Adding Case Fans

[Brolller]

So right now I am extremely confused on what to do. I'm going to be building a pc and the case I will be using, the Nzxt s340 has 2 fans pre installed. I was thinking of just connecting these two to the 2 fan headers on the Asus Prime b350 Plus (This motherboard does have 2 places to connect 2 3pin fan cables right?).

Anyways because I will be using the Gtx 1080 it was recommended to me to add 2 more extra fans. Problem is the 2 "fan" slots have already been used up on the motherboard so do I connect the rest of the 2 fans to the PSU.

Basically what I'm asking is "CAN YOU HAVE 4 FANS IN A CASE AND CONNECT 2 TO THE MOTHERBOARD AND 2 TO THE PSU?" Is this a thing?

Sorry if this is a noob question but I would really appreciate it if someone told me how and where to connect these 4 fans? Also hoe does one connect a 3 pin fan cable to a PSU

The two extra fans I will be using will be the Be Quiet! Pure Wings 2 140mm

I'm freaking out and don't know how to do this so could somebody please explain this to me?!

 

[Scottray]

Super easy - you just need to buy 2 fan splitter cables. Something like this; https://www.amazon.com/PWM-Y-Splitter-Cable-Adapter/dp/B002OFP6QW.
Note that the fan headers on your mobo are probably 4 pin, however these are also compatible with 3 pin fans. So, depending on your fans, you'll need either 3 pin fan splitters or 4 pin fan splitters. DON'T mix a 3 pin fan and a 4 pin fan on the same splitter. It may not work.

 

[Paperdoc]

Scottray has the right answer - two Splitters. You can use each to connect two of your fans to a single mobo CHA_FAN header - 2 headers with splitters = 4 fan connections.

More details. The fans supplied with that case are of the 3-pin type. Your mobo's CHA_AFN headers can be configured to work properly with them (later). So I suggest that any additional fans you buy also be of the 3-pin type just to make things easy. And Scottray is right - do not mix 3- and 4-pin fans on the same splitter / header.

3-pin fan splitters are getting hard to find, but 4-pin splitters will also work just fine for you. When you use the, the fans simply won't connect to the 4th pin. Make sure you get a Splitter, and not a Hub. The one Scottray linked is the right type. Note in the photo that it has one female input connector (with holes) to plug into the mobo header and two output male (with pins) connectors for the fans, and NO other arms. A Hub (you don't want) has an additional third arm type that must plug into a PSU power output.

Look at your mobo's manual on p. 2-6 for the EZ Mode screen of BIOS Setup. Click at bottom centre on "QFan Control" to get to fan configuration. The manual does not show you that screen. But you will have to choose which fan header you are configuring, and then work on EACH of your two CAH_FAN headers. For each you should set it to use "DC" mode for control, and not "PWM". DC mode is necessary for 3-pin fans. For now, let it use its default fan performance curve. IF there is a choice to be made about which temperature sensor to use for controlling these case fans, select the one on the Motherboard, not the one inside the CPU chip. When you're done, use the F10 key to get to the exit menu and then be sure to SAVE ande EXIT to save your new settings and reboot.

Doing things this way will power AND control the speed of all four case ventilation fans automatically, according to the temperatures inside the case.

 

[raisonjohn]

So right now I am extremely confused on what to do. I'm going to be building a pc and the case I will be using, the Nzxt s340 has 2 fans pre installed. I was thinking of just connecting these two to the 2 fan headers on the Asus Prime b350 Plus (This motherboard does have 2 places to connect 2 3pin fan cables right?).

Anyways because I will be using the Gtx 1080 it was recommended to me to add 2 more extra fans. Problem is the 2 "fan" slots have already been used up on the motherboard so do I connect the rest of the 2 fans to the PSU.

Basically what I'm asking is "CAN YOU HAVE 4 FANS IN A CASE AND CONNECT 2 TO THE MOTHERBOARD AND 2 TO THE PSU?" Is this a thing?

Sorry if this is a noob question but I would really appreciate it if someone told me how and where to connect these 4 fans? Also hoe does one connect a 3 pin fan cable to a PSU

The two extra fans I will be using will be the Be Quiet! Pure Wings 2 140mm

I'm freaking out and don't know how to do this so could somebody please explain this to me?!

