pulling 24v from my pc...

[GrayTap]

ok I know I can get 24vdc from my power supply...

I have two 24v 6w 120mm x 30mm fans that simply rock!!! they push a $#!^ load of cool air and are quiet to boot!!!

now to get 24v dc to run them with a standard pc setup is easy! all the yellow wires to all molex connectors are +12v dc this with the normal black grounds don't offer enough power to run one of these fans at full speed. the 24 volts is archived by connecting the black wire from the fan to the purple -12vdc wire on the ATX connection to the mother board!

so making it neat I'm getting an ATX extension cable poping out the two pins I need and soldering the appropriate wires to the extension pins and vuala nice and neat.

here is my question...

the Voltage Tolerances listed below have me asking will the two fans pull to much power and drop the motherboard voltage below the min. requirements.

Table 7: Voltage Tolerances
Parameter Range Min. Nom. Max. Unit
+12 VDC ± 5 % +11.40 +12.00 +12.60 Volts
+ 5 VDC ± 5 % +4.75 +5.00 +5.25 Volts
+3.3 VDC ± 5 % +3.14 +3.30 +3.47 Volts
-12 VDC ± 10 % -10.80 -12.00 -13.20 Volts
+ 5 VSB ± 5 % +4.75 +5.00 +5.25 Volts

I don't know how to figure out if a fan rated at 24v 6w will drop +12 VDC below +11.40v and -12 VDC below -10.80v

does anyone here have an idea if this will work or not!?

Thanks in advance.

[Solid Snake]

Don't do it. You won't pull down your +12v, but you'll pull up your -12v. It's a very low current line used for the serial port.

[JPMiller]

What your doing is simple overvolting...
This is NOT something you want to do using motherboard connections...
I dont ever even use the motherboard connectors for ANY fans period!
The less current drawn through the board the better...
Simply do it connected to molex from the PSU directly...

---NVM---misread...

[DanU]

Will it work? Most likely yes, but as Solid Snake mentioned, it might screw up your serial ports. The -12V line has very little power available.

Why don't you just get a 12V version of the same fan? Voltage is irrelevant. What matters is POWER. All other things being equal, a 12V, 6W fan will have the same airflow as a 24V, 6W fan.