# 2 fans off 1 header?



## Deleted member 24505 (Apr 23, 2019)

is it ok to run 2 fans of the same type off 1 motherboard fan header?


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## HUSKIE (Apr 23, 2019)

Yes it is. I have 3 fans and 1 pump in 1 Motherboard 4 pin fan header.


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## infrared (Apr 23, 2019)

Yep, unless they're really high power server fans they should be fine, the mobo manual should mention somewhere what the max rating is, iirc it's usually about 1Amp per header which is quite a lot when it comes to fans. I bought the connectors and crimp up my own y leads, just missing off the RPM signal wire from one, so far I've never had any prob running 2x 120mm EK vardar or corsair ML fans off a single header. 


HUSKIE said:


> Yes it is. I have 3 fans and 1 pump in 1 Motherboard 4 pin fan header.


Wow, I'm actually quite impressed it's managing that, goes to show i guess.


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## IceShroom (Apr 23, 2019)

tigger said:


> is it ok to run 2 fans of the same type off 1 motherboard fan header?


Yes, if combined power of two fans dont exceed 12W power.


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## HUSKIE (Apr 23, 2019)

infrared said:


> Yep, unless they're really high power server fans they should be fine, the mobo manual should mention somewhere what the max rating is, iirc it's usually about 1Amp per header which is quite a lot when it comes to fans. I bought the connectors and crimp up my own y leads, just missing off the RPM signal wire from one, so far I've never had any prob running 2x 120mm EK vardar or corsair ML fans off a single header.
> 
> Wow, I'm actually quite impressed it's managing that, goes to show i guess.



Yeap on my fractal design celsius s36 it has 4 4pin hub stick into the rad and connected straight to the pump from pump to mobo header.


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## Sasqui (Apr 23, 2019)

IceShroom said:


> Yes, if combined power of two fans dont exceed 12W power.



I recall one MB manual specifically stating the wattage limit on the fan headers, and that number rings a bell.

Edit, blast from 2011, someone saying an ASUS X58 board can put out 2A (24w):  https://www.techpowerup.com/forums/threads/multiple-fans-on-same-header.145295/post-2277037


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## IceShroom (Apr 23, 2019)

Sasqui said:


> I recall one MB manual specifically stating the wattage limit on the fan headers, and that number rings a bell.
> 
> Edit, blast from 2011, someone saying an ASUS X58 board can put out 2A (24w):  https://www.techpowerup.com/forums/threads/multiple-fans-on-same-header.145295/post-2277037


Well most motherboards fan header support 1A. Though some board support more power as you mentioned.


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## AsRock (Apr 24, 2019)

Yes, just make sure you stay away from the max amps on the motherboard fan header.  To find out what that is you might have to contact the manufacture.



IceShroom said:


> Well most motherboards fan header support 1A. Though some board support more power as you mentioned.



Personally i would not go over that, better safe than sorry.


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## John Naylor (Apr 24, 2019)

Is it OK to drink a bottle eat 6 candy bars ... kinda depends on how big those bars are 

Your header is likely rated for one amp.  A typical 140mm 1250 rpm case fan is rated for about 0.14 amps.  You probably should account for inrush current but the manufacturers already do that, well at least some do, so not that big of a worry most of the time.   Some high end boards will have one or mor 2A headers.

So, again, using that typical 140mm 1250 rpm fan @ 0.14 amps.

I have a  420 rad in push / pull and my logic went like this.

1250 rpm fans ... use 83% of header rating to account for inrush current
1500 rpm fans ... use 75% of header rating to account for inrush current.
1800 rpm fans ... use 67% of header rating to account for inrush current.
2200 rpm fans ... use 58% of header rating to account for inrush current.

Again, the way most control schemes go these days, they ramp the speed up to minimize inrush and there's a bit of beefiness built in to handle inrush anyway so I would not be too concerned if ya exceed that with modern fans / MoBos.  

So, for my 420 rad w/ twin 140mm 1250 rpm fans in push pull, my target was 0.83 amps.  
6 fans on 420 rad x 0.14 = 0.84 amps ~ 0.83 OK

They been spinning 24/7 for 5.5 years.   Well not really, all fans turn off when CPU temps are < 40.  When load is applied they ramp up over about 30 seconds and ramp down over 90 when load is removed so as to clear latent heat from coolant.... that perty much eliminates any inrush concerns and the fanms nver break 850 rpm anyway.

I recommend hubs over splitter cables, hubs are less messy and cables market is loaded with poor quality sudd.

