120 mm fan bad for mobos?

Project · Post by **Project** » Sat Jul 10, 2004 1:26 pm

is it bad to plug in a 120mm fan thats 3 pinned into a motherboard. I read that u can over load the circuit or something

dukla2000 · Post by **dukla2000** » Sat Jul 10, 2004 3:32 pm

Only if the fan load requirement exceeds the mobo header ability. As all fans vary and all mobos, you need to check the specs of both of yours - typically measured in mA (milli-Amps).

Project · Post by **Project** » Sat Jul 10, 2004 4:07 pm

mmm i tried looking at the manual and box, no can do, should i email the manufacturer

pandamonium54 · Post by **pandamonium54** » Sat Jul 10, 2004 9:48 pm

I'd avoid it if I were you. 120mm fans generally pull a good amount of power. A good rule of thumb for fan headers is to power anything >=80mm separately.

The only real risk, AFAIK, is that you would burn out the power header on the motherboard. It's not really that big a deal, but you'd end up powering your fan via PSU adapters anyway...

dukla2000 · Post by **dukla2000** » Sun Jul 11, 2004 10:43 am

Project wrote:mmm i tried looking at the manual and box, no can do, should i email the manufacturer

If it is not in the manual under the section that describes the (3-pin) fan headers then your only option is to try the manufacturer. For reference my A7V333 is 350mA = 4.2W: a Papst 4412FGL is 1.3W (55cfm) so no problem, but a Dynaeon DF1212BB is 4.6W (87cfm) and would be a problem.

But as per pandamonium54, in case of doubt it is better to avoid problems and use a spare molex. Melting the header is one thing, any collateral damage can really ruin your day!

Skylined · Post by **Skylined** » Mon Jul 12, 2004 9:45 am

I wouldn't plug a 120mm fan to the mobo.

Take off from the plastic connector the fan's ground and positive pins, leave the RPM sensor inside that plastic connector.
Plug that connector to the motherboard so that you'll have RPM sensing.
Then plug the fan directly to the PSU (yellow and black cable), use a molex, solder it, whatever you want, but plug it directly to the PSU.

I have 0 fans running off my mobo, all of them running directly from PSU.

loren_brothers · Post by **loren_brothers** » Mon Jul 12, 2004 10:59 am

dukla2000 wrote:Only if the fan load requirement exceeds the mobo header ability. As all fans vary and all mobos, you need to check the specs of both of yours - typically measured in mA (milli-Amps).

The above is the only thing that really matters. Anything else is really just personal preferences. Unless you are running a dino-MB or a dino-fan it is highly doubtful that problems will occur. MOST fans that have a 3-pin connector are spec'ed for just that usage: running off the MB!

Of course if you don't want RPM monitoring: don't buy a fan with that option (save money) or just hook it direct with the 4-pin. Different strokes for diffent folks!

But as a general rule......absolutely no problems will caused to the MB by running 2 normal low RPM 120mm fans off it. I do it...at the full 12V "jet airplane" speed.

(1200 and 1800 RPMs)

silvervarg · Post by **silvervarg** » Tue Jul 13, 2004 1:59 am

It is common that high current fans are sold with 4 pin headers only. So a fan with a 3 pin header is likely to draw little current, so connecting to the motherboard is usually not a problem. Checking the specification is of course the best things to do.

As a rule of thumb the moderboard headers can usually source about 300-400mA. On quite a lot of motherboards the CPU-fan header can source a bit more, usually in the 600mA range.

Mr Flibble · Post by **Mr Flibble** » Sat Jul 17, 2004 4:48 am

silvervarg wrote:It is common that high current fans are sold with 4 pin headers only. So a fan with a 3 pin header is likely to draw little current, so connecting to the motherboard is usually not a problem. Checking the specification is of course the best things to do.

Unfortunately it's not always the case - I once blew the headers on my old A7V-266 using a 60mm Delta

(long ago relegated to the bin)... Similarly 80mm Deltas often come with 3 pin connectors. I think a lot of this is to connect to fan controllers. Mind you, this shouldn't be a problem for most SPCR readers