Accidentally left my radiator fan off...

I turned off my radiator fan this morning to test the effect of having no fan, and accidentally left it off while I went to church for about two hours. Came back...and my temp was only up to 34C in 22C ambient. Turned the fan back on to 7v, and I only dropped down a couple degrees. I think there was still air going through the rad though - I could feel it blowing out the back due to positive air pressure in the case. Just an interesting discovery.

BTW - I'm not overclocked right now, just at ~2160mhz w/ 1.525v. I'm sure that with more vcore and my usual overclock the effect would be quite different.

If you use your rad fans as intake into the case then you probably had negative pressure sucking in air. It's actually pretty powerful, since pressure like to adjust itself. Negative pressure causes a whole lot of dust though....

Lol.. if your rad fan adds any noticable noise I would just take that sucker off...

Yeah...I'll have to try testing it again at higher temps/voltages. I usually have it at 7v though, and since it's a nice 120mm Panaflo I can't hear it over the rest of the system.

My rad fan is actually used as exhaust at the top back of the case, so it is indeed positive pressure.

What pump have you got? For a setup like that to work you need one that won't dump a lot of heat into the water.

The main reason for that is probably that you have some other fans blowing in or out right? The negetive or positive pressure has to find a place to go or come from so it goes through the radiator. I wanted to do this at one time, use the computer case as a shroud. The only bad part is that the fans might fight against each other and cause even more noise, but if they dont it would work pretty well.

Jon

eobard - actually, I'm using a Danner Mag 3 - not the most efficient pump in terms of heat output. I think they main reason it worked as well as it did is because my 1700+ was only running at 1.525v. Those things run pretty cool. It'll be interesting to play around with some higher voltages/overclocks during the next few days when I find time. Unfortunately, applying to Stanford is eating my time.

JFettig - yes, I believe the positive case pressure made most of the difference. Like I said, I could feel air being pushed out of the rad even with the fan off...even to the extent of me bending over and checking to see if the blades were spinning. Using a Chieftech-style full tower case, I have 5x80mm intakes (Panaflo L1A's) and a generic 120mm fan @ 7v also on intake. The 80mm's are in the front three intakes and also blowing in from the back two 80mm slots, while the 120mm intake is over my video card. My only exhaust is a 92mm fan at about 5v (blowhole on top) and the radiator at the top rear of the case. I also have an Antec 400w PSU with an L1A and some of the sides cut out and replaced with very unrestrictive wire mesh. There's obviously a good deal of pressure coming in.

I've been thinking about adding another radiator to the front bottom of the case. Once I find what kind of results I achieve at higher temps and voltages, perhaps I will no longer need a fan and shroud at the top rear of the case. That would save me a good deal of money.

I unplugged my heatercore fan once to experiment a bit, it's external and uneffected by case fans. I saw 37C idling on the net, and 39C loaded. Mine's in a cool location in the basement though. My pump is in a reservior on the wall next to my desk, so all of it's heat is in the water system as well.

You might even get better temps with a negative pressure system, as the cooler ambient air would be what's circulating through the 'unfanned' rad.
Just a thought.

Some Results...

I kicked my vCore up to 1.85v.

Fan at 7v - Idle (well...just normal low CPU usage stuff...word documents, etc.): 25C system temp, 39C CPU temp.

Fan off doing similiar "idle" applications: 27C system temp, 43C CPU temp.

Fan at 7v with Sandra burn-in for load temps: 26C system temp, 43C CPU temp.

Fan off at load: 29C system temp, 49C CPU temp.

Guess I'll be leaving that fan on after all...at least when I'm overclocked. FYI, I'm using a Chevette core with a 120x38mm Panaflo U1A and shroud, a Danner Mag 3, DTek Spir@l CPU block, bayres, and 1/2" ID clearflex.