Connecting Two Fans to One Motherboard Fan Header

[tbird2340]

I have one motherboard fan header and two 80mm case fans I want to hookup to it..

Question is.. Is it OK to do this? The reason I want to use the fan header instead of a molex is because of the RPM sensing / automatic temperature control.

If I splice the two fans (power to power, ground to ground, rpm to rpm) into one wire of each and plug that into the board will I get correct RPM sensing and will it safely power both fans?

Thanks!

 

[krotchy]

I wouldn't recommend splicing the RPM sensors together, because you probably wont get any useful information. However if they are identical fans, monitoring one should reflect 2.

As far as splicing power and gnd together, as long as the current draw of the 2 combined isnt more than the mobo can handle, you will be fine. Check the manual to see what current the fan header can give, and compare it to the watt rating of the fans (Watts/12V = Amps)

 

[tbird2340]

If I only monitor one fan then will it only control one fan? Or since the power/gnd will be spliced together if it wants to speed up / slow down the fans it will affect both?


Also, my motherboard (Biostar Geforce 6100-M7) doesn't mention anything about the current...

Thanks for the reply.

 

[krotchy]

Since 3 pin motherboard headers regulate fan speed based on voltage alone, the 2 fans, assuming they are matched will be identical in speed. Again this is assuming that the motherboard can handle the current draw of 2 fans.

 

[zagood]

In general, motherboard headers are anywhere from 4-6 watts. 80mm fans are around 1.5-2.5 watts. Check your fans, if they're under 2 watts each I'd personally say you'll be fine. Any more than that and you're looking for trouble.

If you can track down the actual motherboard output, obviously, that would be the safest way to go.

-z

 

[aigomorla]

can you tell us what fans your intend to run?

I mean if your talking about 2 deltas at full blast, then hellz no its not safe. you'll most definitely burn out that header.

If your dropping small low spin fans, then i dont think there should be a problem. I have 2 60mm fan headers spliced off one to keep my mosfet cool.

Also i would take the advice about the rpm sensor.

 

[skillyho]

I had two 80mm Mascools (30CFM) running off of a single 3-pin header on a Biostar TForce6100-939 board for well over a year until I switched cases....never had any problems. Like others have said, as long as you don't go full tilt with some crazy rpm's you should be fine.

 

[jonmcc33]

I wouldn't do it. The only reason you should use motherboard connectors are for smaller fans (chipset, CPU) anyway. Just plug it into the PSU with a 4-pin molex.

 

[SirFelixCat]

Originally posted by: jonmcc33
I wouldn't do it. The only reason you should use motherboard connectors are for smaller fans (chipset, CPU) anyway. Just plug it into the PSU with a 4-pin molex.

Didn't want to start a new thread since this is essentially the same ??? I have.

I have the new CM 830 Stacker case and have 4 - 120mm fans on the door. The case has a total of 8 possible 120mm fans (not using them all, just saying I could if I want to), and my mobo (IP35-Pro) has 6 fan headers (including the CPU one).

Could I splice 2 Yate Loon SM fans together (only power and ground) or should I just skip plugging them into the mobo all together and just go w/ the PSU 4-pin molex and let them go at full speed 24/7? The 'noise' isn't an issue to me, so if it's possible to do this, that'd be fine w/ me.


One more thing: I also have the PC Power & Cooling 750w Quad PSU and all the power runs on one big rail. So, with that in mind, couldn't I connect all 4 fans from the side panel in series and then just have one 4-pin molex connected to the PSU to power all 4 fans or should I not do this?

TIA.