AF120 and AF140 on one header?

Sammy43

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Sep 8, 2014
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Hey all,

So I have a gaming rig and I'm wondering if I'm good to run 1x AF120 and 1x AF140 on the one pwm header? I know they're 3 pin but I know you can run 3 pin fans on a pwm header and I would run both using a y splitter.

Also wondering if I'll be able to control 2 fans on the one header using voltage control? And will they both be able to run at full speed or is the voltage shared?

I'm new to building PC's and still learning all this stuff.

Thanks,
Sammy43
 
Solution
Probably won't work, but might, for reasons not given above.

First of all, YES, you can connect two such fans to one SYS_FAN header using a Y-splitter. Those fans' specs say they consume 0.13 amps (each) when running, which is in the "normal" range for case vent fans. So two will consume 0.26 amps, and might take up to 3x that (0.78 amps) for a few seconds during start-up. Almost all mobo SYS_FAN headers these days can supply up to 1.0 amps at 12 VDC, and hence the "rule of thumb" that you can connect UP TO 2 fans to a fan header, but not more. Two fans connected in parallel to a header both receive the same voltage, but consume twice as many amps as one fan.

Now the problem. You say you have 3-pin fans which can ONLY be controlled by...

Not a good idea. To know whether it will work or not you'll need to locate the controler chip and associated circuitry and determine if it can handle the current that two fans would draw. If it's not engineered to handle the current of two fans you'll burn up the controller and/or some of the associated components.


It's not about voltage but current. Current affects voltage and vice versa so it depends on the specific circuit you will use.
 


Thanks for quick reply. I have other options but this would've just made my life a little easier, but I'll just go to plan b.

Thanks again.
 
Probably won't work, but might, for reasons not given above.

First of all, YES, you can connect two such fans to one SYS_FAN header using a Y-splitter. Those fans' specs say they consume 0.13 amps (each) when running, which is in the "normal" range for case vent fans. So two will consume 0.26 amps, and might take up to 3x that (0.78 amps) for a few seconds during start-up. Almost all mobo SYS_FAN headers these days can supply up to 1.0 amps at 12 VDC, and hence the "rule of thumb" that you can connect UP TO 2 fans to a fan header, but not more. Two fans connected in parallel to a header both receive the same voltage, but consume twice as many amps as one fan.

Now the problem. You say you have 3-pin fans which can ONLY be controlled by a SYS_FAN header operating in Voltage Control Mode. Usually that means the header must be of the 3-pin design. However, there are exceptions. Some mobos actually allow you to set, in the fan configuration options in BIOS Setup, whether the 4-pin SYS_FAN header(s) operate in PWM Mode or Voltage Control Mode. Some others have installed "fake" 4-pin headers that actually operate as true 3-pin headers in Voltage Control Mode with an unused 4th pin. But MANY mobo SYS_FAN headers with 4 pins actually are true 4-pin headers that operate only in PWM Mode, and that can NOT control a 3-pin fan's speed. A 3-pin fan on that header type can only run full speed all the time.

So whether or not you can do as you want depends on the details of your mobo's SYS_FAN headers. If you can't figure that out from the manual (and many are confusing!), post back here exactly what mobo you have and we can advise.
 
Solution