You need different types of devices to do this:

a)  DCV fans w/ DCV header - 3-Pin Male to 3 x 3-pin Male or 3-Pin Male to 5 x 3-pin Male
No aux power should be used
http://www.modmy.toys/pcb.html 

b)  PWM fans with PWM header 
If exceeding 1 amp, can use aux power connector
https://www.swiftech.com/8-WayPWMsplitter-sata.aspx

c)  DCV Fans with PWM **or** DCV Header
Use up to (6) DCV (0.14) fans with full speed control from PWM header and no aux power
Use up to (8) DCV (< 1.0 amp total) ) fans with full speed control from PWM header with aux power
Use up to (6) DCV (0.14) fans with full speed control from DCV header and no aux power
https://www.newegg.com/Product/Product.aspx?Item=N82E16811984004


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## Deleted member 24505 (Apr 24, 2019)

Thank you for all replys.

so I can wire the 2 x 4 pin Corsair AF 140 on one header with just one rpm wire connected?


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## John Naylor (Apr 25, 2019)

Well there are a few versions ....

DCV Air Series™ AF140 Quiet Edition High Airflow 140mm Fan = 0.10amps
https://www.corsair.com/us/en/Categ...flow-140mm-Fan/p/CO-9050009-WW#tab-tech-specs

DCV Air Series™ AF140 LED (2018) White 140mm Fan Single Pack = 0.30 amps
https://www.corsair.com/us/en/Categ...se-Cooling-Fan/p/CO-9050085-WW#tab-tech-specs

http://www.performance-pcs.com/modmytoys-3-pin-power-distribution-pcb-3-way-block.html

This PCB may requires you to manage the rpm thing for 2nd fan yaself ....
https://allpinouts.org/pinouts/connectors/motherboards/motherboard-cpu-3-pin-fan-connector/

With this one, it's all done for you inside the PCB
https://www.newegg.com/Product/Product.aspx?Item=9SIA4RE5032993


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## Kissamies (Apr 26, 2019)

I have 2x Corsair ML120 and 2x be quiet! PWM fans with both twins using one header with a splitter. No problems.



tigger said:


> so I can wire the 2 x 4 pin Corsair AF 140 on one header with just one rpm wire connected?


Yes.


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## Deleted member 24505 (Apr 26, 2019)

John Naylor said:


> Well there are a few versions ....
> 
> DCV Air Series™ AF140 Quiet Edition High Airflow 140mm Fan = 0.10amps
> https://www.corsair.com/us/en/Categories/Products/Fans/Air-Series™-AF140-Quiet-Edition-High-Airflow-140mm-Fan/p/CO-9050009-WW#tab-tech-specs
> ...



I think i might look for a fan hub or controller with some sort of rpm display. All together I have 6 140mm fans in my case.


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## John Naylor (Apr 26, 2019)

I have a Reeven Six Eyes which i used just to display cooalnt temps (rad 1 In, rad 1 Out, rad 2 in, rad 2 out, Ambient and case interior.   The most common usage is to use it as a manual fan controller .... you turn the knobs and manually control rpm ,  I have not tried it just displaying the rpm, but don't see why it couldn't be done.  Would require some extra wiring thoi

But why bother ? FanXpert 2 comes with the MoBo (On the DVD that came in the box) .... watch the video

h*ttps://www.youtube.com/watch?v=4i-aTUMuIB0

Copy / paste the link into your browser window and then delete the asterisk between the h and the t


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## HUSKIE (Apr 27, 2019)

I have these fan hubs


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## John Naylor (Apr 27, 2019)

1st one looks like  Molex or 4 pin DCV (no yellow wire)  input and six 3 pin DCV outputs

2nd one could be a 4 pin PWM input (but I don't see a yellow wire) to 3 pin DCV with 12v aux power.  The white connector sends back the rpm signal.  

3rd one looks like Molex to  .... (this is an odd one)

4 x 3 pin fan (7 - 12v)

... 2 x 4 pin DCV  (5 - 12v)
... 4 x 3 pin DCV  (5 - 12v)
... 4 x 3 pin DCV  (12v full speed only)


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## lexluthermiester (Apr 27, 2019)

tigger said:


> is it ok to run 2 fans of the same type off 1 motherboard fan header?


Yes. Fans don't draw a bunch of power and it is safe to run 3 or 4 from one header. However...


HUSKIE said:


> and 1 pump in 1 Motherboard 4 pin fan header.


...this is really pushing it. Pumps do need a lot of power. Such a power draw might cause issues long term.. Try not to do this. Give a pump it's own dedicated connector.


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