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2 fans in one mobo header

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September 23, 2010 12:38:07 PM

Hello guys...... i have gigabyte GA-p55-usb3 mobo which was the following fan headers - one 4-pin CPU fan header, one 4-pin case fan header and two 3-pin case fan header (well one is for the psu fan but i'll use it for a case fan).

I was wondering if i can connect two PWM fans (for case) into one 4-pin case fan header using a split connector and still achieve PWM control with the correct volts reaching both the fans or the voltage will be split and the fans would be getting only half the intended volts.

More about : fans mobo header

a b V Motherboard
October 12, 2010 5:05:31 PM

I believe (on a whim here) the voltage would end up splitting. I'm seeing it like if it was a USB port splitted into two. Might still work, but the power is less. So performance is lost.

It might be best to just buy an adapter for the second one and go molex - OR - buy a fan controller and just plug both fans into it and control them individually =)
a b V Motherboard
October 12, 2010 5:10:30 PM

Worst that could happen imo is that you melt the header from drawing too much current :)  and potentially damage other parts of your mobo because of the heat
I personally wouldn't advise doing it but be careful if you do man
Moto
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a c 716 V Motherboard
October 12, 2010 5:43:22 PM

I never use any of the MOBO CASE_Fan headers, and always use either a Fan Controller {4 channel minimum} or the PSU with a Molex adapter.

"Y"'ing off case fans is not a good idea: 1. creates "dirty" power feedback to the MOBO, 2. takes unnecessary power from the MOBO, 3. 'can' cause problems if AMPs are exceeded/header {varies by MOBO - see manual.
a b V Motherboard
October 12, 2010 7:54:57 PM

The voltage will NOT split (it will remain 5V or 12V). The board will simply have to output TWICE the power it normally would in this case. This might cause a problem for the board.

Look in the manual to see if you can find out how much current (amps) those ports are rated for (i.e. 0.5A, 1A, 100mA). The fans should also list how much power they consume (i.e. 12V, 0.5A). The port would need to be able to provide enough power for both fans (so two 0.5A fans means the board needs to be able to supply 1A on that port). If these numbers add up, you should be good to go. If the port can't supply enough amps, you'll have problems, and risk damaging the board if you attach two fans.

Additionally, most Y-adapters are only 3-pin connectors (and usually only run 2 wires). This means you won't have PWM and you won't have speed monitoring. This is because you can't monitor the speed of two fans on one port, and if you aren't monitoring fan-speed, you don't need PWM (thus, the port will run at 100% all the time). Therefore, connecting two to the motherboard would be like connecting two directly to the power supply through a molex adapter, only you put undo stress on your motherboard.

I would just connect them to individual ports or use a molex adapter. You won't gain anything with what you're trying to do.
a c 716 V Motherboard
October 12, 2010 8:14:12 PM

Keep in mind, I build expensive rigs for a variety of uses; 'my objectives' are OC, quality, Best Practices, etc. I could make this post really complex but it would read like manual.

Example: of 'unnecessary' noise going straight into your MOBO, devices {sound}, etc. You don't want these signals going into your build.
a b V Motherboard
October 12, 2010 8:30:55 PM

jaquith said:
Keep in mind, I build expensive rigs for a variety of uses; 'my objectives' are OC, quality, Best Practices, etc. I could make this post really complex but it would read like manual.

Example: of 'unnecessary' noise going straight into your MOBO, devices {sound}, etc. You don't want these signals going into your build.
http://upload.wikimedia.org/wikibooks/en/d/d8/Noisespectrum.gif

^+1 interesting graph there mate x)
October 13, 2010 10:03:36 AM

I'm not planning to use the power supply for the PWM fans from mobo since they are designed for one fan use only (at least technically). I'm only gonna use 4 Control blue connection from my mobo's 4 pin fan header (the mobo has a seperate 4 pin system PWM fan header apart from the 4 pin CPU PWM fan header) to connect to the case fans (so that they are temp controlled by mobo). And the power for the case fans from the PSU (it requires only the 1 GND black and 2 12 V Yellow. This is daisy chained.

The splitter i have in mind is linked below.

http://www.newegg.com/Product/ImageGallery.aspx?CurImag...


Let me know your feedbacks
a b V Motherboard
October 13, 2010 2:02:12 PM

Well powering them separately might be better? lol.

Personally I would just use a fan controller. Motherboards are not always very good with controlling fans automatically. Even if i connect them to the mobo, i still set the speeds afterward in the OS to higher ones. And i think a fan controller is easier to work with. And with all the ones out there you can get one with temp reading (and temp-control). That's what i did =). then i rewired all the cabled (modded it into my case) so you can't see any wires going to the fan controller or the fans, though that's optional lol. But something like this could work. Just saying.

If you want that splitter, you can try it - there's only one way to know for sure if it'll work xD
a b V Motherboard
October 13, 2010 5:42:12 PM

abully said:
I'm not planning to use the power supply for the PWM fans from mobo since they are designed for one fan use only (at least technically). I'm only gonna use 4 Control blue connection from my mobo's 4 pin fan header (the mobo has a seperate 4 pin system PWM fan header apart from the 4 pin CPU PWM fan header) to connect to the case fans (so that they are temp controlled by mobo). And the power for the case fans from the PSU (it requires only the 1 GND black and 2 12 V Yellow. This is daisy chained.

The splitter i have in mind is linked below.

http://www.newegg.com/Product/ImageGallery.aspx?CurImag...


Let me know your feedbacks


Ah, I see what you're doing there now. The only question I have is if the Case fan PWM header modulates (the manual for your board only mentions modulation on the CPU header). To get that cable splitter to work, you might have to connect it to the CPU Fan PWM header, and connect both case fans AND your CPU cooler to the splitter. Otherwise, if the motherboard does not regulate the Case Fan PWM header, both fans will run 100% all the time.

It really might just be best to get a controller like the others are saying. But since you aren't powering the fans through the motherboard, I don't see any risk in trying that splitter.
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