Fan Amperage

[TopToBottom]

I am replacing my desktop 92mm cooling fan.

When I unpackaged the new fan, the sticker on it says DC 12v 0.20A and the one in my case is a 0.50A. What difference will the lower amperage make and should I use it?

 

[Scougs]

The lower current probably indicates that the newer fan will not rotate as quickly (i.e. lower rpm). This will probably result in less air movement. Whether or not you use it is up to you.

 

[Guest]

Just change it and forget about the amperage. It will be ok.

 

[The_OGS]

Hi TopToBottom,
Wow! That's a gnarly 92mm fan that's rated for 0.50A - which equals what, 6 Watts? A fan like that would be thick (thicker than regular 25mm) and spin ~7000 rpm, LoL. Silent model, heheh... 100cfm probably.
The 0.20A is more typical; 2.4W and ~50cfm. Note that this too would be relatively powerful fan, but average.
Here's a Thermaltake SilentBoost 92mm fan I have - they're great by the way, large and moves a lot of air - and it wants 0.25A.
So 0.50A is really a lot! Too much for a motherboard plug, use molex only.
I use a lot of Vantec Stealth fans. Their 92mm is 0.84W @ 1750rpm, which is only 0.07A. A 92mm fan like this is quiet but still moves good air (almost 30cfm).
A faster 80mm fan might claim more cfm, and also use more power.
These Stealth fans are really not appropriate for CPU coolers, at least not in the smaller 60mm and 80mm sizes, but big coolers with 120mm and even 92mm fans will usually work okay (and very quiet!) with the low rpm fan.
The 0.20A fan you mention should be great for CPU or casefan duty. It would be considered typical for CPU cooler and strong as a casefan.
Now I know people love to use motherboard-monitored power plugs, and it's okay! Especially modern motherboards, if your powersupply is 24-pin and you have the 4-pin squareplug (and even molex) mobo connections, no worries.
But nice older rigs with 20-pin powersupplies should always molex all their fans whenever possible, this is important. Resist the urge to monitor these fans and always bypass the mobo, with the obvious exception being the CPU fan.
That 500mA fan you mentioned is pushing the 3-pin spec on any mobo, even the most modern, however. I would definitely molex that sucker!
Perhaps the newest mobos (with 4-pin monitored CPU fan power) will happily supply a 6 Watt fan, but I doubt it. I will check it out,
Regards

 

[blunc]

Replacing your fan that is rated to used 0.5 amps of current with a fan that is rated to use 0.25 amps of current means that it takes less current from your PSU to run the fan and therefore will load the PSU less than the old fan. One thing to be concerned about is the CFM (rated airflow) of the fan, lower CFM means it will move less air and will affect your temps.

 

[TopToBottom]

Thanks for your replies.

The fan 0.50A fan came as OE with my Dell and is a 3 pin. I'm concerned more about lowering my cfm's vs. taxing the PSU. Gotta be a reason Dell went with this size because I doubt they could possibly ever think of overkill.

Desktop sits below my desk and noise is not a problem with the OE fan.

The OE body looks like a 25mm.

Would it be better to just stick with a equal replacement?

 

[TopToBottom]

I was doin' a little searchin' on this Dell case fan and found a comment on one of the forums about this high Amp fan.

"Yes, 92mm case fan which is mounted using the EAR type rubber fan mounts. It's rated at 0.56A. (damn!) It's a thermally controlled fan. But the thermistor is in the fan. No motherboard controlled fan speed. So if you plugged a standard fan in, it would run at full speed."

Sounds like I do need to replace with OE fan!

 

[Doughbuy]

I don't think you need to, you might want to google the fan manufactuer (I'm pretty sure Dell doesn't make fans) and see what the specs are. But either way, if you bought a new fan, they should perform better than Dell stock fans. You don't need a thermistor if you don't care about just running it full power all the time. I'm not sure if your mobo has a 3-pin header, so you might need to connect it via molex, but the fan should work fine.

Getting anything through the manufactuer is a pain and overpriced.

 

[The_OGS]

Ahhh yes, the Dell CPU cooler with plastic shroud that exhausts through the rear...
A replacement for that fan would be Vantec Thermoflow (which reacts to temp and regulates its own speed).
You could use the 0.20A fan, but you would have to keep an eye on the CPU cooler. Don't let it clog up with ~2 years worth of clagg, y'know?
Don't laugh - the big-amp OEM fan is over-engineered, to pull air through there no matter what...
Anyway, if you are a Home Theatre guy or in a quiet office, the 0.20A fan would be great.
If you are a hard-core gamer, the Vantec Tornado (at a constant high speed) will keep yer cool. Gamers don't care about noise, heheh.
But the automatically variable fans are good - your system starts up totally quiet, then the noise slowly builds after ~5 minutes or so...
L8R

 

[BlackHeart]

That 500mA fan you mentioned is pushing the 3-pin spec on any mobo, even the most modern, however. I would definitely molex that sucker!
Perhaps the newest mobos (with 4-pin monitored CPU fan power) will happily supply a 6 Watt fan, but I doubt it. I will check it out,
Regards

Hmm, somebody tell that to Intel.

My D945GPM motherboard is spec'd at 3 amps for the CPU fan and 1.5 amps EACH for the front and rear 3-pin fan connectors.

 

[The_OGS]

Wow - that's HUGE fan support, that's great :^)
As I said, the newest (24-pin) mobos are different, and have been significantly beefed-up in this regard... but that is certainly more than adequate!
Yours is the exception though, and I will still caution folks (most of whom have 20-pin mobo power) to keep the fan loads off the mobo if possible.
Regards

 

[RichPLS]

My Asus A8R32-MVP mobo manual states that the 4 onboard fan connectors (3-pin)support a combined max of 41.76 watts max, which is 10.44watts per fan, yet for any single fan connector should not exceed 24watts max.

 

[BlackHeart]

My Asus A8R32-MVP mobo manual states that the 4 (3-pin) fan connectors support a combined max of 41.76 watts max, which is 10.44watts per fan, yet for any single fan connector should not exceed 24watts max.

24 watts, thats 2 amps! Thats more than mine. hehe.

 

[The_OGS]

Look guys, I dunno...
Those are heavy watts there - you understand The Law, right? The Law that says Amps times Volts equals Watts...
Anyway, these crazy fans reaffirm my warning to nice older, traditional rigs from ~2003 and earlier:
These fans will exceed 500ma on CPU and ~300ma on the total of the other mobo connections, when supplying fans through the mobo. Too much!
So clearly. modern mobos have some serious modern fan support (including the whole 4-pin thing, with integrated speed control) so - it's good!
Folks love to use the fan-monitoring function as I have mentioned, and there are now several layers of fan speed controls available to you.
Regards

 

[RichPLS]

My board has four 3-pin onboard fan connectors, not 4-pin connectors.

 

[The_OGS]

Yessir, the new 4-pin mobo fan controllers are controlling the latest CPU fans only.
Regular 3-pin fans for everything else still apply (with apparently much higher power capabilities :^)
L8R

 

[BlackHeart]

Yeah, these new fans have some electronics added to them also. I do not know if any noise might be transmitted on the motherboard rail from the fan connectors even though they are supposed to be DC fans. I don't have an oscilloscope anymore so I do not have any way to look at the signals (just for grins).