220W question

[Golias]

I have received a new 220W peltier and would like to know if it´s possible to run it with 5v instead of the normal 12v

The peltier states that it needs 25A on the 12v rail.

[NitroRat]

sure you could, but it won't cool anything.

[Golias]

I have the possibility to acquire either a 156W or a 226W peltier, which should i chose for a Tbred 1700+?

So what you are telling me is that if a use anything lower then ther default 12v (5v or 7v) the peltier will not cool anything special.

I´m new to the peltier issues, but have some lights on the matter. Any sugestions on this matter?

[Oc2theSkY]

The 156w would probably be close to decent air cooling, but that is it.

[Golias]

So it´s 226W all the way.

I really have to get a dedicated psu that has 25A, i´m having a bit of a problem finding them here in Portugal. At least the ones that fit in a 5 1/4 bay.

[Tedinde]

sure you could, but it won't cool anything

Actually it will. I had a switch rigged up to go between 5 and 12 volts on a 1.6a almost 2 years ago with a 226 watt tec.

Wasnt much sense running 12v and 24 amps when just typing and whatever. And temps were staying around 23C. And down to -3C @ 12V.

Plus no worry if you went to work leaving the rig on.

[Golias]

So basically what you are telling me is that if i get a switch that alternates between maybe 7v and 12v, i will be able to maintain that system.

When you say 1.6a dont you mean 16a on the 12v rail?

EDIT : 1.6a is the CPU, jesus i must be sleeping.

What is the aprox. amperage in need to run a 256W 25amp peltier at 7v. I would probably say 16amp, is this correct?:rolleyes:

[NitroRat]

1.6 amd at idle 23c like i said won't cool anything ...

[Slickthellama]

wait a second, hold up.

226W<--- is max wattage

12V*25A=300W :eek:

not possible...
it will run at

226W/12V=18.333A

226W/5V=45.2A BUT! IMAX is 25A... so you will only get...
125W peltier

If your PSU can supply 25A on a 5V rail you are fine.

EDITED FOR CORRECTNESS TO ADD IN THE IMAX FACTOR.

[NitroRat]

would be nice if it worked that way but when you lower the input voltage you decrease the amps that it will use and it will not work on a 1.7 amd being pushed to 2.4. you want to try go ahead but you have been warned...

[sandman]

226 watts is the max amount of heat it can move, not how much power it uses.

At it's max voltage it will use 25A.

It would be somewhere around 15V and 25A.

[Tedinde]

Im using an external Pyramid 36 amp supply, Shows 24 amps @ 12v, but 11amps @ 5v. Volt and amp gauges on it, adjustable.

I was using a true power 550 with a switch like i said above. Best to get a dedicated.

[NitroRat]

thanks for the confirmation was going to set mine up and check the amps you saved me the trouble. thats about a 50 watt pelt dont think that would work too good on a cpu.

[Golias]

Thanks for the info guys, so for what i read if i use the peltier with 7v instead of 5 or 12 i would probably be using it has a ~156W peltier. That doesnt look too bad but only the temps will say.

[NitroRat]

no not even a 156 your looking at 100-120 watts at best. When you go below 11.5 volts efficency goes down and at 7 its way down.

[Jabo]

If you are usin following TEC:
Qmax: 226Watts
Imax: 15.4Volts
Amax: 25A

@12 Volts -> Qmax=180.8Watts
@7 Volts -> Qmax=105.46Watts
@5 Volts -> Qmax=75.33Watts

It's not 100% correct since relationship beteewn volts supplied and amps drawn is not 100% linear but is extremely close to it.
Lowering voltage supplied causes lower amperage consuption which in turn decreases heat pumping capacity of module.
We want as much heat pumping capacity as possible to get our chips as cold as possible. Why then run TECs @ lower volts than rated? 12v is PC standrd PSU voltage for starters, at Imax module produces massive amount of own heat introducing all of it plus chip poduced heat load into WC loop and most of WC loops are not capable of handling so much heat load.The last one is massive power draw and difficulties aith sourcing an appropriate power suply to handle such electrical power demend.
Conclusion -> if your WC system is capable of it run your TECs at Imax to achieve the best cooling of your sillicone.

On a side note, ppl seem to forget that insulation is EXTREMELY IMPORTANT in such applications. PCBs are mostly made of copper... o the more insulation covering the bigger area the better!

[Golias]

I hear what you are saying, and thank you for the info.

One interesting thing is that the peltier package does not include any type of silicone or anything other then the neoprene casingand a cooper plate. And the guy that sold it to me told me that his supplier told him that it was a "ready to go" package. I have my doubts.

You can have a look at it right here (http://www.aquapc.com/forum/viewtopic.php?t=7615).

[Jabo]

You can use silicone if you like but it's a pig to remove if needed.

Dielectric grease is what you want.

The best way to do it is to do it yourself. Prerequisit being your high manual working skills. All you need is lots of diff thicknesses of neoprene closed cell insulation (cell sizes decide thermal resistance - the higher the better - and physical properties like compressive strenght - too much force and cells will burst). Then you let yourself loose with sth VERY sharp (stop drooling ;) ) and cut your neoprene to suit your board, cpu, water block etc. The last but not least is some sort of clamping/fixing mechnism/methot to hold your contraption in place. When you finished you cover the lot with as much dielectric goo as possible and ... yes you may surf your fav p0*n sites staying cool :)

Enjoy