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Watercooling system not performing well: Part 2

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Apr 25, 2001
Well guys thanks for all the help. I wasn't able to get the temps to read any lower, but when I took the block off it didn't look like I had good contact. Feeling adverturous, we decided to hook the peltier up. Idle temp 800@1008(112x9.0) 6-10C. WOW! Lets see how it looks under full load. It jumped up to only 32C pretty quick.... then slowly.. slowly made its way to 40C... That seems like a pretty big difference..? Heres the system stats again:

DD Maze2-1
156W Peltier on 300W AT PSU
DD Cube Radiator w/ Panaflo 120mm (70cfm) pulling & 2x80mm (35cfm ea) pushing
Danner 700gph
Arctic Silver I on CPU and Radio Shack goop on pelt

My first guess was that there wasn't enough air going through the radiator, so I took one of those rotating floor fans and pointed in the radiator.. didn't help. The peltier should be getting pretty good power off that 300W PSU (its a quality PSU) granted that its getting a little less voltage (rated 14V). I read once that a peltier should be double the heat your CPU is giving off (61W radiate)...?

Thanks for any help with part 2 of my problem!

Err, you using a coldplate? Maybe your DDCube radiator in undersized for handling a peltier. DD WC kit owners, anyone?

Yeah, you'll need to add the electrical heating of your peltier to the total amount of heat that needs to be removed (Heating=I2R, R=V/I).
I am using a coldplate. The MAZE2-1 comes with a nice screw-on coldplate that sandwitches the peltier. My setup is similar to the DD kits so it should be able to handle it...

It's not impossible for a peltier cold side to reach 40'C or 100'C for that matter -it's just a sign that the pelt is working harder than it can handle. Either the peltier is not rated for this kind of load (what is your pelt's rated wattage?) or the contact between the CPU core/plate/pelt/plate/waterblock is 'loose' or the WC system itself is not suited for the task (prime suspect: radiator. What are the dimensions of the radiator? I'm not familiar with DD kits).
Your radiator should be able to handel the load, like you said, just make sure your blowing cold air through it.

How does your water flow look ? I have a 300gph pump and now I have great temps.

PIII 733 idel -10C
load 3C

*edit* didn't see the danner 700 before, sorry. That's a good pump for the job. Maybe your flow is too fast ? You could try puting a valv on the output hose of the pump any try to slowly close it a little bit to slow down the flow of water. That would give the water more time to cool down it the radiator before it goes through the block again.

One more thought, whats the order of your setup ? I didn't see the last post so sorry for any repeat questions here.
The peltier is rated at 156W 14V. Its running at 12V. Heres a paste for the cube:
Outside: 4 3/4" x 5 3/8" x 4 3/8"
Copper Core (No Battery Effect)
Use with 3/8" Tubing
4 row / 15 pass
35 Aluminum Fins
Perfect fit for a 120mm Fan

The waterblock is held down to the board with 4 nylon bolts and the springs are tightened to almost complete compression. That should be enough preasure to make good contact.

I have always heard that the cube can handle a lot.. maybe I just need to give it more air? I suspect that the water isn't being cooled well enough, because initially under full load it jumps to 32-ish, then very slowly goes above that as it stays under load.

The order is
Pump -> Block -> Radiator -> Pump
it is a closed loop, with an expansion tube at the top. I've tried constricting the flow with my fingers (pretty tiring!) and it didn't seem to do much, although a valve might work better. Colin has always said that the Danner 700 + DD maze and cube gets optimal flow rate.

Some ppl have reported that at lower flowrates, their rigs actually cool the CPU better. You may try throttling your pump down a bit or use a slower pump. A 156W pelt should be quite a handful...
You want might want to change to this order :

Pump -> Radiator -> Block -> Pump

Just to make sure that the cpu gets the coolest possible water. also you pelt might be running at only like 110-120 w since it is running from 12 volts. and also do you have a load on the 5 V line to make sure that your 12v really IS 12v.

and not to forget, make sure that your waterblock is securely attached to your pelt, is securely attached to your coldplate to your cpu with good contact and termal grease (as2). there is many places that you can loose one or a few degrees just by having not 100% contact...
Unfortunately, I would have a pretty tough time changing the plumbing at this point.

Right now the 300W PSU that powers the Pelt also powers 5 coolings fans, which I assume are 12v... maybe I should hook these up to my normal 330W system PSU to take some load off (the original idea was to take load of the systems power). Also, how does running 5V make the 12V higher? What could I hook up that would draw from 5V?

Just hook up a 1 ohm resistor marked at 50w so you are sure it can take it.

It's because the 5v and 12 v line comes from the same switching circuit in the PSU. and according to a few laws of electronics the switching circuits will lower a highly loaded 12v line ito compensate for a low load 5 v line. I will not go into the details , but this should make it understandable. there are a few articles out on the web about this. if you want to be sure, just measure your 12v line with a volt meter or multimeter.
OK, so connecting a 1 ohm 50W resistor to the 5V line (yellow wire) should cause the PSU to give the 12V line a little more of its power back? Radio Shack should have that kind of resistor right?
They will probably have it. and you might want to meter your 5 and 12 volt lines to see exactly what you get...
Things to note. Your pelt is probably drawing 11 amps at 12 volts. The 300 watt PSU needs to have enough juice for this. The plumbing order is ok. The Mag 7 does not add that much heat. My temps actually went up when I put the radiator between the pump and block. BTW, your water temps should go up about 10C with the pelt but the radiator can handle it. The extra fan is a good idea.

I would suggest pulling the coldplate off and checking the contact area of the pelt. Every pelt I have used has been slightly concave and required more thermal compound. You should get idle temps of -5C or better and full load temps under 20C. If you have a Compunurse or other digital thermometer, put the thermistor on the cold plate. This will tell you what's really going on.
yeah, just make sure the resistor's wattage is high enough or you'll start a fire. Also I noticed you said you tightened the nuts on the Maze block until they were almost compressed, might want to tighten them until they are completely compressed. I found that it takes almost 6lbs pressure to completely compress the springs so that adds up to 24lbs pressure so completely compressing them should be ok. Just be careful and don't go past compression too much. 10ºC with a peltier at no CPU load seems pretty high.
My 4 pronged power cables have a red, 2 blacks and a yellow. I have a 12V LED running off the red lead. If I soldered the pelt to the 5V line that would explain a few things! I wish I had a multimeter or something. Could it also be possible I'm still getting bad thermistor readings? When I feel a small exposed area of the coldplate with my finger it feels very cold even though MBM says 37C. The temp also fluctuates quickly between 35 - 37

I also want to mention the chip. Its in pretty bad shape after the last year. 3 of the corners of the core are chipped off, and theres chips out of the edges of the core too. I lapped it a little though. Its also filthy =P

One recommendation:
go to radio shack, pick up the resistor, AND a cheap a$$ multimeter. you will need one, and dealing with pelts, it is rather important to know the exact currents and voltages.

If you spend a few extra bucks on teh meter, you might be able to pick one with a temp probe up. look around, they are cheaper than you might expect.
Well, heres an update for you guys. We had infact connected the peltier to the 5V lead and not the 12V. We switched it over, and tried it again. We got great temps! -2 idle 18 load. Then the PSU died, after putting off a very strong burning-electronics smell. It was a pretty good quality AT style 300W. Now I need a good replacement unit to reliably and safley power that peltier. A 400-500W AT style PSU would be perfect (since it would fit in our case and have a switch) but if we have to use a specialty power unit I guess we just have to. Thanks again to everyone who has been helping...

Glad to hear you found the problem. Your temps are where they should be. Too bad about the PSU though...........