12V PC fan question

[manchild]

I've read on few places that when you replace smaller fan with bigger one it can be silenced even more by connecting it on 5V instead of 12V. I know that it works perfectly cooling-wise since big fans push greater amount of air even on 5V but what I'm not sure is the basic safety of motherboard and/or power supply unit.

If I'm not mistaken, when electric motor designed for higher voltage is connected to lower voltage it causes overheating and everything that follows it (Like running the gasoline engine on poor mixture). Am I right or not?

I know that 12V fan connected to 5V will work but for how long is what scares me.

So, I'd like to hear from electricians on this forum is such 12V to 5V conversion 100% safe or does it contain certain level of risk and uncertainty? Thanks in advance!

*I'd like to connect two 80mm 12V fans to 5V to silence PC.

[Saribro]

The only problems I've seen mentioned about connecting 12V fans to 5V is that some models can't start that low, the easy solution to that is using 7V (connecting over 12V and 5V instead of 5V and GND). Most new fans are built with thermal control in mind, so they do work fine over a pretty wide range.

There's some useful info here: http://www.silentpcreview.com/article6-page1.html
It mentions PSU-protection in the 7V case and such.

[manchild]

Thanks! That was a very useful article. I'll skip 7V experiment and settle with 5V and switch which I already have. If it can start at 5V ok, if not I'll leave it at 12V.

[Carlos]

Manchild - This program might be useful after your mods to monitor fan speed, voltage and temperatures.

http://www.almico.com/speedfan.php

[manchild]

Thanks Carlos. I'm already using it for a year or two.

[Belatti]

If you use 5V you should mount shark fins and chimneys in both gabinet sides to help cooling. That may cause turbulence in undesired places so it would be better to add sidepods with vortex generators to let air run smooth arround the mouse, keyboard and monitor. With all that you´ll get a good performance from your PC!

BTW, remember to use helmet, seatbelt and HANS (Hand Arthritis-prevention New System):