Question for those of you running 24V fans

Have any of you had problems with your fans dying due to running them on low voltage? I had one of my watercooling rigs using a Comair Rotron and it was working fine for a couple weeks. Then one day I came home and the system had powered off and the fan wasn't working. Nothing I could do would revive it.

Since then I bought two more (Majors this time) and I am going to be running them off two different laptop power supplies. One is the quiet setting using a 24V power supply with the fans run in parallel and the other is for the power setting using a 19V power supply. They just have too much of a whine at 24V for my liking and I think I get 90% of the power at 19V anyway.

So is this something I am going to have to deal with in the future? I really don't want to have my cooling system dying due to funky voltages. Any thoughts?

nobody has any advice for me? I know you are using these fans. Help a brotha out!

I'm rather interested myself. I'm running Comair/Rotron 24v Patriots in 12v mode. Hope I'm not killing them.

Any electrical specialists have comments?

Comair fans should be more than happy at 12v. It's the crappier brands that you have to worry about. I doubt it was the undervolting that killed your fans. It was more likely... just their time. Death came early for them.

i kind of had the same thing with my torin blower, but it wasn't dying...
My guess - low voltage means less torque. After some time, dust and the lack of lubrication will start to affect the fan until it slows down or stops. my fan started buzzing and wouldn't spin at 7v, after getting some 3n1 oil (sae 20 i believe) the buzzing stopped, it spinned faster, and worked at 7v.
DC fans don't die from lower voltages, only AC fans do.

Well... AC fans 'can' die from lower voltage =p

vonkaar said:

Well... AC fans 'can' die from lower voltage =p

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yea, remember, u were the one that told me
and the 3n1 oil as well.
all credit goes to vonkaar!

I AM AMAZING

oh yeah... I forget... although, I'm still amazing.

What is this 3in1? sounds like a good drink.

Will air tool oil do the same?

Stay within the ratings in regards to voltage and you should be fine.

Remember, if you drop the voltage from 24 down to 12, the current doubles. = excess heat the motor may not be able to handle.

what if I am running them in series? I plan to use a 24V power supply with 1.5A rating with two of the 24V fans in series. When using them in this configuration the other day, the fans worked great and I noticed the power supply was a bit warm, but not hot. Should I be worried?

UberBlue said:

Stay within the ratings in regards to voltage and you should be fine.

Remember, if you drop the voltage from 24 down to 12, the current doubles. = excess heat the motor may not be able to handle.

Click to expand...

Sorry to correct you: if you drop the voltage from 24 down to 12, the current will HALVE...

I (amp) = U (volts) x R (ohms)
If U halves, I halves, R being a constant...

I know DC fans are generally not "real" resistive loads (they are swiched brushless motors), but Ohm's law still applies to them...

Most 24V DC fans are capable to run at voltages as low as 10 to 12V (see the manufacturer's datasheet), they will even run at lower voltages but then be aware that they maybe are not able to start at that lower voltage (stall voltage is lower than minimum startup voltage).

Lower voltages than the indicated average voltage will not kill a fan, higher voltages will (by drastically decreasing MTBF of the fan).

AC fans are a different issue, they are generally synchrone motors, their RPM is directly proportional to mains frequency - 50 or 60Hz, as also do AC mag drive water pumps. The only way to change their speed is by varying the frequency of the applied AC voltage.
This is why running them through an AC dimmer or a potentiometer doesn't work. If you try you will observe that at a certain point the AC fan will stall without even having changed in speed...

CD

Posidon42 said:

what if I am running them in series? I plan to use a 24V power supply with 1.5A rating with two of the 24V fans in series. When using them in this configuration the other day, the fans worked great and I noticed the power supply was a bit warm, but not hot. Should I be worried?

Click to expand...

Assuming both fans are identical and assuming their current draw at 12V does not exceed the 1.5A rating of your power supply it will be just fine. In series, both fans will receive half of the applied 24V voltage =12V.
It's normal for linear power supplies to produce heat (that's the way they work...).

CD

Ok, I will continue on with my current approach as long as it won't kill these fans. I would still like to figure out what happened to the other one that died, but I guess that is what I get for buying stuff from a surplus shop