Pelts not doing their job

[71skylark]

I just put 2 172w peltiers on a maze2-2 waterblock on my XP1900+, the temps are only about 15F below amibent now! testing for a dead one just running either one leaves it about 10F below ambient.
I put arctic silver on both sides of the peltiers and screwed them down in a crosshatch pattern, my cold plate is cold to the touch, but not frosting ice cube cold.
I'm powering it with a 56A 28vdc PS I got off ebay for $40, I turned it's adjustment down to 23v, is that not low enough for the pelts to function effeciently? Or could a power supply have a "weak" rectifier that isn't giving me clean enough DC for the pelts (I don't have an occiliscope at the moment, and easier way to check this?"). I might try buying a 500w dimmer switch to bring down the voltage and see if that helps, but this system was supposed to be subzero.

[wolfsid]

Originally posted by 71skylark
I just put 2 172w peltiers on a maze2-2 waterblock on my XP1900+, the temps are only about 15F below amibent now! testing for a dead one just running either one leaves it about 10F below ambient.
I put arctic silver on both sides of the peltiers and screwed them down in a crosshatch pattern, my cold plate is cold to the touch, but not frosting ice cube cold.
I'm powering it with a 56A 28vdc PS I got off ebay for $40, I turned it's adjustment down to 23v, is that not low enough for the pelts to function effeciently? Or could a power supply have a "weak" rectifier that isn't giving me clean enough DC for the pelts (I don't have an occiliscope at the moment, and easier way to check this?"). I might try buying a 500w dimmer switch to bring down the voltage and see if that helps, but this system was supposed to be subzero.


so you have a cold plate between the pelters...

[Colin]

Check to see how many amps the pelts are drawing. It should be around 20 amps. It's also possible that your pelts may be slightly different thickness. And finally, pull your coldplate and check the contact patch from the pelts. I have found most pelts are concave and require a bit more thermal compound in the middle.

[ButcherUK]

How much clamping pressure do you have on the TECs? You need LOTS.
The voltage should be fine at 23V, is this set on a dial or have you check that it's actually supplying 23V with the TECs connected.
A rectifier doesn't smooth voltage ripple at all so a weak one of those is not an issue (a rectifier is an AC-DC converter). For smoothing you want some big capacitors. 2000uF per amp is recommened for unregulated supplies. The only real way to check ripple is to use a scope.
If none of that works you might try using white paste instead of AS2, AS2 doesn't do well in low temp / high pressure situations - it tends to "foil" forming a thin layer rather than just filling the gaps.

[71skylark]

I'll go repaste the pelts and clamp the living hell out them, crack em' if I can. Their cheap enough. The supply has some 2.2 farad capacitors in it I can see through the fan, and with a digital multimeter it is 23.0v rock steady with the pelts on.
Did I mention the peltier on the GF2 isn't really that cold either, but that is just epoxied on, I'll use a elongated C clamp to apply some pressure to it and see how that works out.

[ButcherUK]

Recommended pressure for TECs is 200psi, that's 1000 pounds on a dual 172 rig. You will probably not be able to exceed that without destroying the treads on the maze.

[fuzzba11]

Sounds like those babies just aren't getting enough juice...I would get another power supply, even though that one sounds like it could put out plenty, it just doesn't seem to be doing so...

How do you have them hooked up? Each to it's own power hot/ground or both running off the same? And maybe the kind of wires you're using aren't doign the trick...it could be a number of things, but I was running a 122W pelt with my Maze2 off a regular 400W PSU and the cold plate got frosty almost instantly after powering up.

[Miss_Man]

How is the temperature of the water?
It should frost up pretty quickly, even when I powered them at 14v. Maybe the peltiers are not 172 watt actually?

[Colin]

Even if the pelts were not 172 watt, they should still have a Delta T that will cause the coldplate to get nice and frosty without any heat load from the CPU. If this is not happening, then its a PSU or mechanical interface problem.

Regarding foiling with Arctic Silver, I know there are a very few folks that have experienced this. I have tried to get it to foil with no success.

[Warlord2]

I remember reading somewhere about somebody having to replace some of the wire on the tec to be able to get enough joice..

does anyone else remember reading this?

[Colin]

If the wires to the tech are too small, you will know it. They will get hot!

One thing that I have found to be very helpful for running and diagnosing problems with pelt rigs is a Compunurse sensor on the coldplate. Not only does it let you see what's going on but you can wait until the coldplate is below zero before you boot your computer.

