Boxing & Watercooling to Silence

Do-It-Yourself Systems
December 17, 2002 by Michael Greene (michael at greenes.com)

I like my computer. It's an Athlon XP-2000 that I upgraded from an older 1400 Mhz Athlon. My primary use for it is to grade children's arithmetic tests (http://www.mathability.com) which puts the machine through its paces. The grading algorithms literally read the children's handwriting using a variety of OCR strategies that soak every cycle the machine can offer up. The downside to the machine's capability is it needs to be fed watts and relieved of the associated heat. That leads to noise - something I've grown to despise as I've aged.

I originally attempted to minimize the noise by building a large wooden box for my computer, water cooling the CPU to minimize fan noise and carefully routing the air through the box to minimize ventilation fans. For $200 and a few hours of work, it was a solution that worked on a 1400 Mhz Athlon. The CPU temperature would hover around 36C and it was quiet. I wrote this up in an article for overclockers.com.

Time passed and faster CPU’s came out. The 1400 MHz CPU was capable of reading a 90 question test in about 3 seconds and I figured an XP-2000 would shave about a second off that. When I upgraded to the XP-2000, I was back to square one. The box couldn't move enough air to keep everything cool. After about 10 minutes, I had to operate with the side door off which of course let the noise out along with the heat.

At that point, I started wondering if maybe moving the water out of the box and passively cooling would help keep the box cool. I had seen a reference to using a large 5 gallon pail as a reservoir and figured it was worth a try. It didn't work well enough. But heck, maybe if one pail wasn't enough, maybe two would be better. Nope, not enough. Finally, I had three 5-gallon pails full of water passively dissipating the waste heat from the CPU. I used a small Rio pump to move the water to the CPU and two 3" diameter flexible tubes to siphon the return water between the pails.

The temps, as reported by the Gigabyte GA-7VRX motherboard, would stabilize at around 38C for CPU and 34C for motherboard. (The manual doesn’t say if the motherboard reads the XP’s temp diode or if it’s using an onboard sensor so actual CPU temp may be higher but the 34C case temp is probably accurate.)

Unfortunately, about two months into this, I noticed a musty smell in my office. I lifted a lid on one of the pails and sure enough, mold was growing on the inside of the lid. An architect friend of mine suggested I come up with a better solution before the mold got into the walls so I started scouting eBay. I figured if I wanted passive cooling I was going to need surface area comparable to what the 3 pails had provided. A car radiator would fill the bill. A few days of watching the radiator market on eBay and I found one that was perfect. A brand new Modine radiator built to fit in a 1989 Chrysler for $5 - who could ask for anything more? Ebay is amazing.

A surprise bonus when the radiator showed up was discovering the radiator was pure copper. My waterblock is copper so I had been thinking about a sacrificial anode to handle the corrosion issue but that turned out to be unnecessary due to the all-copper radiator.

I wanted a simple tie in to my computer's water lines so I opted to place the radiator flat. I needed some kind of mount to lift the radiator off the floor so air could convect up through the radiator. My goal was to provide as clean an airflow path as I could for convection purposes. Four 50 cent plastic pipe connectors and some cable ties were all I needed. Well not quite. I added a couple of feet of packing tape to keep the pipe connectors from splaying apart when I set the radiator down.

I connected the radiator to the water lines by filling the radiator with water and then dipping the feed line into one end of the radiator and the return line into the other. It took me two tries to siphon the feed line to an Eheim 1048 water pump. Siphoning is required because the Eheim needs the water feed line to be full before you turn the pump on. A few feet of plastic wrap was all I needed to keep the water from evaporating out of the radiator and feeding any nascent mold wafting about from my last eXPeriment.

As I type this, the main noise I hear is a puppy a few houses down the street that is unhappy he's not getting any attention. The 350W Whisper Enermax is fairly well shrouded by the box but still audible. At this point, it’s the main noise source from my computer. I have two old 20G hard drives whose noise is completely damped by the box. I upgraded my water pump from the slightly noisy Rio to a dead silent Eheim 1048.

The only way the water pump makes its presence known is by an odd, low frequency thrumming in the water block - I can't hear the pump itself. Again, the box masks that noise as well. I can’t tell you how many decibels it’s generating as I don’t have a meter. The noise is audible but if a faucet drips 40 feet away, I can still hear it. I've another Athlon that's air-cooled and it's several times noisier than this machine. That machine is only on when I'm scanning tests and is turned off immediately thereafter. Heck, even the refrigerator is noisier than this box.

There's a bit of work left to do in ventilating the box - I have to open it when the work load gets heavy. The CPU temperature hovers around 38C and the case temp is around 34C. When the CPU is heavily loaded, the temps slowly climb so that after about 20 minutes the CPU is at 43C and I have to open the door again to let the heat out. With the door open, the temperatures will drop. (Editor's Note: Michael obviously takes a conservative approach to CPU cooling. I am sure many readers here have allowed XP temps to reach much higher -- 85C for me, and it still lives.)

One idea I've yet to try is opening up an ATX power supply and sticking waterblocks where ever I see a heatsink. That would enable me to dump the fans in the power supply without it overheating. I tallied the surface area on the radiator and it works out to about 6500 square inches. At a guess, the Chrysler radiator could easily handle the additional heat load. If not, I can always add another radiator. But that's a project for another day...

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