BleepingComputer.com: New System Fan Headers

Hello, I'm building off a ASUS Crosshair III. In the owners document, it states that the fan connectors support cooling fans of ;
350 mA-2000 mA ( 24 W max. ) or a total of 1 A-7A (84 W max.) at 12V.

I have 8 mobo fan headers(all PWM) (including PSU & CPU fan header ). The Mobo is a 24 pin main and 8 pin ATX.

Given the stated support specs, I added all current fan Amps together, and I'm still unsure if the Mobo is able to carry the load.

Here is a list of installed fans;
Amp. input W. (all fans 12V)
Front 120mm - .30 1.8 PWM (4pin)
Back 120 " - .35 4.2 (3pin) will run 100% for now. Have 2spd controller.
side 80 " - .15 1.8 PWM
side 80 " - .15 1.8
side 80 " - .25 ? (not found)
CPU hs 92 " - .25 ? ( " )

I'm a new builder, and don't have alot of knowledge of computations related to this total draw.
My simple math results, related to Amps = 1.36 approx. This seems to fall below 7 A max. IDK. AMPs(1.36)X Volts(12.)= 16.32 Watts ? is this correct?
I found input W for only 4 fans so I'm unsure of total.

Will this fan load be within spec, for all fans to be connected on board?
Could you link me to a good tech artical or tutorial related to the subject?

Thanks, Don

This post has been edited by PCwarrior: 19 December 2009 - 03:17 PM

I can't give specifics, just general guidlines I use. < Opinions are like a**holes, everybody has one so..........................

The only time you connect a fan to a motherboard header is if you need to control the fan via software (CPU fan etc or need some sort of software fan monitoring). Regular case fans that are either run full blast, or on a fan controller, should be hooked up to a spare molex.

The reason I go this route is because I got burned (well the motherboard got burned) many years ago running a fan that melted a fan header. I also ran into situations where some fans are electrically "noisy" and feed back to the power/ground planes on the mobo. I had one system cause me nightmares with stability problems, and after going through the troubleshooting, one of the case fans was responsible for causing the problem. Do this for a living, and you eventually get around to the oddball stuff.

That being said, your motherboard can likely supply sufficient power for all those fans without a problem. Your math seems right on.

Comparing the wire ga. size to the solder trace on a motherboard, I'll pick wire any day

This post has been edited by garmanma: 19 December 2009 - 09:26 PM

Thanks for the heads up. I did alot of work getting things laid out in the planning stages, and all seams to have payed off for now . I'll look into a fan controller soon. To switch some fans off the board. All is real sweet now though. All fans controlled and just the smoothest sounding thing.
For sure thanks, for the incite and mentoring.

should work, if its to much wattage you can always hook some of the fans up to the molex connectors on the PSU to even the load out, the 12v rails normally have plenty of ummpf.