Can I run computer fans at greater than "max amperage"?

[shelburn61]

I ran a 80mm computer fan for over a year on a 12V transformer with a 800mA rating. I assume this nearly 8 times the "max current" rating for the fan since all the 80mm fans I see for sale now are rated at ~.1A. How was this possible?

I know nothing about electricity. Can someone give me a brief explanation of volts, amps, watts as they relate to cooling fans and transformers?

 

[prugs]

If the transformer is rated 12 volts at .8 amps, you could run 8 of those fans. Provided the fans are rated at 12 volts & .1 amps.

 

[shelburn61]

so there is no problem running a fan on a transformer with a higher rated amperage?

If so why does the 12v 300mA transformer I have run the same fan at a much slower speed?

 

[Donw]

The fans are only going to draw what they draw. You could use a 10a supply and their still only going to draw .1a

Don

 

[sunkool]

same thing I was thinking. Mine is a 1000ma 12v. I guess I could run 10? Not that I need to, just don't want to burn out the fan.

 

[shelburn61]

<a href=showthread.php?s=&postid=9120028#post9120028 target=_blank>Originally posted</a> by shelburn61
so why does the 12v 300mA transformer I have run the same fan at a much slower speed?

 

[prugs]

<a href=showthread.php?s=&postid=9120077#post9120077 target=_blank>Originally posted</a> by shelburn61

Could be a drop in voltage if the wire is to small & to long. A drop in voltage is going to demand more amperage, maybe more than .3 amps. Or the two transformers have different voltage outputs (this is what I suspect). No way to tell without a VOM.

 

[Siberia]

<a href=showthread.php?s=&postid=9120028#post9120028 target=_blank>Originally posted</a> by shelburn61
so there is no problem running a fan on a transformer with a higher rated amperage?

If so why does the 12v 300mA transformer I have run the same fan at a much slower speed?

Possibly there is a problem with the voltage regulator or, as someone else mentioned, a voltage drop (Probably caused by the voltage regulator). Indeed, a VOM would be required to properly analyze and assess the state of your power supply and your fan. Fans will fail too.

HTH

 

[BeanAnimal]

the "voltage rating" of the PSU is nominal and usually only meaningfull whn ethe PSU is under moderate load. With no load (or a light load) the PSU may float at a voltage somewhat higher than the label rating. This all depends on the type of PSU, regulator circuitry etc. So 2 different brands of 12V 1A PSUs may float at a different voltage.

Bean

 

[JOSEPHLB]

<a href=showthread.php?s=&postid=9120045#post9120045 target=_blank>Originally posted</a> by Donw
The fans are only going to draw what they draw. You could use a 10a supply and their still only going to draw .1a

Don

Right on the money.



Think of current as a river. This "river" has to carry that 12v to the source. The 12v never changes; its a fixed amount. Voltage is also known as "potential".

Good info to know (applies to DC circuits, simple series circuits):

Volts / Resistance = Current
Volts / Current = Resistance
Wattage = Voltage x Current..

 

[BeanAnimal]

I guess I need to use the spell checker more often.

Meaningful when the...

 

[jtemple42000]

As mentioned above those outputs on the transformer are simply what the transformer is able to supply. The fan will only use what it needs and the tranformer will only supply what is drawn. The current of the transformer isn't really a big deal unless its not enough. Now on the other hand, you wouldn't want to plug a 12volt fan into a 24volt transformer. If it didn't burn the fan out right away, it would run the fan, really fans, but not for long.

 

[BeanAnimal]

It should also be mentioned that you should not push the power supply to its maximum rating. In other words if it is labled at 500ma, then you do not want to add 500ma worth of fans to it. 400ma or so would be a better maximum load. These things are built cheaply and live a short life if overloaded. Just leave yourself some headroom. I would only load the PSU to 50%-75% of it's label rating.

Bean