Your NZXT S340 comes with two 120mm fans (the NZXT FN V2) which are 3-pin fans rated at 0.16A each. The be quiet! Pure Wings 2 (140mm) you wish to add are 3-pin fans (non-PWM version) and are rated at 0.09A each.

Your Asus Prime B350 Plus does have 2 extra fan headers (CHA_FAN1 and CHA_FAN2), apart from the CPU_FAN. Those 2 extra fan headers are 4-pin fan headers, which can be configured in BIOS (Asus Q-Fan Control) or Software (Asus Fan Xpert 2) to be PWM or DC/non-PWM modes.

PWM mode uses the 2nd pin to provide constant +12V to power the PWM fan and uses the 4th pin to provide variable current (pulse modulation) to speed up or slow down such fan based on temperature. DC mode uses the 2nd pin to provide variable voltage to power the non-PWM fan and, often, doesn't use the 4th pin electrically/electronically.

Physically, 4-pin headers accept both 4-pin cables or 3-pin cables by just aligning the tab spanning Pins #1, 2, and 3 like this:

Now, you have several options to mount 4x total fans in your case, with a motherboard only having 2x available fan headers.

OPTION 1: Using Splitters
The fan headers on a typical motherboard are rated at 1A max. So, this means that plugging several fans drawing a total ampere below that rated current is doable. For safety, you want the total amp draw of all the fans running off of one header to be about ~75% of the header's amp rating (which is 0.75A).

Knowing that your 2x NZXT FN V2's draw 0.16A each (total of 0.32A), and the 2x be quiet! Pure Wings 2's draw 0.09A each (total of 0.18A), you can safely plug the 2x NZXT's running of CHA_1 header and the 2x be quiet's running of CHA_2.

You achieve this by using a 2-way fan splitter cable such as this: https://www.amazon.com/Splitter-Extension-Sleeving-Connectors-Length/dp/B00C46DX4S

In fact, theoretically, you can even plug all 4x case fans (NZXTs at 0.32A + be quiet!s 0.18A) totalling to 0.5A safely off just one header using a 4-way fan splitter or "hub" such as this: https://www.amazon.com/DeepCool-FAN-HUB-Cooler-Powers/dp/B008YD7B0M/ref=sr_1_1?s=electronics&ie=UTF8&qid=1499482673&sr=1-1&keywords=deepcool+hub

Though, it is not advisable to mix different fan models (due to different rpm/speeds and airflow) to have consistent readings on your temp/speed percentage. What the splitter does is just detect/read the first fan's speed and adjusts the other fans' speed according to percentage of that first fan. So, for example, you mixed two different fans on a splitter (the first fan having a max. 2000rpm and the other fan having a max.1200rpm), your motherboard's fan header will only read the "2000 rpm" of the first fan. If such header is adjusted using a fan curve to have the fans connected to it spin at 50% on a given temperature, the motherboard will report to you that such header is running "1000 rpm" when it reaches that temperature. However, in reality, since you mixed 2 different fans, the first fan is in fact running 1000rpm (50% of 2000rpm), but, the second fan is running 600rpm (50% of 1200rpm) - which is not accurate as to what is being displayed to you by the motherboard.

In short, keep same fans on groups of splitters for consistent readings.

OPTION 2: Plugging some fans on the motherboard and some fans on the PSU
As above, you can just power one fan off of one header of your motherboard. Such header will report to you the actual speed of the fan connected to it. Since your motherboard only has 2x available headers, you can plug the other 2x remaining fans directly to your PSU by using a 3-pin-to-Molex adapter cable such as this: https://www.amazon.com/ExtremeMod-Computer-Connector-Y-Splitter-Adapter/dp/B00DU8ZZ0O/ref=sr_1_3?s=electronics&ie=UTF8&qid=1499483343&sr=1-3&keywords=3-pin+to+molex

The difference between running the fans via the motherboard and via the PSU is that the former can change the fan speed based on temp curves and report to you the speed while the latter means running the fans at full speed 24/7 without any speed monitoring (since it'll always run 100% full).

This is safe to do but other builders prefer to have control over the fan speed especially the noise levels. If noise doesn't concern you, then plugging the case fans directly to the PSU can be an option.