Bitcoin Forum

So we're starting to see single digit temperatures (to euro people thats -15c roughly) and have 2 mining PCs sitting outside. Of the video cards mining, 2 are 5870s, both have had their stock fans fail long ago. One got a shiny Zalmna VF-3000A, the other is using a "naked" reference heatsink with a 4500 RPM 80mm fan duct taped and sealed onto the exhaust end, blowing the air in reverse. The ghetto heatsink is working just fine, seeing 31C core with 1080/330 and 1.212 vcore. The shiny VF-3000A is succumbing to the cold though; the liquid inside can't stay liquid in the extreme cold is is freezing up by the aluminum fins, leaving only the copper pipes able to transfer heat. This picture can clearly show whats happening.

http://dl.dropbox.com/u/9768004/heatsink.png

Trying to think of the optimum solution here. I could try to dig out the other reference heatsink and find another fan (though 80mm's are hard to find in my house). I also have one of these http://www.thermalright.com/new_a_page/product_page/archives/nb1.html but it's made of aluminum and I lost the fan for it. Any input fellow miners?

I would be surprised if your analysis is correct. For the water in the heatpipe to freeze, it must be below 0. If your GPU is between 60 and 90C, I just dont see that happening. Have you pointed an IR thermometer to the end of the heatpipes? Are they seriously near or below 0C?

BTW, I thought most heatpipes didnt use water, but ethanol or alcohol.

They don't use water. It doesn't mean they are immune to state changes. They are under a different pressure inside the heatpipe and have different freezing and boiling points.

Hmm. perhaps you are right. Kinda ironic its too cold to cool your card.

I guess the obvious solution is move them inside and actually use the heat produced by it or at least inside a shelter of some kind that can warm up a bit.

Alternatively, Id consider making something even more ghetto based on cooler that has no heatpipes. Something like an old Zalman copper flower or VF700. If you have the room for it, even an old massive copper CPU heatsink. It might be inadequate at room temperature but I suppose most things would work at -15C :).

Only thing is it needs a small enough footprint to not be obstructed by any nearby components. Not even sure that I have any stock heatsinks floating around. 6:30am and way too tired to tear apart my room looking for heatsinks. I know I have a thermaltake big typhoon, but that uses heatpipes solely to transfer heat energy to the metallic fins to dissipate the heat too. I also believe I have a waterblock and an extra radiator, but no extra pump. z_z

I'll mess around with stuff this weekend.

The heat pipe appears to be doing it's job of moving the heat when things get hot. The problem is your fan controller is reacting much too slowly. It turned the fan off at the temperature it should of turned it on then waited until your GPU was cooking itself before turning the fan back on.

Also, in such a cold environment, 2875 RPM is much more cooling then you need and apparently more cooling than those heatpipes can take. Try slowing things down to just 1000 RPM or so and see if your pipes still freeze up. Ideally, you should be able to adjust RPM to keep everything just a couple degrees above freezing point.