It occurred to me that a power supply claiming to supply, say, 400 or 500 Watts "must" (should!) have some pretty good heat sinking. So if one were to purchase such a PSU, and put it in a very modest system (drawing 100-200 Watts, say), then could one run it fanless do you think?

Has anyone looked into this?

I currently have the Zalman 300 PSU and it's pretty quiet, but not quiet enough. I'm planning to replace fans on it. So this is just an alternate line of thought!

It makes sense to me. I'm not sure if you'll be able to run it fanless, but a higher rated PSU should be able to transfer more heat to the air passively than a smaller one. Higher end PSU also tend to have higher quality components in general.

Most systems even fairly "high powered" ones draw way less than 200 watts. For example my XP 1800 two disk drive system just breaks the 100 watt mark at idle (with idle cooling software running) and peaks out at about 150 watts fully loaded. I am almost certain that most 400 to 500 watt PSUs designed to be fan cooled would eventually go up in smoke without fan(s) if they were powering a 100 to 150 watt system like mine. The real question here is how long would it take before you let the smoke out. The highest quality ones might work for some time (weeks, months - maybe if your lucky) before failing but most would fail at some point.

Also remember that most of these units are about 70% efficient. So at 100 watts out that means a little over 30 watts of heat needs to be dissipated from the PSU. Without a fan or an external heat sink where is that heat going to go?

In order to do what you are proposing you would have to build a system that needs way less than 100 watts to even have a fair chance of having this work.

If you want a fanless PSU why don't you just buy one that is designed to run fanless?

Good points. I was really just curious. "Fanless" was perhaps extreme, though - I would use a very slow fan, probably.

I'm working on silencing my Zalman 300, which is already pretty quiet, with better quality fans and reduced voltage - but still running.

As for actual 'fanless' models (designed that way), the ones I've seen are non-standard form-factor, and/or have buzzing associated with them. Maybe I'm getting behind with the product announcements, but I haven't seen anything that 'fits' even closely in the case and is regarded as very good. Did I miss one? Thanks, Chris