Three Fans Connected to a Single Fan Header?

[domchu]

Hi everyone,

 

Earlier today I installed two sets of three fans using two EKWB 3-way fan splitters onto my ROG Z390E Gaming motherboard:

 

- 3x be quiet! Silent Wings 3 120mm PWM High-Speed (0.16A / 0.37A safety current, 1.92W) as intake.

- 1x be quiet! Silent Wings 3 120mm PWM High-Speed, 2x be quiet! Silent Wings 3 140mm PWM High-Speed (0.14A / 0.5A safety current, 1.68W) as exhaust

 

I'm confident that a single fan header can power three fans, they even ran at full speed without fail for a few seconds when I was playing around with BIOS settings (I run them at quite conservative speeds normally), the total amperage of three fans don't exceed the 1 amps a fan header can supply.

 

However, I have some concerns:

 

1 - on be quiet!'s website, they list the 'safety current' which is 0.38A and 0.5A for the 120mm and 140mm models respectively, which combined well exceeds 1 amp. I'm not sure what exactly 'safety current' is, and i haven't been able to find much information.

 

2 - I've seen a bunch of Reddit threads on the same topic where people say that fans use 'more amperage when starting up'. Which isn't very specific since it would either be: they start up using their maximum operating amperage (which would be fine), or they exceed their maximum operating amperage for a brief moment. Again, I don't know.

 

I've been able to run my PC normally after the installation, the fans start up as normal and they are all operating normally. I'm just making this post as a sanity check. Any comments explaining concerns 1 and 2 would be greatly appreciated.

 

- Dom

[RejZoR]

I'm gonna go against it from acoustic perspective. For some reason I've had weird resonating issues when hooking PWM fans to a single header. I don't know what's going on, but I think the PWM pulses make fans run in sync which causes bizarre resonating noise that drives me insane. It's like fans are pulsing with acceleration and deceleration within few 10 RPM or something. Haven't fully figured it out yet, but my case fans were doing this until I hooked them to a fan hub. And now Liquid Freezer II cooler with 2 fans is doing this gain coz it's powering them internally from the same header again. I'm splitting them tomorrow and my suspicion is that it'll stop doing that.

 

SATA fan hubs are cheap and reliable solution to run many fans from one header since it's only for PWM speed, power comes from SATA. It's how I run 4x SilentWings 3 140mm on my case. I don't have good experience with Y splitters. Fan hubs on the other hand worked great for me.

[RejZoR]

Yup, rewired it today and the oscillating noise disappeared entirely. It seems when many identical fans are hooked to the same header, they get same PWM pulses that seem to get amplified in rather horrible way. Only way I can think of why this happens. My ASUS Strix X570-E has 3 headers for CPU cooling, CPU Fan, CPU Fan Optional and CPU AiO Pump. Yours too, but it has them split apart.

 

I'm using Liquid Freezer II 240 having its main wire plugged to CPU Fan and both fans on it run from that single CPU Fan header. Meaning 1 header was running AiO pump, AiO VRM fan and 2x 120mm radiator fans. And it had the annoying oscillating background "woooom" noise in identical intervals at higher RPM making it insanely irritating.

 

I see your motherboard has 7 fan headers. I suggest you use them instead of splitter cables or utilize fan hub for same groups of fans (like 1x fan hub for all intake and exhaust fans, but not anything related to CPU.

 

The way I'd use them is the following (see labels on the image of the motherboard):