Understanding splitters for case fans . . .

[mallozzi]

Hi Guys,

I recently built a Pc and I'm interested in adding one case fan to my set up and could use some advice.

I'm currently using a Corsair Air 240, and I want to add two white-LED ML120's up front (or AF120/SP120) which would mean that the two fans that are currently there would need to be moved/removed. I know how to replace and relocate the fans, what I don't know is how to power them.

All of the fans in my current system are 3 pin fans and all of the ports on my motherboard are 4 pin style. My motherboard has three different system-fan outlets so I imagine that I would need some kind of splitter? This is the motherboard I'm currently using: http://ca.gigabyte.com/Motherboard/GA-Z97M-D3H-rev-11#ov

Should I be buying a 4 pin splitter or a 3 pin splitter? (does it matter?) Does the extra power draw from an LED effect anything?

 

[DRagor]

If all your fans are 3pin, no need to buy 4pin splitter, 3 pin splitter will do. If you buy 4pin fan(s), use 4 pin splitter for them. But you only need splitter when trying to connect more fans then your mobo has headers.
LEDs draw so small amounts of power that it does not affect anything.

 

[vdorta]

I just finished building my fifth PC and had to use a splitter for the case fans. By the way, I first ordered the cheap Chinese one offered in Newegg but it didn't work; I then ordered the https://www.amazon.com/JBtek-Black-Sleeved-Splitter-Converter/dp/B00OZ10FI2/ref=sr_1_4?s=pc&ie=UTF8&qid=1492710152&sr=1-4&keywords=pwm+fan+splitter black sleeved cable on Amazon and it works OK. Your motherboard has 1 cpu and 3 case fan connectors; you don't say how many case fans you have in total, but supposing they are three, you don't need a splitter. I recommend 4-pin (PWM) fans because the fan speed can then be controlled in the BIOS (I did a cursory check and only the Corsair ML120 appears to be 4-pin). If you have, say, a total of 4 case fans, you'll have to use a splitter in one of the three connections. Check the total electrical load l if you have to use more than one splitter.

 

[Paperdoc]

You are right to pay attention to matching fan type to mobo header type. Unfortunately, you can't tell from the pin count of a mobo header what it uses for actual control technique. But since you posted you actual mobo we can look at its manual. On p. 13 its diagrams show that the CPU_FAN header uses PWM Mode, but the three SYS_FAN headers all use Voltage Control Mode. This latter is exactly what you need for 3-pin fans, although it can also control 4-pin fans. Since you have 3-pin fans and plan to replace them with other 3-pin fans (maybe), that will all work out.

As a practical reality, both 3-pin and 4-pin fan SPLITTERS will work equally well for 3-pin fans. But I find often that you can't find 3-pin Splitters, so 4-pin ones are just fine for your purpose.

Among the three fan models you listed (assuming you want white LED models in all cases) the ML line can produce higher max air flows but at higher noise levels, and they are all 4-pin PWM fans, and the most expensive of the three. (That design can work well with Voltage Control Mode, but it's not quite ideal.) They are marketed as more durable because of bearing design. The SP120 line (3-pin type) is less expensive and quieter, but also deliver less air flow. You don't need the "high static pressure" feature for case ventilation fans, so the AF120 line (3-pin type also) is suited better. However, that line appears to be available only in the Quiet Edition version that runs quieter because it runs slower and delivers even less air at max than the SP120 line.

One thing to keep in mind regarding air flow and noise. If you have your case fans under automatic control by the mobo SYS_FAN headers, they will reduce the fan speeds to whatever air flow is required to keep your system temperatures on target. So using the ML fans which CAN run noisier and deliver more air flow at max speed does NOT mean they will actually run that way in your system. When they are slowed down to deliver the SAME air flow that one of the others might do, their noise level will also be reduced. But if ever your system is under heavy use and needs a lot of cooling, the ML120 line units will deliver more air at their max speed.

You need to be aware of a limit on power. Most mobo SYS_FAN headers can supply up to 1.0 amp total current to all the fans connected to that one header. Now the specs for those fans you are evaluating show they consume 0.3 to 0.4 amps each (more than a fan alone, because of the LED's included). So you would be safe to use two such fans via a Splitter on one header, and more fans could be combined on a separate header and splitter. You have three headers to use, so that should work.

When using a device to combine two fans to one header using Voltage Control Mode, you must use a SPLITTER, and not a HUB. Unfortunately, I often see some Hubs sold under the term "Splitter" when they are not. How to tell? Well, a SPLITTER has one arm ending in a female (with a line of holes) connector that plugs into a mobo SYS_FAN header, and then two (or three) output arms that each end in a male (with pins) connector. You plug your fans into these. All of the fans get their power from the SYS_FAN header in this way. A HUB has an extra arm that must plug into a power output from the PSU (either a 4-pin Molex, or a SATA power output). Power for all its fans comes from the PSU, and not from the SYS_FAN header. A SPLITTER does not have this extra arm going to the PSU. The trouble is that a HUB can only work to control the speed of 4-pin fans using PWM Mode for control. You do not have that control system in your SYS_FAN headers, so you MUST use a SPLITTER for your system.