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NoL's TEC Guide: Guide 1 Basic Principles of TEC's

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Originally Posted by NoL at the Hardware Asylum Forum
TEC / Peltier Cooling Guide 1: TEC / Peltier Basics.

Peltier cooling, also known as TEC cooling, is another option for computer cooling, that can be combined with either water cooling or aircooling to create negative temperatures. Quite often an overlooked option in today's forums, it used to be the leading cooling solution of ORB benchers. There are not that many kit options out there, most of which are outdated and are not suitable for most current computers.

NOTE: This guide won’t be telling you which kit to purchase or how to set a system up, nor will it be pointing fingers at other kits for all of our amusement. Instead, I will seek to explain this mysterious form of cooling, how it works, and why it’s still a usable solution.

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I’m going to split this guide up into a few parts to make it a little bit more understandable to the naked eye.
1. The Peltier
2. Advantages and Disadvantages
3. Determining the sides
4. The Coldplate and insulation
5. The Hotplate
6. Cooling a peltier
7. Powering a peltier
8. Uses of peltiers



The Peltier

A TEC, or Thermoelectric Cooler, is a quite simple little thing that is composed of two different materials, usually sandwiched between two ceramic plates. A peltier is basically a pump for heat. One side gets hot, the other gets cold. Here's a good metaphor to describe TECs: In a room you have two cups, half full of water. Think of the water as heat. If you dump the water from one cup to another then you’d have all your heat on one side, and coldness (an absence of heat) on the other. (said the sentence that was here in the first sentence) The peltier effect occurs when an electrical current is sent through two materials that are dissimilar and are connected at two junctions. One junction gets coder as one junction gets hotter. The materials do vary from peltier to peltier company, but quite often it is plated copper and a semiconductor.

So following this principle, think of how the peltier will cool a CPU. Electricity flows from the negative pole of a DC power source through the peltier. The electrons move into the metal semiconductor and then through the second material. As the electrons move they pick up heat, and as they move to the other side of the peltier, drop it into the opposite side before producing down the wire to the positive side that the negative electron is attached to. The effect of all this electron work, is great overclocking temperatures while still being easy enough for the normal user to setup and without that much space being taken up. This process is also not perfect, and the more voltage running through the thermoelectric not only determines the peltiers heat output and amperage pull but will greatly effect the efficiency of the peltier.

A peltier works best at around 50% of its max rated voltage while being cooled properly. This is proportional slightly and not linear in overall wattage. This to say, a 160 watt peltier, running at 50% of its rated 12 volts at around 13.33 amps, at around 5-6 volts at around 6 amps, will move heat quicker and more efficiently than the same peltier at its 12 volt maximum but will move less heat. This is something to consider as getting a fairly large peltier (320-437 watts) and then undervolting it to run in the 160 watt range will heavily outperform, from an efficiency standpoint, a normal 160 watt peltier at 160 watts.

Peltiers also come in all different sizes. Custom peltiers can be ordered from certain manufacturers, but the general sizes are as follows:

40mm - Quite small, normally under 172 watts
50mm - The best size in my mind, normally no bigger than 320 watts
62mm - These are beasts, they come as large as 720 watts as far as I have personally seen.

Most gpu blocks are compatible with only 40mm TECs like the Danger Den Maze 4-1’s, and most cpu blocks are 40mm to 50mm, with some exceptions to 62mm. Wintsch Labs is one of the only block makers for 62mm blocks, and makes them for both cpu and gpu, but be prepared for a hefty charge and an even heftier charge to your electric bill.

Keep the sizes in mind though if your going to be using a pre-fabbed block, as size does matter, and nothings worse than buying something to fit a TEC and then learning it doesn’t actually fit that size.



Determining the Sides of Your Peltier

A peltier has a hot side and a cold side. These switch depending on the way power is run through the peltier. Simply hold the peltier between your fingers and turn it on for a moment. One side should get hot, the other cold. Do not run the peltier too long without cooling or you are risking its demise. An easy way to remember which side is hot is simply to take a pencil and put an H followed by a R or a B. If the RED power lead is the positive lead, then write HR on the hot side. If it is the BLACK power lead for the positive side, then write HB on the hot side. Remember, if you switch the power, the hot and cold sides will reverse. Its important to keep track of this when putting it inside your computer or the crap can hit the fan when you power up your computer.



Advantages and Disadvantages to TEC’s

The Disadvantages
The disadvantages to Tec’s are quite easy to spot right off the bat, so let’s clear those suckers out.
1) They are hot
2) They are inefficient (cut: at max voltage. they're like never efficient)
3) They require a dedicated power supply
4) They still require water-cooling for best results
5) The load temps can be quite bad
6) There isn’t a wide selection of water blocks
7) They are expensive
8) They are not as good as phase change (refrigeration)


Now that we got those out of the way let’s take a minute to see why these may be disadvantages.

