# Multiple fans on same header



## theubersmurf (May 6, 2011)

Is there a way to determine the Amperage available on a single fan header to determine if it can viably support a pair of fans via a splitter. Come give me your best guess. I can't find specific information in my motherboard manual or on the manufacturer's website about it, however, It strikes me that the amperage of fans is pretty variable between fans, and that motherboard makers probably provide overhead based on that, such that if the fans were reasonably low amperage they'd be easily able to work using the same header.


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## Dippyskoodlez (May 6, 2011)

Dual 80's and 120's is probably fine from one header, but I would first suggest considering just clipping the wire, and making it longer to reach other motherboard headers. Most have 4-6 headers, or just obtaining Molex->3 pin adaptors.

Overloading a section of your motherboard could have very catastrophic results.

The 3 pin splitter is probably intended for direct PSU connections.


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## BazookaJoe (May 6, 2011)

Yeah - the average 12V fan draws very very little current in relative terms.

There should be no problem running 2 or even 3 fans off of one connector - not that I'd recommend it, I'm just saying there is in all reasonable probability , very little actual risk, unless you are using NON spec fans IE : Fans that WHERE NOT intended / or sold / as PC fans.

You can, for example, get 12cm 12v fans in electronic stores with motors over 1.2A - and those should NOT be connected to your motherboard fan headers, however if you are using "PC" fans - then go ahead.

At the same time I would agree with Drippy - if there is ANY OTHER WAY, DO THAT FIRST. Using things OUTSIDE of their intended design parameters is always a bad idea - even if it DOES work.

And remember too - You may share the VOLTAGE of one header with 2 fans - but you cant share the "probe" - that is to say the (Usually Yellow Or White) wire that reports fan SPEED to the board - if you join that as well - you will just get garbage readings - you need to chose ONE fan to use as the probe.

Taking it even further,  Sharing is only probably going to work on STANDARD 3 wire fans - normally red, black, and yellow - the 4 wire PWM fans - like Intel's stock coolers should never be shared - as it is highly possible to blow the PWM chip ( Pulse Width Modulator)

EDIT : I have 2 Standard Gigabyte case fan's that come fitted in cases as stock cooling in their budget cases,  (8cm) is rated at 0.12A and (12CM) is rated at 0.20A - Adding up to 0.32A which _should_ be within tolerance, but try and keep it under 0.5A - just for sensibility's sake


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## slyfox2151 (May 6, 2011)

under 1.5amps should be fine..... i have run 2amp fans on the CPU fan header with no problems on a gigabyte and asus board.


(those delta fans really move some air.... and loud as fuck lol.)


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## BazookaJoe (May 6, 2011)

slyfox2151 said:


> under 1.5amps should be fine..... i have run 2amp fans on the CPU fan header with no problems on a gigabyte and asus board.
> (those delta fans really move some air.... and loud as fuck lol.)




I will DISAGREE with this strongly - MANY of the modern boards use PWM chips even on their standard header ports that are rated WELL below 1.5A even if some better *cough* gigabyte/asus *cough* boards *CAN* handle it, I would personally NOT AT ALL consider it safe to assume that every other manufacturer would.

But that's just my 10c


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## mm67 (May 6, 2011)

All fan headers on my Asus X58 Sabertooth and Rampage Gene III boards are rated for 2 A according to manuals. That means for example 5 GT AP-15 fans on one header (0.36 A startup current) or 9 GT AP-14's (0.21 A startup current). PWM headers are even better with Akasa PWM splitters since those only take PWM signal from header but power to fans comes from a Molex connector.


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## Bundy (May 6, 2011)

if you have a PWM header it would be safer to take the power direct from the PSU and only use the signal from the mobo. You would look pretty dumb if you really did burn out a mobo to run heaps of fans...not worth it. Note : I am runnung 2 x 120mm PWM fans off one header lol it seems ok for that.
If you don't have a PWM header, then just run the fans off the PSU anyway.


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## claylomax (May 6, 2011)

theubersmurf said:


> Is there a way to determine the Amperage available on a single fan header to determine if it can viably support a pair of fans via a splitter. Come give me your best guess. I can't find specific information in my motherboard manual or on the manufacturer's website about it, however, It strikes me that the amperage of fans is pretty variable between fans, and that motherboard makers probably provide overhead based on that, such that if the fans were reasonably low amperage they'd be easily able to work using the same header.



I use this: http://www.scan.co.uk/products/akasa-ak-fy320-3pin-female-to-2-x-3pin-male-(fan)-splitter-cable The two fans on my cpu cooler run at the same speed all the time controlled by the motherboard. I had to change a setting in the bios under cpu fan from PWM to DC, otherwise they would run at full speed. EDIT: Most fans won't start below 5v


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## Jetster (May 6, 2011)

Dont run more that one. Theres no reason to. Use your PS. Even if its rated for it its causing more connections and more resistance = heat.


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## theubersmurf (May 6, 2011)

Both were identical Scythe PWM fans rated at .51amps. But as someone pointed out, the motherboard is getting a garbled signal from the fans, so they're running at full speed all the time with the splitter. This is actually a large part of why I ditched this, because the two fans running at 1900 RPM provided me with a chorus much louder than I wanted. Besides, running it at 3.5GHz day to day is fine, the push pull configuration doesn't matter that much, I can live with the overclock I have. Thanks for all of the input everyone.


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## mm67 (May 6, 2011)

theubersmurf said:


> Both were identical Scythe PWM fans rated at .51amps. But as someone pointed out, the motherboard is getting a garbled signal from the fans, so they're running at full speed all the time with the splitter. This is actually a large part of why I ditched this, because the two fans running at 1900 RPM provided me with a chorus much louder than I wanted. Besides, running it at 3.5GHz day to day is fine, the push pull configuration doesn't matter that much, I can live with the overclock I have. Thanks for all of the input everyone.



This is what you need to run multiple PWM fans from one header : http://www.akasa.com.tw/update.php?...es&type_sub=Fan Cable Adapters&model=AK-CB002


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## LAN_deRf_HA (May 6, 2011)

I run two 3pin y splitters on my evo. One for two AP15 equivalent fans on a controller, and the other two are 750rpm 140s. Those last two use less power than some single fans. It's safe certainly for your average fan, but some performance fans use radically more power. So I'd always try to find specs for your fans. I wouldn't even bother using a fan header period on a budget board besides the cpu one.


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