Running a power supply with no fan

[Soybomb]

I think I want to run a powersupply with no fan. Think I can get away with it. Just how much heat tolerance is there in there? I'd plan on replacing the heatsinks with larger ones, but I'm not sure if thats more work than its worth or not. Anyway just checking to see if someone has already done this before or has any recommendations. (I do realize what happens if its not cooled sufficiently inside btw )

btw: I want to use a linux box as my router in my apartment and its annoyingly loud at night when I'm trying to sleep. A different fan is too easy

 

[jamarno]

I believe that most people worry too much about cooling, but here you
need the fan because even the largest heatsinks that can fit in a power
supply are far too small to provide enough cooling by convection alone.

Another major concern is high voltage risk because some of the transistors
have hundreds of volts on their exposed metal tab that mounts on the heatsink
(with some packages this tab is covered on top but exposed where it faces
the heatsink). Other transistors and diodes work at lower voltage but still
have exposed voltage and so must be electrically insulated from one another
or they'll be destroyed in an instant. Sometimes the transistors and diodes
aren't electrically isolated from their heatsinks but instead a separate heatsink
is used for each component, and that means the heatsink can be electrically
live.

I would much rather get a much larger fan that turns slower and runs quieter.
But even a slower fan of the same diameter and lower air flow capacity is much,
much better than no fan at all.

 

[Killbat]

Heh, I would think you could get away with no fan if the power supply is rated high, and the system consumes VERY little power. (i.e. you run only a 486 board with two NICs and a hard drive that spins down after bootup, which is all you'd need for a *nix router)
A classic trick to quiet it down without spending any money is to go into the supply and move the fan from the +12v line to +5v. 5 volts is enough for most brushless fans to run, but at a lower speed. Again, this is only safe if the supply is overrated for the job, but it's better than no fan. I have a home-hacked MP3 player that runs a K6-2 300 underclocked to 166 (K6's are fantastic, very low power requirements and heat), a 3.5" HDD, a CDROM, and a small LCD panel. The supply is, I think, 230W. I have the fan switched over to the +5v line to keep it quiet, and it runs reliably cool.

 

[blahblah99]

Sure you can run a power supply with no fan if you run a slow processor. I ran a pentium 166mmx with a 250W ps no fan on it inside a cabinet with very little air circulation. I'm not sure if it'll work with faster processors though. SInce your running a router, you don't need anything faster than a p133?

 

[Evadman]

I agree with everything said so far. Running with no fan, you will have to have a serously over-rated PWS. Be careful, those capacitors tend to explode if they are not saftey capped

 

[Mday]

um, no you cannot get away with running a powersupply with no fan. the thermal conditions would wreak havoc on the output voltages. you will get random crashes.

splice a resistor to the fan lead and lower the voltage going to the fan that way.

 

[CTho9305]

<< um, no you cannot get away with running a powersupply with no fan. the thermal conditions would wreak havoc on the output voltages. you will get random crashes.

splice a resistor to the fan lead and lower the voltage going to the fan that way. >>



agreed. even the coolest-running PSUs i've played with always get hot when you stop the fan. Another solution would be a larger (92mm, 120mm) fan used alone to cool the whole system (duct a little to the power supply, some to the CPU, if needed).

 

[crypticlogin]

This guy has a well-documented page for his quiet PC that uses a custom, fanless PSU. It's certainly no Athlon spec'ed PSU but if your machine is only doing routing activities, you can probably make do with just a K6 or P2 box. The guy also mentions that the PSU came at a premium so unless cost doesn't matter to and the K6/P2 would work well, fanless computer PSUs do exist.

As for modding your own PSU by shoving in larger heatsinks... I wouldn't recommend it. Even if you have awesome convection to dissipate heat from the components, you still have to get rid of the heat from inside the PSU enclosure and that's what the fan is primarily for. But hey, this shouldn't stop you since half the threads that exist in this forum have to do with non-recommended procedures!

 

[Factor5]

I've been runing my linux router for over 6 months with no crashes, its a 486 100MHz, hdd running all the time, it stays cold, works fine..... off a 100W psu, if it goes, it goes, but who caes, its quiet, i think, if you have nothing to lose, give it a try, mebbe try taking the cover off the psu.

 

[MadAd]

5v isnt always enough to get above the starting power, if it refuses to spin, or you hear a slight uneven grinding noise at 5v, then its having problems and use the 7v trick instead.

Alternativly you could try an enermax, kill one of the 2 fans, and fiddle with the thermistor mount to get the remaining fan to min rpm at idle, and exhausting more when ur above ur idle temps.

Or see the Zalman, reputed to be QUIETER than the enermax whisper, but ive not had one to personally compare - all the reviews and comments claim its quieter than the EW, infact (by reports) its the quietest one out there?

http://www.zalmantech.com/ST300BLP.html

 

[MadAd]

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