[SOLVED] Fans + Fractal Define 7 XL Nexus+ 2 fan hub

[lesm1l]

Hello guys.

I would like to ask a question about PWM fans & CPU cooler fan. I just bought my first PC parts and I am going to build it in next few days (I’ve always been using laptops). The question is regarding these parts:

PC Case: Fractal Design Define 7 XL
Motherboard: Asus ROG Crosshair VIII Hero (WI-FI) ATX AM4
6x PWM fans: be quiet! SilentWings 3 PWM High-Speed
CPU Cooler: Noctua NH-D15 CHROMAX.BLACK

• CPU cooler connector will go to CPU_FAN – will use 2 fans so 2x L.N.A. will go to 4-pin PWM Y cable, and that cable’s connector will go to CPU_FAN on motherboard. Right?
• Then I will use 6x PWM fans (3x front, 2x top and 1x rear) – the thing is, that I want to have all of these fans on same RPM every time. And here comes the part I am not sure of:
• a.) Should I buy some fan splitters (I have found only 1-4pins to 2-4pins splitter NOCTUA NA-SYC1 Chromax White)? I would connect 3 of those splitters into Fractal’s Nexus+ 2 fan hub like on this pisture
• b.) If it is ok to connect 3 fan splitters into this hub (so I would sacrifice connector for Main/CPU 4-pin PWM fan)? Where should the yellow connector go to – as CPU_FAN slot will be taken by Noctua NH-D15 should it go to CHA_FAN1 or to H_AMP connector?

Thank you very much for your help. And I apologize for such a lame post.

 

[Karadjgne]

1. No need to use the LNA, low noise adapters, you can specify what fan curve you want in bios, like Silent mode etc. This gives the option for full range of 12v rpm, not limited to a 9v rpm. Just use the included Y splitter straight to the cpu_fan header.
2. 1 header = 1 speed. So if you connect all 6 fans through the hub, all 6 will operate at the same rpm as set by the motherboard/software connection at the header. The exception is some hubs use USB not fan headers, so can operate multiple speeds.

I'd use a single 3way splitter for the front 3 fans, a 2way for the top fans and leave the rear exhaust by itself. This'll help with wiring as the groupings are seperated.

 

[lesm1l]

First of all, thank you very much for your reply and help. So CPU + MoBo is solved (no LNA, going to CPU_FAN).

About 6x fans I am still a bit confused. For what you suggested (3x front to 3way splitter going to one header, 2x top with 2way splitter going to second header and 1x rear exhaust going to to last header), I have found two splitters:

3way splitter: EK-Cable Y-Splitter 3-Fan PWM (10cm) (1x4 PIN male and 3x Females – which only 1 is 4PIN, two of them are 3PINs)
2way splitter: EK-Cable Y-Splitter 2-Fan PWM (10cm)

be quiet! SilentWings 3 PWM High-Speed Be Quiet! SILENT WINGS 3 140mm PWM high-speed fans have information about (A) like this:
Current consumption (A) - 0.14
Safety current (A) - 0.5

I would say 6 fans should use 0.5x6=3 A (and not 0.14x6=0,84 A), is that correct (I am not really sure, sorry)? Well, for 3 front fans it should be 1,5A, two at top 1A and rear 0,5A. I might decide not to use Fractal Hub, so I could connect them directly to MoBo so I would like to ask which header should this 3 front fans cable go, please (MoBo headers details):

A) CHA_FAN1 (max 1A) + CHA_FAN2+CHA_FAN3 (3x front – 2x top – 1x rear)
B) H_AMP + CHA_FAN1 + CHA_FAN2 (3x front – 2x top – 1x rear)

And is it ok to connect 3way & 2way splitters to another cable extension like this CableMod ModFlex™ 4-pin Fan Cable Extension 30cm , please? I would like to have it looking nice with cablemod cables tho

Thank you very much again.

 

[Karadjgne]

Splitters can get confusing with wire counts. But they way they work is through the header. There's just 1 header and it has 4 pins. Ground, 12v, speed sensor (tach) and pwm signal. Of those 4, only 3 actually do anything. Ground and 12v obviously, but the tach only reports the speed of the fan. The pwm signal is what tells the fan on/off pulse. Being as there's only 1 header, there's only 1 tach, so a splitter will have a master and bunch of slaves. The master is the 4 wire, it will send the tach info back to the motherboard, but the pwm signal goes to all the fans simultaneously. You see it as 2, 3, 4 fans spinning, but the header sees that as a single fan. So software doesn't control the fans, it controls the header. You can unplug any fan and it still works as normal, but unplugging the master will show as 0 rpm. With some software, cpu_fan header this'll set off low rpm warnings.

There's plenty of different companies that make splitters, they all work the same way, but you can also use a powered splitter, which uses 12v from the psu (molex or Sata) and not the 12v from the motherboard, allowing upto @ 10 fans (that's the limit of the pwm signal strength being split up) on a single header.

The hub is similarly powered, so you can use splitters however you like, power not coming from a header, comes from the psu directly. Only the pwm signal being split limits you to 10 fans. Only requirement is that you must follow the master connector and have 1 fan on it.

So you can have a header, with 4way splitter, master 2way splitter, 3x slaves with 2way splitters and have 8 fans on 1 header, the original 4way being powered. Which is a lot of wires but equates to exactly what a hub does. You power the hub, the hub powers the fans, the pwm signal is split up to control all the fans as a single unit reporting back to any header.

Fan headers have a 1A limit for continuous loads. The safety limit on the fans is for the initial startup spike, but that's temporary, you'll use the running amperage. So if you want, you can use a powered 4way for the front 3 fans, master and 2x slaves, and eliminate the header amperage limit. The 2way splitter will not be an issue, neither will the single rear exhaust. Run to 3x different headers, this will give control over seperate zones, rear, top, front, which is what any software will see, not 6x individual fans. This will allow for the motherboard zone sensors to change fan rpm for that zone as needed and allows you to tailor the zone rpm curves as wanted.

 

[lesm1l]

@Karadjgne Thank you very much

 

[Karadjgne]

No worries, good luck and happy building!