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First Tec setup

Hey everyone,

First of all, sorry for my bad English, but I'll trying to do my best .
Good here is the situation.

I have a tec of 504W, that can cool 300W on heat. It's a 31.6V, and draw 16A of the psu...
Now, my psu is a 24V 300W industrial psu that can provide 12.5A.
I know, the psu is waaaaay to small for the tec, but it has a Volt regulator, so I can turn the voltage down for 15%.

Now I'm asking, is my calculation right?
I'm studing math, so I cant do it just like that .

31.6V*16A = 504W
504W @ 31.6V, but he is 24V

24V/31.6 = 0.76*100= 76% of the cooling potential@24V.
300W*0.76 = 226W on Cooling potential of the tec.

Now, The amps is going down as wel with 24%
So, 16*0.76= 12.16A
And 12.16A*24V = 291W that he pull of the psu.

Is this right?

I asked on an other forum, and hel gived me this calculation:

TEC: R= U/I = 31.6/16 = 1.975 Ω
24 V: I= U/R = 24/1.975 = 12.15 A

So, the numbers are the same, but I wanted to be absolutly sure...

Quote:
Originally Posted by Tommienator

Hey everyone,
First of all, sorry for my bad English, but I'll trying to do my best .
Good here is the situation.
I have a tec of 504W, that can cool 300W on heat. It's a 31.6V, and draw 16A of the psu...
Now, my psu is a 24V 300W industrial psu that can provide 12.5A.
I know, the psu is waaaaay to small for the tec, but it has a Volt regulator, so I can turn the voltage down for 15%.
Now I'm asking, is my calculation right?
I'm studing math, so I cant do it just like that .
31.6V*16A = 504W
504W @ 31.6V, but he is 24V
24V/31.6 = 0.76*100= 76% of the cooling potential@24V.
300W*0.76 = 226W on Cooling potential of the tec.
Now, The amps is going down as wel with 24%
So, 16*0.76= 12.16A
And 12.16A*24V = 291W that he pull of the psu.
Is this right?
I asked on an other forum, and hel gived me this calculation:
TEC: R= U/I = 31.6/16 = 1.975 Ω
24 V: I= U/R = 24/1.975 = 12.15 A
So, the numbers are the same, but I wanted to be absolutly sure...

Ohms law doesn't apply to tecs. The amps will change as the dt and hotside temps change.

Your better off finding the manufacturers performance chart for that particular tec.
Quote:
Thermo elektrisch koelelement.z.g. TEC of Peltier.
Koel vermogen max. 300 Watt
Aansluit spanning max. 31,6 Volt
Stroom max. 16 Amp
Afmetingen 50 x 50 x 3,1 mm
Lengte aansluitdraden ca. 60 mm. Teflon
Max element temperatuur 200 °C

It's in dutch, but i'll think that you can understand the important things...
But I've checked it with this...
And with my calculations it' all right... (not with the omh laws but with my percent calculating.)

So, is it possible ?y
I will use it for 24/7 on a i7 860 @ 4.3ghz.. With HT off.. (I know, it was a mistake back in the times, I had to buy an i5)
So it has a TDP of +- 190W if I calculate it with this
And the tec wil be cooled with a RX360 & 240 rad

Or waths going to be the most effective?

If I do a tec direct on the cpu...
Or make a chiller of it?
Than I can cool the tec with the RX360, and cooling my cpu first with the 240 rad that the water is cooled for about 26°C and than true the tec that is is chilled.. Or this isn't going to work?

Edited by Tommienator - 5/6/12 at 7:03am
You can expect at most 5-10ºc below your water temps with a single tec of that size pushing 190watts.

The single rx360 should cool that tec.

with a single tec dd or chiller is a matter of preference.
mmh, my water temps is always around 20/25°C with the RX240&360 rad.. @ full load.
But, with wath 5/10°C? the chiller or DD?

The chiller seems easyer to make, but wil it coole just for max 10°C? if the water is around 25°C... For a 226W tec it seems not much..?
Quote:
Originally Posted by Tommienator

mmh, my water temps is always around 20/25°C with the RX240&360 rad.. @ full load.
But, with wath 5/10°C? the chiller or DD?
The chiller seems easyer to make, but wil it coole just for max 10°C? if the water is around 25°C... For a 226W tec it seems not much..?

qmax = watts moved at 0dt

you calculated 226w qmax and your calculated heat load is 190watts. You don't have alot left for that tec and that doesn't include losses the thermal resistance in your design.

with a single tec direct die and chillers are about the same in performance.
mmmh, thx. I tought it will cool beter as chiller... Becouse I take a lot of heat away by the rad, and than te tec can chill my normal room temp water...
But yeah, I'm thinking for the chiller solution !

My last question...
Can I use anny waterblock for te tek? I want to use 2x EK LTX blocks, is this possible?
Quote:
Originally Posted by Tommienator

mmmh, thx. I tought it will cool beter as chiller... Becouse I take a lot of heat away by the rad, and than te tec can chill my normal room temp water...
But yeah, I'm thinking for the chiller solution !
My last question...
Can I use anny waterblock for te tek? I want to use 2x EK LTX blocks, is this possible?

You can apply ohm's law and use that PSU. I have done similar things. But as Mindchill said, you need to be careful that the effective resistance (voltage/current) of a TEC will change with its working temperature. Luckily in this case as the TEC cools, the hot side gets hotter and the current will decrease with the same input voltage. If you leave 10% headroom on your calculation you will be fine.

Yes you can use two waterblocks, provided that they are large enough to cover the whole area of the TEC. This is crucial, otherwise the TEC could be damaged.
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 Obsidian (22 items) TEC block on 4770K ! (34 photos)
CPUMotherboardGraphicsRAM
i7-3930K ASUS P9X79 Deluxe XFX HD 7970 Black Edition Double Dissipation Patriot Viper Xtreme Series 4x 4GB DDR3 2000 9-...
Hard DriveHard DriveHard DriveCooling
OCZ RevoDrive3 X2 OCZ Vertex 4 WD 640GB  Swiftech 360 Radiator
CoolingCoolingCoolingCooling
MCP 35X pump Swiftech Apogee XT waterblock Foxrena's Water Rack KOC TEC and Fan controller
CoolingOSMonitorKeyboard
KOC 62mm TEC block Windows 7 Ultimate Dell UltraSharp IPS 27'' 2560x1440 Razor Black Widow Ultimate
PowerCaseMouseAudio
Corsair AX1200i Corsair 800D Logitech G9X Logitech Z4
mmmh, thnx... I'm going to see wath's giving me the best temps... The tec right on the cpu, or as a chiller...
But I'll think if I use the tec as a chiller, it is interesting for further expands of my WC, if I cool the graphic card etc.

I have al the materials, so doesn't matter really .