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Running a 200W psu without fans.

Posted: Sun Mar 10, 2013 6:23 am
by unkletom
I'm building a HTPC with a dual core celeron ivy bridge processor. I'm guessing the whole system will take up like 50 watt on load since its also using onboard graphics.

I have the following PSU coming in soon http://www.lc-power.de/index.php?id=366&L=1

I want to run the PSU without the fan. It's only 200w I doubt it'll get hot right?

What's your thoughts on this?

Re: Running a 200W psu without fans.

Posted: Sun Mar 10, 2013 8:03 am
by edh
Welcome to SPCR!

If you look through the SPCR PSU articles there were some early experiments with running standard PSUs passive. They were generally pretty risky. A modern PSU might be more efficient but you are dealing with heat in many small components, not just the large MOSFETs which are attached to a heatsink.

What sort of case will this go in?

It seems perhaps a bit extreme unless the rest of the system has no moving parts already. Rather than going straight in and trying this with a new build I would first put the system together, listen to the noise level of individual components, measure the power consumption and then experiment with making changes. If the PSU fan is not thermally controlled and runs at 12V all of the time then you should be safe to try running the PSU fan at 7V, 5V or even 3.3V. You could also try removing the fan grill to improve airflow. These steps are not as extreme as running fully fanless and more likely to be successful.

Re: Running a 200W psu without fans.

Posted: Sun Mar 10, 2013 8:06 am
by CA_Steve
Short answer: Don't do it.

Longer answer:

The manufacturer doesn't list this PSU's efficiency and it doesn't appear to be 80 Plus rated. So, chances are, it's 80% efficient at best and they just didn't bother spending the money and time to get it 80 Plus rated. At worst, it's an old school 70% efficient supply.

50W load under what scenario? Idle? video playback? h.264 encoding? You don't mention the other system components, so it's hard to know what your true idle/load scenarios will be. If you take the components in Hardware.info's mobo roundup, the best case idle, 3DMark Vantage, and Cinebench measurements are 24W (AC), 61W, and 84W. Replace the quad with your Celeron, and it would go to roughly 24W, 55W, and 62W. If your PSU met 80% at low loads (doubtful), the internal heat is ~5W at idle to ~12.5W running Cinebench.

If your PSU is closer to 70%, this could go up to ~ 26W, 61W, and 68W. That's 7.5W to 20W of heat dissipation inside the PSU. If your mobo uses more power than the most efficient one I used here, then this could make your idle and load go up another 20-30W with commensurate heat load.

So, no, I wouldn't kill the fan. If you want quiet and SFX form factor, consider getting an 80+ Gold rated PSU.

Re: Running a 200W psu without fans.

Posted: Tue Mar 12, 2013 6:21 pm
by unkletom
How dos running a fan on a lower voltage work.
Do I cut the white and red wire and twist the red to the white one going in the circuitboard?

Would this work even if its not the best option?

Re: Running a 200W psu without fans.

Posted: Tue Mar 12, 2013 8:00 pm
by xan_user
what mobo are you (going to be) using?
unkletom wrote:How dos running a fan on a lower voltage work.
Do I cut the white and red wire and twist the red to the white one going in the circuitboard?

Would this work even if its not the best option?
http://www.silentpcreview.com/article6-page1.html


may i sugest an alternative to your choice in psu?
http://www.silentpcreview.com/article601-page1.html

Re: Running a 200W psu without fans.

Posted: Sat Mar 23, 2013 1:47 pm
by HellDiverUK
Run the fan slower by adding a resistor in the cable. Depending on the fan, about 100ohm 1W is about right. Make sure to insulate the connections, I use heat-shrink.