want mate it is your money that you throw out of the window for stupid over sized estimations.

    I see you never worked on a City DC buildout before, you use that high estimate because power density is pure gold in the future and you need it for HVAC sizing also... (+ less copper with 230V anyway, and no 80% rule in most of EU/Europe).

    EDIT: good example is the old Bucharest DC of Voxility (i think they own it or at least occupy much of it, old but ok), you crank that 32A up boiiiii, on up to 3 circuits, 22000W per rack, summer toasty ;)

    Thanked by 2jsg yoursunny
  • user54321user54321 Member
    edited April 2021

    wtf you talk about? this thread is about estimating the power budget of a single server and now you come with buildout of a city DC? why not build your own power plant and plan the power grid for it? That must be very important too for your single server. Yeah sure that is all important but not for you with your single server

  • afnafn Member

    Wow, a lot happened here :o didn't expect my thread to bring all these comments...
    Thanks all for your contributions, I will make sure to read carefully the comments I missed :)

  • AlwaysSkintAlwaysSkint Member
    edited April 2021

    @user54321 said: ..this thread is about estimating the power budget of a single server..

    @William 's point perhaps wisnae clear: people sometimes add things to servers at a later date, for example an additional disc - room for expansion. Hence, the recommendation/advice to use the rated PSU input.

    Thanked by 1yoursunny
  • @AlwaysSkint said:

    @user54321 said: ..this thread is about estimating the power budget of a single server..

    @William 's point perhaps wisnae clear: people sometimes add things to servers at a later date, for example an additional disc - room for expansion. Hence, the recommendation/advice to use the rated PSU input.

    but even than he goes for the "here it will explode" value instead of "here it will shut it self off" value, depending on the PSU the differents between that values can be huge.

  • @user54321 said: but even than ..

    You what?!

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