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Question about power limits on PWM fan headers

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Nereus
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2021/05/31 10:46:46 (permalink)
 
Hello. I will soon be setting up a Z590 FTW rig. I notice in the manual a warning in red bold all caps:
 
"ALL FAN HEADERS HAVE A MAXIMUM POWER LIMIT OF 2AMP @ 12 VOLTS (24WATTS). EXCEEDING THIS LIMIT WILL CAUSE IRREPARABLE DAMAGE TO THE BOARD."
 
Ok. I'm not an electrical engineer so please can someone check this out for me, because I seem to have confused myself:
 
I'm planning on plugging in the 3 PWM intake case fans on a triple splitter into one motherboard PWM fan header. The fans are Corsair LL120 RGB fans which draw 0.3A and operating voltage is 7-13.2V (13.2V being on 100% rpm). AFAIK, Amps x Volts = Watts, so 0.3A x 13.2V = just under 4W on full speed per fan. Based on this data;
3 fans would be 3 x 4W = 12W which is fine
3 fans would be 3 x 0.3A = ~1A which is fine
3 fans (on full speed) would be 3 x 13.2V = ~40V which apparently is not fine... but I think I'm doing something wrong here, because even one fan is rated up to 13.2V which is more than the stated 12V warning... so which part matters? The Watts, the Amps, or the Volts - I'm guessing Volts don't add up cumulatively? Sorry for my ignorance, just got myself a little confused, particularly when I've run 2 fans on a splitter in many builds. ..or is only the total Amperage that matters?
 
 
 
post edited by Nereus - 2021/05/31 10:58:25


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    Sajin
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    Re: Question about power limits on PWM fan headers 2021/05/31 13:29:27 (permalink)
    Amps is all that matters.
    #2
    Nereus
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    Re: Question about power limits on PWM fan headers 2021/05/31 14:50:55 (permalink)
     
    Awesome, thank you.
     
     


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    ty_ger07
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    Re: Question about power limits on PWM fan headers 2021/05/31 20:52:25 (permalink)
    If you use the right splitters (powered splitters), the fans will use nearly zero amps from the header and you can plug in nearly an infinite number of fans into one header.  Everyone should use a powered splitter all the time, in my opinion.  That way you never have to worry about it no matter how many times you change your fan decisions.
     
    For example:

     
    I have 5 Delta fans (~4 amps peak total) running on one 4-pin PWM header. ;)
    post edited by ty_ger07 - 2021/05/31 21:01:51

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    Nereus
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    Re: Question about power limits on PWM fan headers 2021/06/03 03:37:43 (permalink)
     
    Thanks again for the responses, much appreciated. The triple splitters I have aren't powered, but the intake fans only use 0.3A each, so well within spec. Also turns out my new Corsair 5000X case has a PWM repeater hub for up to 6 fans which is very handy - I'll run all 6 radiator fans through there (2 x 360mm radiators) and just a single PWM header needed on the motherboard to control the speed of them. Nice.
     
     


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    #5
    bossmanbossman
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    Re: Question about power limits on PWM fan headers 2021/06/07 18:03:04 (permalink)
    This thread helped me out
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    leelawrencecs
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    Re: Question about power limits on PWM fan headers 2021/06/08 13:04:49 (permalink)
    just look at the amps
    #7
    103JL
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    Re: Question about power limits on PWM fan headers 2021/06/14 17:10:57 (permalink)
    look at what amps? where?
    #8
    Nereus
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    Re: Question about power limits on PWM fan headers 2021/06/14 21:24:40 (permalink)
     
    On the fan specs, and on the motherboard specs.
     


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    Nozler
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    Re: Question about power limits on PWM fan headers 2021/06/15 16:49:40 (permalink)
    Ran into this issue with Delta fan Amp draw to much on a X-58 had to intall
    a Sunbeam fan controller from the psu.
     
    Ah Deltas they can melt the ol MB down melt the ol MB doouwn.

    heatware
     
    #10
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