1) They are hot

Every known form of cooling is hot. To remove heat from an area it really has to show up somewhere else. Tec’s just happen to be inefficient at moving heat so are hotter than most other solutions. But with a good water-cooling setup this really isn’t much of a concern.

2) They are inefficient at max voltage

Why are peltiers inefficient at max voltage? I can’t explain it really, but its easy to say a fix for this, get a bigger Tec, and run it below max voltage for a higher efficiency at the wattage you were looking at. Tec’s are inefficient but they are not terrible, and can still be used at max voltage when there may be no Tec bigger of the correct size or price.

3) They require a dedicated power supply

Most things do. It is that simple, the dedicated power supplies may be a tad pricey at retail, but most can be found on eBay at a more decent price.

4) They still require water-cooling for best results

This is just something your going to have to accept. Read Maxxx Racer’s guide if you're fearful of water cooling, but the only way to get rid of the heat produced by cpu/gpu and a Tec setup is going to be through a liquid medium. It is possible to chill the liquid, and even use direct die on a peltier, but at that point you may be better to just use the direct die setup directly on the CPU.

5) The load temperatures aren’t that great

A common occurrence with a peltier setup is when the system goes to load the temps of the part go into the positive region as the peltier isn’t so good under fluctuations of temperature and wattage. This is also because of the bland efficiency of peltiers, so lowering the voltage to the peltier and/or getting a bigger peltier may solve the problem as well as improve idle temperatures.

6) There isn’t a wide selection of water blocks

This is true, Tec cooling now in 2005-2006 isn’t a huge hit, and as I have said, overlooked. Another alternative to this is a challenge, design and create or have fabricated your own water blocks to fit peltiers.

7 - 8) They're expensive, and not as good as phase change.

Honestly, there not that expensive. A common saying is, “Phase change is just as expensive if not less than a good Tec setup and will perform much better.†For this point, a good Tec system will not perform as well as phase change, but will be less expensive if you don’t buy a kit or do some of the modding yourself. Also, a Tec setup will be part of a water cooling loop so you can also be cooling other parts of the system without having to get another single stage. On this point as well, Tec setups are generally smaller than phase setups and easier to fit in a case with your computers components. Another form of cost is in your electric bill. A common misconception is that peltiers take so much energy that they will raise your electric bill. Most power supplies used for powering peltiers suck less than a compressor for phase change.

The Advantages

Now to some more positive aspects of the Tec system. I wouldn’t want to discourage someone but those disadvantages and their counters are something to consider. Most of the advantages also do not require a large explanation, so I’ll list a few.

1) Negative Temperatures
2) Compact
3) Not so expensive
4) Easy to insulate
5) Fun to play with
6) TEC's CAN BE RUN 24/7!



The Coldplate

A peltier works better under clamping pressure, so it is generally sandwiched between a cooling solution and a Coldplate. The Coldplate is a piece of metal, generally copper [Cu], which adds cooling mass and distributes the heat to the cold side. A Coldplate can be from the size of the Tec to as wide as you need, but after a while it’s just a copper plate and not a Coldplate. The Coldplate is generally though, about 5mm bigger on each side of the Tec to allow for allowing mounting the Coldplate to the hotplate to crank on the pressure.

NOTE: On the cold side of the peltier, between the Coldplate and the peltier, use ceramique paste instead of silver thermal paste to avoid crackling and drying out your thermal grease.



Insulation

The big fat annoying insulation word is a fear of many, but actually this is a massive advantage over phase change. You only need to put about 5mm of neoprene on the back of the motherboard, and insulating the front is only required from the top of the Coldplate down. The actual cold spread that causes condensation on your motherboard is not that far as your cpu’s heat or gpu’s heat output keeps it in check. A base coat of nail polish followed by a sheet or two of neoprene or other insulation material can be all you need. Also, don’t be afraid to use di-electric grease.


The Hotplate

The hotplate of the peltier is normally a heat sink or a water block. Basically a peltier will move the heat from the cold side/cpu/gpu to the hot side so that it can be dissipated by cooling. There isn’t much more to this other than the following note.

NOTE: Between the hotplate and the peltier's hot side, use silver thermal grease!



Cooling a Peltier

A peltier produces quite a load of heat. It can be calculated as the wattage output of the peltier plus the wattage output of the item being cooled. So a 320 watt peltier chilling a 100 watt cpu will produce 420 watts of heat to the hot side that needs to be removed.

I will say that in almost no form is air cooling sufficient for a peltier system. Under 50 watts if your cooling ram with a Tec, but otherwise it is not sufficient. Water-cooling is required. Again, read Maxxx Racer’s guide to learn more.

I will also advise that starting a Tec/Peltier system with no prior water-cooling experience can be a devastating experience; do not attempt a peltier system unless you are comfortable with water!

There are a few water blocks that are peltier compatible: the Maze 4 series from Danger Den, some Switftech blocks, and all Wintsch Labs blocks. There isn’t much selection and each charges a pretty penny. If you have designing experience or access to a for sale forum this is where it may be a necessity. Let your creativity soar, design a new block, and get it milled. Share it on a forum and have someone else mill it, or go to a local machine shop.