[71skylark]

Hmm, well, those of you who said my 24v powersupply was to blame get the prize. It made a sort of alcohol like smell for about 2 min, I didn't know what the heck it was. Then, it just stopped working. Tomarrow I'm going to try em' using 2 car batteries. As a side not, how do I attach larger wires to the tec, they seem to go right into it.

[fuzzba11]

Originally posted by 71skylark
Hmm, well, those of you who said my 24v powersupply was to blame get the prize. It made a sort of alcohol like smell for about 2 min, I didn't know what the heck it was. Then, it just stopped working. Tomarrow I'm going to try em' using 2 car batteries. As a side not, how do I attach larger wires to the tec, they seem to go right into it.

Just a note of caution...you might not want to use batteries, because batteries run out of power. Leave your system on, forget about the time or go out, batteries die, pelts become insulation, water heats up, condensation forms, heat kills chip, water kills graphics card. Not such a great scenario!

[71skylark]

well, until I can find another 40A 24vdc supply for less than $1700, batteries will be what I have to go on. The ebay wait begins.

[Robbie]

You can use the batteries, you'll just have to keep a car charger on them. Ya may want to use the 10amp charge while there running and 2 amps while it's not running.

Rob

[71skylark]

Wait a minute, using batteries I'm not really getting any better result. I checked each pelts amp draw individaully and the 172w pelts are only drawing 6.1a on a 12v car battery, the Imax on these is supposed to be 12a according to dangerden. I think I should solder some new wires on these and see if that fixes it, or else what else should I try?

[Holst]

Hmmmm......

ive thought of one thing you might not have.

Have you measured the two pelts to check that they are both the same depth ?

If there not then you wont get a good interface to the coldplate/waterblock.

You might have to lapp one or both slightly to get a even clamping pressure. Access to a micromiter or good calipers will be helpfull.

it does sound like your just not getting enough juice into them.
Two 12v car batterys should be ale to provide enough power (but not for very long with 350 watts draw), One 12v battery wont work (only half the volts)

I wouldnt tecomend attaching a charger to the cells whylst your powering your pelts from them, you will probably blow the charger up. plus you dont want to ignite the hydrogen from the cells charging inside your house (big bang!!!)

if you want to replace the wires then id use 12awg silicone wire, the same stuff you get on more expensive electric model cars. That stuff shouldnt get hot even with the amps your pulling.

[ButcherUK]

I wouldn't use batteries if I were you, get a new PSU and have a try. The main prob is almost certainly clamping pressure not voltage. Don't be so quick to assume that the voltage is to blame, in 99% of cases where TECs aren't performing it's clamping not voltage.

[71skylark]

could lack of clamping pressure also be the cause of the only 6A current draw?

[wolfsid]

Originally posted by 71skylark
could lack of clamping pressure also be the cause of the only 6A current draw?


With those pelters on there like that i have tried it and i must have done something wrong cuz i thought that you can't have pelters on top of each other without having a coldplate between them.. What are your temps with that setup you have both Idle and load...

[71skylark]

OK, these things are still not working right. I was running them in series, that is positive of one to the negative of the other, is it possible that trying to run that much current through them I damaged them somehow? Even now running them with their own positive and negative they only pull like 5-6 amps each, which is less than half of what they are supposed to draw.

[71skylark]

Believe I found my problem, the wires that were on these peltiers were not getting hot, but after replacing them with some 14ga speaker wire, they work ALOT better, but still not right, I'm only down to about 40F or 3C with 2 172w peltiers. I'm wondering if perhaps I should try lapping the coldplate and using something other than arctic silver II. Where would I go about getting some of that danfoss compound I've heard about?

[SeigeAkicksass]

you may consider getingsoem different peltier (diff brand or somthing) i know it dosnt seem likehtat is the problem but maybe itis just athough

[Warlord2]

3c is a pretty good temp

you may try lapping the coldplate and the waterblock if you really want to get desprate but donno if the temp will change any

[Gliderguy]

If you run the pelts in series then each one is only getting 12V. if they are supposed to get 24 V each you will have to run them wired parallel. This would help explain your low current draw.

I dont know much about pelts specifically, so if they are run in parallel you may have to have some kind of electrically insulating material between the two of them. if they are conductive on both top and bottom you might short your power source (batt or otherwise) when stacked and run parallel.

[SeigeAkicksass]

i think that last guy might have solved you'r problem maybe- i dont think pelts are conductive onteh top and bottom but make usre you wire them inparallel or els it wll effectr preformance- but then agin you tested just one also right? so maybe that is it