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 Post subject: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 12:44 pm 
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Joined: Sat Jul 10, 2004 12:24 pm
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Location: US
I've seen PWM fan splitters that have an auxiliary power input to run as many as five PWM fans off of one fan header. But I was wondering how safe it is to run two PWM fans from one header using a splitter without additional power?

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 Post subject: Re: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 1:19 pm 
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I would say it's totally fine to run two fans off one header.

I have 2x TY-140 fans on my CPU from just the one fan header using the splitter you linked.

I also run 2x 92mm fans off one case fan header.
My video card has 2x 92mm fans off its fan header, then it did have 2x 80mm very high speed fans as stock.

Regards, Seb

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 Post subject: Re: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 1:19 pm 
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Depends on how many watts they pull. I suspect your are probably safe as long as you keep the total wattage under 5 watts. Here is some test data that shows you how much it can vary from fan to fan:

http://www.xbitlabs.com/articles/cooler ... html#sect0

http://www.xbitlabs.com/articles/cooler ... html#sect0

http://www.xbitlabs.com/articles/cooler ... html#sect0

http://www.xbitlabs.com/articles/cooler ... html#sect0

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 Post subject: Re: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 1:39 pm 
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Thanks for the links to the xbit articles.

I was considering placing two Scythe Slip Stream 1300 RPM PWM fans on one header so that I might use another mobo header for a bottom fan in a Define Mini case. I'm not sure if they'd ever be run at full speed. I doubt it.

One odd thing I notice in the xbit article: They measure a Slip Stream 12M @1170 RPM at 14.2 CFM, while the Slip Stream PWM @1050 RPM pushes 19.1 CFM of air. If they're the same size and have the same blade design, how can that be?

http://www.xbitlabs.com/images/coolers/ ... fm_xbt.png

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Motherboard: ASUS P8Z77-M PRO CPU: Intel i5-3750K CPU Cooler: Scythe Mugen 3 Rev.B Memory: G.Skill Ares DDR3 1600 16 GB
Boot Drive: Samsung 830 SSD 128 GB Work Drive: WDC WD1001FALS 1 TB 7200 RPM Optical Drive: Samsung SH-222BB DVD-RW
Case: Fractal Design Define Mini Fans: 2 x FD 120mm front, Scythe 120mm PWM rear Power Supply: SeaSonic M12II 620


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 Post subject: Re: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 2:21 pm 
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Location: US
JJ wrote:
One odd thing I notice in the xbit article: They measure a Slip Stream 12M @1170 RPM at 14.2 CFM, while the Slip Stream PWM @1050 RPM pushes 19.1 CFM of air. If they're the same size and have the same blade design, how can that be?
http://www.xbitlabs.com/images/coolers/ ... fm_xbt.png
The is the 12mm thick slipstream - mucho different fan blades

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"Aristotle calls man the rational animal. All my life I have been seeking evidence to confirm this" Bertrand Russell
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 Post subject: Re: Multiple fans on one motherboard fan header
PostPosted: Thu Jul 19, 2012 2:24 pm 
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Joined: Sat Jul 10, 2004 12:24 pm
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ces wrote:
This is the 12mm thick slipstream


Ah, I didn't catch that. Yes, big difference.

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Boot Drive: Samsung 830 SSD 128 GB Work Drive: WDC WD1001FALS 1 TB 7200 RPM Optical Drive: Samsung SH-222BB DVD-RW
Case: Fractal Design Define Mini Fans: 2 x FD 120mm front, Scythe 120mm PWM rear Power Supply: SeaSonic M12II 620


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