2 fans on the rad

[CompTech]

I have what probably is a question with a simple answer but good `ol Google isn't helping much today. I have an Antec Kuhler H2o 620 currently running in a stock configuration with 1 fan set up in a pull air flow situation. The fan is running off the pump lead.

My question is what is the best way to power a dual fan set up? I got the fans from Newegg today that I am going to use in a push/pull air flow config, XigmaTek 120x25mm HSF-F1252. These babies are 90cfm and quiet. They have 3 pin leads with a 3 to 4molex adapter. Should I get a splitter and run them both off the pump lead...plug them into mobo 3pin headers...or use the molex adapter and run them from the PSU? I have PWM turned on in bios. Will that matter?

Appreciate the advice.

[James]

If they are 3 pin leads, they are not PWM fans. Instead they are the old school fans. You can find 3-pin Y splitters. One side of the Y only has 2 wires (red, black + & -), the other side has all 3 wires. (Red, Black, Yellow, yellow being the rpm sensor). This is done to keep the controller from being confused by two rpm feedbacks. The y-splitter only costs a few dollars. Other than that, you could run one off the motherboard and another off of the pump, but that will probably end in a horrible noise as each fan is run at a different speed.

By running them on a Y splitter they will be (as much as possible) running at the same RPMs, and won't make any resonance noises.

[CompTech]

Anything I can find has all 3 wires to both tails. I spose I could just pull the yellow RPM lead from one tail. Would it be possible to then run them both off the pump lead? The pump itself is connected to the 4 pin CPU fan header which is PWM enabled in bios. I assume there is circuitry in the pump housing that then controls voltage to the fan depending on cpu load. Im just wondering if it would be safe to run 2 fans off the 3 pin pump lead.

[James]

Anything I can find has all 3 wires to both tails. I spose I could just pull the yellow RPM lead from one tail. Would it be possible to then run them both off the pump lead? The pump itself is connected to the 4 pin CPU fan header which is PWM enabled in bios. I assume there is circuitry in the pump housing that then controls voltage to the fan depending on cpu load. Im just wondering if it would be safe to run 2 fans off the 3 pin pump lead.

Yes. But you don't want both fans reporting RPM (via that yellow wire) back to the controller (in this case, your pumps fan header). If all you are doing is running raw power the fans, that's fine. But if you have something that is actively trying to manage the fans speed (like the controller in your pump), you don't want to be reporting two different RPM readings simultaneously when the controller expects one. Pretty much any cheap y cable will have the yellow rpm wire running to both fans. You can give one of those a try. It will set you back roughly $3-$5.

[CompTech]

Done deal. I found one on my supply of goodies. Ill just pull the RPM lead out of one tail and run them both off the pump lead. Thanks for your help.

[CompTech]

Update....running both fans off the pump lead minus one yellow rpm lead to one of the fans. Working great and I can't hear any significant odd noise indicatiing different rpms. Can barely hear the 25db fans at all. The push pull set up with the new fans bought me another 3c cooler temps than the stock fan that came with the kit in a pull config.