Sign in with
Sign up | Sign in
Your question
Closed

Split fan power from mobo header to run 2 case fans?

Last response: in Components
Share
June 3, 2011 1:06:12 AM

Is is okay to split the connections from the mobo chassis fan to 2 case fans, using a 3-pin y-splitter?

Will the settings in the BIOS freak out running 2 fans from one header?

My stuff:

Asus P8Z68-V Pro motherboard.
Antec Three Hundred Case, with all fans (2 front HDD fans are the ones in question).
Linkdepot 3-pin Power Y-cable.
Linkdepot 12" 3-pin fan power extension cable.

AND, can I run a 3-pin case fan from a 4-pin chasis header? This would be for the side panel fan for my case.

The Asus mobo has 6 fan headers total, and I would use them all as follows:

2 x 4-pin CPU Fan headers: running 2 CPU fans in a push pull set up, thru the radiator below.
2 x 3-pin PWR headers: (1) running a RAM fan, and (2) a Antec Kuhler H20 620 Liquid Cooling System pump.
1 x 4-pin Chassis Fan header: running a 3-pin Antec Tri-Cool fan, mounted to the side panel of my case, with the ext.
1 x 3-pin Chassis Fan header: running 2 x Antec Tri-Cool fans, with the above splitter, for the front fans of my case.

This leaves a 140mm Antec Tri-Cool fan, on the top of my case, runing off of a molex connector from the PSU. All Antec case fans can run off the the mobo headers, or molex connectors from the PSU.

Any other set up recommended?

Best solution

June 5, 2011 10:43:40 AM

foscooter said:
Is is okay to split the connections from the mobo chassis fan to 2 case fans, using a 3-pin y-splitter?

It really depends on the fans and the motherboard header. If you draw too much power from a single header, it might burn out, so you should check on maximum amperage per fan header on the motherboard manual. Only two high-amperage fans should pose trouble, however.

foscooter said:
Will the settings in the BIOS freak out running 2 fans from one header?

Well, the fans should be identical, so you can know what to expect. If you have both a low-rpm and a high-rpm fan at the same time, one of them might not even start up, which you want to avoid.

As far as the BIOS goes, make sure the splitter only supplies the yellow (RPM/Sense) wire to ONE of the fans. If both fans are reporting RPMs using the same wire, BIOS fan speed readings will be all over the place, or the report will be zero, which most BIOSes interpret as no fan attached, which might lead to a POST error code or a failed boot.

foscooter said:
AND, can I run a 3-pin case fan from a 4-pin chasis header?

Yes, you can. 3-pin fans are 100% compatible with 4-pin headers, and generally speaking the 4-pin header is keyed so as not to damage the motherboard or fan if a 3-pin fan is incorrectly connected. Do keep in mind, though, that you might loose fan speed control with that setup.

Just to clarify, there are BIOSes and/or I/O controllers that are able to control fan speeds when PWM is used (PWM is basically a fast on/off switch), but can't do it the "old way" (voltage-based control, meaning you slow down a fan by dropping the voltage from 12V down to whatever you need), meaning a 3-pin fan will ALWAYS run at max speed. Or you might need to fiddle with the BIOS and set the way RPM control is to be handled (RPM or voltage). Either way, if you have a 4-pin header, I'd cough up the extra $5 for a PWM fan, unless even when using a 4-pin fan it always spins at maximum speed (it might happen, there are pretty crappy I/O controllers and BIOS out there... lol)


foscooter said:
The Asus mobo has 6 fan headers total, and I would use them all as follows:

That seems a decent configuration.

You may want to run SpeedFan to determine which headers are software-controllable, though. If all of them are controllable, you might be able to do some pretty nifty things, like slowing down the pump (and other fans) when the rig is idling, or just ramp up the RAM fan for a spot cool. SpeedFan is WAY out of topic, though, I don't want to go overboard here.

Hope this helps.

Miguel
Share
June 5, 2011 6:42:29 PM

Thanks Man! Thanks for the details, too.

If I do split 2 case fans, they are identical Antec Tri-Cools. I'll also look into PWM Fan to the connnectors using 4-pin headers.

I'll check out the SpeedFan app when I'm up and running next weekend.
Score
0
Related resources
June 5, 2011 6:42:38 PM

Best answer selected by foscooter.
Score
0
June 5, 2011 10:05:02 PM

You're welcome, I'm glad to help.

Those Tri-Cools, if memory serves me right, have a speed selector, right? If so, you will be able to control them even if they end up connected to a permanent 12V header, so you should shift stuff around if you end up with limited headers.

Btw, memory, even when overclocked, doesn't draw that much power, nor does it heat that much. You shouldn't need, at most, more than a slow-spinning fan over it.

Good luck, and let me know how that rig turns out, ok?

Miguel
Score
0
June 11, 2011 4:28:05 AM

Pulled the original case fans, and one added Tri-Cools fan. Running the 2 front fans with a splitter off the mobo header, and I DID cut one of the yellow wires to one of the fans. The mobo reads it at 1000+ rpm which is fine!

Running a 120mm PWM fan (side panel) AND a 140mm regular fan (top) thru a splitter, plugged into the mobo. But this spliiter only had 2 wires to one of the splits. Fan runnings at 1000+rpm (Side panel).

So, so far so good. Having other issues with the new rig.....
Score
0
June 11, 2011 4:33:13 AM

This topic has been closed by Mrface
Score
0
!