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How many fans per header?

Bandalo
Level 7
I'm putting together a build with this X99 board, and I'm trying to figure out a clean way to connect the fans.

I have 6 fans (push/pull on a 360 radiator) in the front, and 4 (push/pull on a 240 radiator in the rear). I'd like these fans to operate in 2 groups, so that all the front fans spin the same speeds, and all the rear spin the same speeds.

The fronts are PWM Vardar F2's, (1450rpm, 12V @ 0.73W), so a total of about 4.38W. The rear's are Typhoon AP-14s (0.6W, 2.4W total), NON-PWM.

I'd like to have all 6 connected with a splitter to one chassis fan header on the MB, and then all 4 connected to a second. Then use the BIOS or s/w to control the fan speeds with CPU temps.

How realistic is this scenario? I know the headers in theory can each handle 1A/12W, but I'm concerned with starting currents and damaging the headers on the MB.

Also curious about how ASUS implements their fan control. I've heard some headers are true PWM, and some use DC control. How will this work with the NON-PWM fans?
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13 REPLIES 13

kkn
Level 14
MAX 1 amp per channel.
mabye a lill less becouse it takes a lill more power to start the fans.

Bandalo
Level 7
The Vardar's should draw about 0.06A each, for 0.36A total. Even allowing for starting surge, that SHOULD be enough. But I've always found "in theory" sometimes results in real-world damage.

Korth
Level 14
I have 6 NF-A14 industrial on my top 420mm rad, 12V 0.18A each at full spin.
All six fans together would pull 1.08A 12.96W, and the RVE should be able to easily power them across two 1A/12W PWM outputs. But I found they tended to stop and stutter and had to be spread across three mobo outputs. Been looking for self-powered fan PWM splitter/hub devices.

You might be better off spreading your six Vardar fans into two groups of three fans each. It seems to be easier on the motherboard.
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

Korth wrote:
Been looking for self-powered fan PWM splitter/hub devices

Hello

That would be the Swiftech 8-way PWM splitter. Inexpensive and works well.

Korth wrote:
I have 6 NF-A14 industrial on my top 420mm rad, 12V 0.18A each at full spin.
All six fans together would pull 1.08A 12.96W, and the RVE should be able to easily power them across two 1A/12W PWM outputs. But I found they tended to stop and stutter and had to be spread across three mobo outputs. Been looking for self-powered fan PWM splitter/hub devices.

You might be better off spreading your six Vardar fans into two groups of three fans each. It seems to be easier on the motherboard.



Thanks for the info, good to see someone else has tried it at least.

I had ordered a cheap 6-way WPM splitter PCB with the other parts. I'll give that a try and see how it behaves. If it has issues, I'll go with just 2-3 per header. Luckily this board has more than enough headers!

Korth
Level 14
Thanx for mentioning the Swiftech product above, Praz. I didn't really know if these things existed (or what they would even be called) before.
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

Korth wrote:
Thanx for mentioning the Swiftech product above, Praz. I didn't really know if these things existed (or what they would even be called) before.

Hello

You're welcome. 🙂 I use two of those splitters connected to the R5E to control the fans on my 480 radiators.

GoNz0-
Level 10
lots of options here, self powered or not. Used one to take a PWM signal from my Asus 980 Strix with a special adapter I imported.

http://www.akasa.com.tw/update.php?tpl=product/product.list.tpl&type=Cables&type_sub=Fan%20Cable%20A...

Korth
Level 14
Just offering a little follow-up report ...

I now have two X99 systems. The R5E motherboard was moved from the watercooled system to the aircooled one, now using six NH-A14 Industrial PPC 3000PWM fans (2 on CPU cooler, 4 in chassis) which pull 0.3A/3.6W each. The R5E should be able to service 3 fans per header, but again suffers from stutter-stop issues unless I distribute them across more headers. In fact, placing two fans on any fan header other than the CPU_FAN and CPU_OPT causes issues. I don't understand why my mobo should function even worse servicing a single 0.3A fan rather than two fans which add up to 0.36A. 0.3A is fairly heavy draw for a single PC fan, but well under the 1A threshold.

I'm reasonably confident the fans aren't defective (bulk lot purchase, with some fans working perfectly in other machinery), and DMM measurements on a few pieces confirm that they each pull roughly 0.3A at 3000rpm, as advertised. I'm also confident that my PSU is more than manly enough to run my system, especially when components are removed to isolate and troubleshoot issues.

Are the published Asus R5E specs (1A/12W per fan header) incorrect? Or are their thresholds expected to fluctuate in a fully-loaded system? Or is my R5E a bit of a dud? I know electronics well and expect a little variance, but <30% actual functionality seems wrong.
"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]