Overpressure question

I trying to find out about how much overpressure there should
be in my case. If there is too much, does it do harm? This is
a general question as I have not started building my machine
yet.

BTW, I've been lurking here for awhile now and this seems like
a great place for info. The attitude is positive and I'm really
glad to have found it.

You don't want too much overpressure, as your airflow will be impeded. A slight amount is better, so you aren't drawing too much air(and dust) through drive bays, your CD and Floppy, etc. Ideally, a 120mm intake and 80mm or 92mm exhaust fans will serve you well.

Be sure to include your power supply fan in the equation as it can pull quite a bit of air out of the case on its own. In mine, I only have one (80mm) case fan blowing in, and the PS fan is the only one blowing out. Works great in my application.

I build my systems to have about 5-10% overpressure with all fans on and at 12V. But most of my fans are split to run at either 5/12V or 7/12V and I rarely run all the fans at 12V. I generaly turn on more intake fans than exaust.....

I build my systems to have about 5-10% overpressure with all fans on and at 12V. But most of my fans are split to run at either 5/12V or 7/12V and I rarely run all the fans at 12V. I generaly turn on more intake fans than exaust.....