adding a peltier to a watercooling loop to increase cooling

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adding a peltier to a watercooling loop to increase cooling

Postby aussiejunior » Mon Feb 15, 2010 3:56 am

Hi guys. Recently during our summer I have run inito a smidgen of a problem with my waercooling setup. Here in Aus where I live it is not uncommon for us to reach 40c plus tempretures and on days with anything over 34c my watercooling setup struggles to cool my cpu even at stock settings, i have seen temps as high as 70c.
What I'm thinking of doing is adding a peltier to the watercooling loop to increase the cooling potential. Is it possible and whereabouts would I add the peltier?
Sorry for the fairly vague question, but I am still new to custom cooling setups and the local shop here are a bunch of idiots who wouldn't even touch my computer when I asked them about adding watercooling to it.

The setup I am using to cool the cpu is a colermaster aquagate max with a swiftech apogee cpu block and two coolermaster 90cfm fans. It's been a great setup untill the heat really kicked in during summer lol.
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Postby thomas_w_bowman » Mon Feb 15, 2010 7:41 am

If you have a container for the water outside of the PC, I'd place peltier there and add cooling (heatsink, or fan/heatsink) directly to the reservoir (peltier/heatsink/fan). Since some peltier units draw more amps than you will want to draw from the PC PS, I'd power that seperately as well.

Since some peltier units may drop temps below freezing, a thermostat may be useful to avoid freezing (or to conserve energy if room temp is adaquate to cool PC).

A water/peltier 'hybrid' would be good to minimize risk of condensation (depending on humidity), you don't want water condensation to be dripping inside of the PC.
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Postby fussnfeathers » Mon Feb 15, 2010 8:25 am

Also bear in mind that TEC coolers are designed to work at 16v......more than a computer PSU puts out. They'll RUN on 12v, sure, but at about half the cooling efficiency. And you have have have have to cool those as well, you can't just stick a TEC somewhere in the cooling line, and run it un-cooled, give in a day and all the connections will melt.

Thomas is right on the power draw. Not all are alike, but in general, a TEC plate will draw around 24 amps, tho I've seen some older ones that cut off at about 20 amps. Note that this is not dependent on usage! They draw that much from a cold start, no matter how hot the CPU its cooling gets. Given you already have a watercooling system that's powered off the 12v rail, I would look into getting a supplemental PSU just for the TEC. http://www.crazypc.com/products/7250.html is a place to start looking, and don't forget the relay switch to turn it on with your regular PSU. Just remember, that's still a 12v PSU, so a TEC module rated to transfer 70c will only do around 30c.

Which Swiftech block did you get? Those need to be mounted in a specific direction related to the processor socket, otherwise they work like garbage. Given that you're seeing temps that high, doublecheck that you have it in the right orientation.
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Postby aussiejunior » Mon Feb 15, 2010 2:55 pm

I have a swiftec gtz cpu block. And what I was thinking was maybe straping the peltier directly to the radiator??? That way the fans from the radiator would cool the hot side?

And yeah I was thinking of getting a supplemental power supply unit for it.
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Postby fussnfeathers » Mon Feb 15, 2010 3:05 pm

That's not going to be enough cooling for the peltier. Figure that it's generating that much cold on the cold side, it's also generating the same amount of heat on the hot side. You wouldn't put a case fan in front of an unprotected CPU and expect it to run very long.

Cooling an object from room temperature to freezing is a typical thermoelectric application. As an example, assume that the object (electronic device or picnic box) produces or takes in from the environment 20 watts of heat. A thermoelectric cooling module will remove this 20 watts via its cold surface and deposit it on its hot surfaces. This 20 watts plus the power input to the TEC must be transferred to the atmosphere by means of a heat sink. A fan is recommended to put on a heat sink. Selecting a proper heat sink is very important when you design a thermoelectric cooling system. Usually, temperature of a heat sink rises 10ºC above ambient temperature after TEC applied a proper voltage when the cold side of TEC is without any heat load. You MUST increase the size of heat sink and fan or reduce voltage input to the TEC to achieve better performance if the temperature of the heat sink is over 10ºC above ambient temperature when no heat load attached to the cold side of TEC.

In other words, unless you have a hefty heatsink on the TEC module, it's going to burn up, it doesn't shut down like a CPU does when it reaches critical temps. Typical application in a PC is to mount the TEC between the processor and the heatsink, using either a bolt-through HSF with enough thread to do that, or somehow modifying a stock HSF bracket.
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Postby aussiejunior » Mon Feb 15, 2010 4:57 pm

so i could place the tec unit with the cold side on the cpu and use the watercooling to cool the hot side then?
core i7 920@4.0ghz
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Postby fussnfeathers » Mon Feb 15, 2010 8:03 pm

Could do. The obvious thing to watch out for is condensation. TEC's get cold. Very cold. They can frost over. If that happens, and you either have a spike in temps that lowers the watercooling effectiveness, or you shut the machine off completely, you'll have a problem. That's partly why TEC's have never taken off, except for embedded systems in extreme conditions that never shut down.
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Postby aussiejunior » Mon Feb 15, 2010 11:22 pm

lol, i dont know that frosting over is going be a problem here in my house lol, if it's 38c outside I can guarantee it will almost be the same inside, ah the joys of having a house with no insulation or aircon lol.

But as far as insulating the motherboard goes it won't be too hard to isnulate the parts that the peltier could potentially get water onto. Eithr a few peices of thick foam or some of that art putty eraser stuff should do the trick.
core i7 920@4.0ghz
asrock x58 extreme 3
6 gig ocz ddr3 1866mhz @ 1600mhz
evga gtx 460 1gb external exhaust *2
Creative x-fi xtreme gamer
custom watercooling loop for both cpu and gpus
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Postby fussnfeathers » Tue Feb 16, 2010 5:07 am

Be careful with that, you don't want to insulate things around the socket. Those caps get hot as well, they need to be able to dissipate heat.
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Postby thomas_w_bowman » Tue Feb 16, 2010 8:50 am

I'd want to keep the peltier chip outside of the case if I had water cooling. You may want to make a 'special' resevoir (perhaps with a side made of copper or aluminum to conduct the 'cool'), then firmly fasten the peltier unit to the side (or bottom) being sure you have a good heatsink/fan on the other side of the peltier chip. This would cool the water yet be much less likely to cause condensation.
Any containment of condensation can eventually overfill...
And a thermostat can be helpful to shut off the peltier unit when the water gets to perhaps 3-5c, resuming when water temp gets to perhaps 10-20c - so the thermostat would connect or disconnect the peltier PS from the peltier unit itself (a relay to control the Peltier PS).
Actually, sounds like fun...
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