Dust, air pressure

keyser · 22 Oct 2008 at 13:45

My rear case fan (an Amber 120mm) just died from 3 years of dust. I just hope the 120mm fan inside my Seasonic PSU lasts another 12 months, it probably will because it only went round about half the speed of case fan, so half the dust

I've been toying with getting an Antec Solo case, that has 2x 92mm front fans with filters.

Having fans that blow air out of the case will compete with each other, because of the negative air pressure they create, any holes in the case will want to suck air (+dust) in, including via the PSU, which has a low RPM fan inside. I guess what I'd like to know is, does the speed of the fan inside a PSU increase with power usage or temp? At least with front fans they work with low RPM fans.

Anyway, from a dust point of view I'm pro positive air pressure

Skidilliplop · 22 Oct 2008 at 13:53

yes, most newer PSUs have a thermally controlled fan. As for links with RPM and dust buildup.... doesn't really work like that. Just Keep the case clean as best you can. If dust is a major problem you can create a positive pressure in the case but this won't be as good for cooling.

keyser · 22 Oct 2008 at 14:11

Skidilliplop said:
yes, most newer PSUs have a thermally controlled fan.

ok thanks

Skidilliplop said:
As for links with RPM and dust buildup.... doesn't really work like that. Just Keep the case clean as best you can.

Yeah it does. More air through the case means more dust through the case. I admit I only clean my case when there's an issue with my PC though.

Skidilliplop said:
If dust is a major problem you can create a positive pressure in the case but this won't be as good for cooling.

I don't see how: if the fans are at the same speed, it'll be the same air flow. Having air filters will restrict air flow though. Also many cases don't have room for more than 1 fan at the front.

Nitristion · 22 Oct 2008 at 14:43

Yeah, like Skidilliplop said, most of the newer PSU's have thermally controlled throttle fans- the hotter it gets, the faster the fan is told to spin. It should be logical to assume that if you are sucking more air in, you will be sucking more dust in also.

I've always tried to keep good airflow in my rigs, and as such have had very few dust problems. I try to have equal intake and outtake fans (one intake, and one outtake, or two intake and two outtakes.), this way I have an equalized pressure- good for cooling, and the least amount of extra stress on the fans.

Skidilliplop · 22 Oct 2008 at 15:47

Nitristion said:
Yeah, like Skidilliplop said, most of the newer PSU's have thermally controlled throttle fans- the hotter it gets, the faster the fan is told to spin. It should be logical to assume that if you are sucking more air in, you will be sucking more dust in also.

I've always tried to keep good airflow in my rigs, and as such have had very few dust problems. I try to have equal intake and outtake fans (one intake, and one outtake, or two intake and two outtakes.), this way I have an equalized pressure- good for cooling, and the least amount of extra stress on the fans.

Indeed cooling is all about rate of Exchange. You want to replace the air in the case as many times per minute as you can thus getting the hot air out and Bringing cold air in. Ideally you want to do this Push me Pull you style so the air moves through the case at a minimal negative pressure. Moving air always causes a slight reduction in pressure but ideally keep it to a minimum.

Usually for bog standard systems one fan creating negative pressure is enough but at higher exchange rates the volumes are much higher thus you tend to get dust problems. I'd recommend filters at the front and slightly faster fan speed front than back to counter the additional extraction from the PSU. so like 1000-1200 RPM front 800 RPM back + PSU.