How many fans can I run off a single sys/cpu fan header?

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ali13245

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hello everyone, So I recently purchased 12 case fans for my rig upgrade, and I was wondering if I would be able to run 4 fans with 3 splitters on each of the sys/cpu fan headers on my motherboard which is an MSI Z97 Gaming 7. Basically l'm trying to find put what the amp limit is on the headers for my motherboard seeing as I cannot find any answer in the motherboard manual. The fans are 4x corsair sp120, 4x corsair af120, and 4x corsair af140. I did some math according to the specs of the fans, and I found out that 0.4A was the highest of the 4 af140 fans combined @12V. The other 8 fans were rated at 0.64A @12V being the highest, so when splitting those to 4 fans it becomes 0.32A @12V
 
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Your setup should work, but I would consider using a fan controller or maybe a fan to molex adapter to make sure your motherboard is not getting more than it can handle.
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ali13245

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Thanks for the reply! :) the problme I have with using a fan controller is that it bulky and ugly, and just ruins the look of my build, and I am trying to achieve the cleanest look possible. So should I go ahead and proceed with what have I planned and used the motherbaord headers?
 
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photonboy

photonboy

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Hi,
First of all, I don't follow your math. The equation is:
Power (Watts) = Current (Amps) X Voltage (Volts), or P=IV

The maximum power simply ADDS as the amperage at the same RPM won't change and the voltage is set at 12V. FOUR fans use 4X the power as one fan.

Also, I'm not sure why you need twelve fans but it's possibly too many. Perhaps you're trying some push/pull combination with 2x2 fans per radiator?

I'll try to find out the actual information but for now I'd err on the side of two fans only per header.
 
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BrandonYoung

BrandonYoung

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Oct 13, 2014
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Using two parallel fans via splitter on a single motherboard fan header will draw twice as much amps as a single fan. If your fans are each 0.64A @ 12V, using two fans on a single motherboard fan header will draw 1.28A @ 12V, not 0.32A @ 12V.

You can drive as many fans as you want on your motherboard fan header, AS LONG as you're not drawing more amps then the header was intended to output. After a bit of searching, a common value I've found is 1 amp (12 watts @ 12V) motherboard fan headers. Your results may vary.

 
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photonboy

photonboy

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FAN NUMBERS:

He confused me at first because I assumed a single fan (as did the other guy). He also made a MISTAKE when adding up his fans. He did get the 4xAF140 results correct though (0.4A total). Here's the proper results:

Max values:
AF120-> 0.13A
SP120-> 0.18A
AF140-> 0.1A

Proper math:
Simply add the max values for the fans you actually intend to have on each header.

For example, if he's mixing then it's:

Total (max) Amperage = 2x(0.18A) + 2x(0.13A)

= 0.62A

*So this is less than 1A and should be fine.

(Note that this is the max value for FOUR mixed fans, not eight so the OP made a mistake somewhere.)
 
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ali13245

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Sorry for the confusion, perhaps its my fault for also not mentioning that all the fans are quiet edition, so the numbers that photonboy got are higher than what they are supposed to be. What I meant before is that 4 x sp120 (Quiet Edition) draw a TOTAL of 0.32A MAX, as well as 4 x af120 (quiet edition) draw a TOTAL of 0.32A MAX, thats how I got the previous numbers, It is my fault for not clarifying enough. The af140 fans are also quiet edition and the numbers for it are right, So moving on with these numbers, all should be good right?
 
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