PSU fan won't start now I swapped fans

PSUs: The source of DC power for all components in the PC & often a big noise source.

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williamn6133
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PSU fan won't start now I swapped fans

Post by williamn6133 » Mon Dec 05, 2011 4:45 am

Help! I swapped the fan on my Seasonic SS330-GB (which, by the way, is not flipping silent out of the box)

The fan I put in there is a black Skythe without much branding. DC 12v 0.18A. It won't start spinning, because the PSU doesn't give it enough amps (?) to start, but if I give it a flick with my finger, then the fan spins happily.

I have 2 questions. Hope someone can be kind enough to help me out.

1) What kind of fan (amp, DC, Watt, ratings?) do I need to put in my Seasonic PSU, given that the PSU runs whatever fan it is fitted with at "low speed".

2) Any 2 pin 12cm fans I can buy!?

Thank you

PS. I used to know quite a lot about all this stuff (look at my signature) but my brain is practically disabled by comparison these days. Please be patient ! Thank you!

Vicotnik
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Re: PSU fan won't start now I swapped fans

Post by Vicotnik » Mon Dec 05, 2011 5:13 am

If you plan to use the PSU internal fan control, then you need to make sure that the fan you replace it with match the stock one. If it doesn't I would recommend that you power the fan by some other means, perhaps control it via a motherboard connector or use a Fanmate. Sometimes I hotwire the fan to 7v or 5v inside the PSU, if I feel that that will be both quiet and cool enough. Fan control can be useful sometimes though.

I cannot recommend a fan, as I know little about which are known to start at low voltage. Some other member can help with that I'm sure.

williamn6133
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Re: PSU fan won't start now I swapped fans

Post by williamn6133 » Mon Dec 05, 2011 7:03 am

Vicotnik wrote:If you plan to use the PSU internal fan control, then you need to make sure that the fan you replace it with match the stock one. If it doesn't I would recommend that you power the fan by some other means, perhaps control it via a motherboard connector
Thanks!!!!! :D

I don't care about fan control, since the fan I repaced it with it way more efficient. So I'll plug it into something else to power it. Can't believe I didn't think of that. But how do you get the fan cable out of the PSU? The PSU case is very tight fitting.

Vicotnik
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Re: PSU fan won't start now I swapped fans

Post by Vicotnik » Mon Dec 05, 2011 8:08 am

I drill a hole myself if I have to, but usually there's a vent hole somewhere. Cutting the cables are probably required but a little work with a soldering iron and some heat shrink tubing fixes that. If the cable length need to be modified you need to cut it anyway. Or get the wires out of the plug using a needle or something, but don't mix them up when you put them back. Make sure the cable is secured and somewhat "pull-resilient" and shroud it in a cable sock if you want it to look just right. ;)

But it is not Zen enough until you forget to plug it in, remember that.

edh
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Re: PSU fan won't start now I swapped fans

Post by edh » Mon Dec 05, 2011 3:02 pm

What are the specs of the existing fan? If you have model numbers of each fan this may help a lot to work out what it is rated at and what it should be running at.

This is a starting voltage issue. The fan you have installed is probably a lower RPM rated unit and therefore has a higher starting voltage than the higher RPM rated (more current) existing model. I think you need to go for something a little higher RPM rated to make this work correctly.

Although it might sound a little 'brave', if you leave the fan for a little time without it starting it may then start spinning once the temperature in the PSU is high enough that the fan control kicks in and raises the voltage. A Seasonic PSU you would expect to have good enough thermal control and built in overheat protection that this won't be an issue but that is only in theory.

I personally wouldn't go for the motherboard header power setup as some PSUs do not start up without a fan connected and there is the potential for loss of connection much easier. Keeping the cable inside the PSU also makes things much tidier and gives you proper speed control of the fan.

Klusu
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Re: PSU fan won't start now I swapped fans

Post by Klusu » Tue Dec 06, 2011 12:59 am

williamn6133 wrote:It won't start spinning
The unit will get hotter, the fan will start. Don't worry. Your system does not draw 500W, any fan will do. If you wanted to take max power from the PSU, then the fan should be similar to the original (rpm, amps).

ntavlas
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Re: PSU fan won't start now I swapped fans

Post by ntavlas » Tue Dec 06, 2011 3:16 am

I think it`s a bit risky to leave it as it is. While the main components are probably ok (otherwise the psu would increase the voltage fed to the fan) others might overheat. There`s simply no way of knowing for sure since there are usually no sensors on capacitors, tranformers etc. I'd rather not take the gamble.

As for which fan to use: faster fans have usually lower starting voltages. You will see this pattern emerging if you look at fan reviews over here or at xbit labs. Another thing to consider is that starting voltage is likely to increase as the fan ages so a fan that is barely able to start now might not do so in the future.

In practice, I`ve had good results using the skythe sflex @ 1600 rpm though 2000 rpm would be even better IMO. Still, I have used this fan in many PSUs and it has been able to start reliably every time, even after 6 years of use.

skeeder
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Re: PSU fan won't start now I swapped fans

Post by skeeder » Tue Dec 13, 2011 9:56 am

when I did this with an old antec I wired the fan to the mobo and used AMD's Cool and Quiet to silence the MOBO Fans...so when the CPU started getting warm so would my psu fan...

Klusu
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Re: PSU fan won't start now I swapped fans

Post by Klusu » Tue Dec 13, 2011 1:33 pm

It's better not to take the task away from the PSU. The PSU knows, how much airflow it needs.

ntavlas
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Re: PSU fan won't start now I swapped fans

Post by ntavlas » Tue Dec 13, 2011 1:41 pm

It's better not to take the task away from the PSU. The PSU knows, how much airflow it needs.
Agreed. That`s especially true if the gpu is a significant part of the load, in which case the temperature of the cpu does not necesarilly correlate to that of the power supply.

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