Fan Header Current

MrScott · 18 Aug 2006 at 13:26

Hello all, just a quick question.

I'm just moving my PC into a new case, and have 2 60mm fans I'd like to speed control, so I'd like to run them both off the system fan header on the motherboard. My question is whether it'll damage the header / board by running 2 fans.

Each fan is rated at 0.17A at 12V, I've checked my motherboard manual (GigaByte Ga-K8NXP-9) but it doesn't say how much current you can pull from the fan headers. 0.34A isn't a lot so I'd guess it would be fine, but I was wondering if fan headers are really restricted to 1 fan.

Thanks,
Scott.

Tetras · 18 Aug 2006 at 13:29

If it was me I really wouldn't do that, a molex sure but a motherboard fan header invokes those "uh oh" vibes

Harryo · 18 Aug 2006 at 14:52

lord_scott said:
Each fan is rated at 0.17A at 12V, I've checked my motherboard manual (GigaByte Ga-K8NXP-9) but it doesn't say how much current you can pull from the fan headers. 0.34A isn't a lot so I'd guess it would be fine, but I was wondering if fan headers are really restricted to 1 fan.

Thanks,
Scott.

Hi Scott, I have the same motherboard and have just moved all my components to a new Gigabyte 3D Aurora case.

This case is fitted with two rear 120mm fans rated at 12v 0.20A each, the manual that came with the Gigabyte case recommends connecting these fans to the SYS_FAN connector on the motherboard, which I have done without any problem.

I am loathe to connect any particular fans to these motherboard fan headers unless recommended to do so by the motherboard manufacturer, as like yourself I have no idea what the power ratings of them are.

This afternoon I have just added a Zalman VF700-Cu LED VGA Cooler to my video card but the fan connection for this utilises a 4-pin Molex connector.

You can always ask Gigabyte a question regarding the fan connector:-

http://www.gigabyte.com.tw/Support/ServiceCenter.aspx

Any questions I have asked them they have usually replied to in a couple of days.

Cheers - Harryo

boosfuk · 18 Aug 2006 at 15:11

I've seen posts in the past where people have quoted motherboard documentation (for ABIT m/b) that states 3-6W max per header (I believe lower value is for Northbridge headers vs CPU/system headers for the higher). So your ~4W (as I guess you know VxA=W) is quite high. I've always run 120mm (~2-3W) fans from headers with no issues but many others (as above) say don't do it.
Of course it always depends on your motherboard/manfacturer and Gigabyte might be much lower. I've always used ABIT/ASUS, I would be less confident with others.
If in doubt run one fan with speed control and have the other running at lower volts with for example a fanmate (and 3pin to 4pin adapter) off a molex.

MrScott · 18 Aug 2006 at 15:19

Thanks a lot Harryo very useful, sounds like it should be OK then. I've just tried one of the fans on the header now and I can't seem to control the speed using SpeedFan, so I may as well run them off a molex anyway just to be safe. Thanks a lot.

Edit: Just seen your post boosfuk, I'm kinda glad they're on a molex now. Pity manufacturers don't include specs like this in mobo manuals.