NOTE: If you choose to build your own peltier water blocks, surface area is the key. Impingement over a 50mm area will not work without some insanely expensive high-heat dumping pump; even an Iwaki is no use there. Take a look at the Swiftech MCW6000/6002. It is a pin based design and doesn’t require a huge pump. Designs like that are great as they maximize both internal and external surface area.

Also, a peltier represents a lot of heat dump into your water loop so it’s important to realize that a single 120mm fan radiator isn’t going to cut it. Dual 120mm probably isn’t enough as well. A big strong radiator is required. A bip3 or two, a bix3, a 120.3, or two pa160s is something to consider for the commercial department, or a set of dual heater cores from Danger Den or a local car parts dealership or some Weaponized heater cores. A full peltier setup will put a drastic load and your water loop needs to be able to accommodate.



Powering a Peltier

Peltiers take a flow of energy from a dedicated power supply, usually. A normal computer power supply can supply the 12 volts that most Tec’s need, but usually lack adequate amperage levels on the 12volt rail. Modding a power supply is an option, though bulky and opening power supplies can be dangerous. The other option is something built for the task. At radio shack for $99 there are HAM radio power supplies capable of 14 volts at 25 amps. Perfect for peltiers. Another line of retail products is the Meanwell or Mean well series. They can be bought at Danger Den and other sites that stock peltier blocks, but are pricey. Check eBay once in a while to catch a good deal. Also, connecting peltiers to molex’s can and most likely will kill the molex and wire and may destroy the power supply. I will be creating a “Mod Your Own PSU Guide†in the near future for all the DIY’ers.



Uses of Peltiers

Let your imagination run free. Cool a cpu, a gpu, cool your ram, chill your Northbridge. Anywhere you can fit a water block, most likely you can fit a peltier water block. The only limit is your wallet, your skills, and your sanity, so get chilling and develop some new ideas to keep me busy.


Conclusion

Hopefully you now have a better idea of how peltiers work and you are considering a peltier setup or maybe a new peltier block design. Its now almost all in your hands. I will begin work on Guide 2 and Guide 3 in the following week or so, so don’t fret. TEC’s are far from gone.
A big thank you goes out to NoL at the Hardware Asylum Forum!

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Quote:


A typical thermoelectric module is composed of two ceramic substrates that serve as a foundation and electrical insulation for P-type and N-type Bismuth Telluride dice that are connected electrically in series and thermally in parallel between the ceramics. The ceramics also serve as insulation between the modules internal electrical elements and a heat sink that must be in contact with the hot side as well as an object against the cold side surface. An electrically conductive material, usually copper pads attached to the ceramics, maintain electrical connections inside the module. Solder is most commonly used at the connection joints to enhance the electrical connections and hold the module together.

Most modules have and even number of P-type and N-type dice and one of each sharing an electrical interconnection is known as, "a couple." The above module would be described as an 11-couple module.

While both P-type and N-type materials are alloys of Bismuth and Tellurium, both have different free electron densities at the same temperature. P-type dice are composed of material having a deficiency of electrons while N-type has an excess of electrons. As current (Amperage) flows up and down through the module it attempts to establish a new equilibrium within the materials. The current treats the P-type material as a hot junction needing to be cooled and the N-type as a cold junction needing to be heated. Since the material is actually at the same temperature, the result is that the hot side becomes hotter while the cold side becomes colder. The direction of the current will determine if a particular die will cool down or heat up. In short, reversing the polarity will switch the hot and cold sides.

Leads to the modules are attached to pads on the hot side ceramic. If the module is sealed you can determine the hot side without applying power. With the module on a flat surface, point the leads toward you with the positive lead, usually in red wire insulation, on the right. The bottom surface will be the hot side.

Material researchers are investigating the use of other materials to improve the efficiency of thermoelectric modules but Bismuth Telluride remains the most economical material for cooling modules used in ambient temperature applications. However, at low temperature (around minus 110 degrees Celsius) this material stops becoming a semiconductor and performance is severely diminished. Typically, the highest temperature that modules can operate is the melting point of the solder inside, usually + 150 or 200 °C (302 or 392° F).

Some Bismuth Telluride based modules for power generation applications are fabricated with high melting temperature solder or without solder entirely that can be used at temperatures up to + 400 °C. Hi-Z Technology, Inc. has some interesting and helpful information on this subject and manufactures modules of this type.
http://www.electracool.com/moduleworking.htm
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post #2 of 12
Very helpful, Cheers
Sticky?
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post #3 of 12
Stickied Good find Pinhead. It's a great place to start if you're completely new to TECs.
    
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post #4 of 12
good find that is a really good read.
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post #5 of 12
Very informative, best illustration i've seen yet, got it nailed!
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post #6 of 12
good information
thanks
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post #7 of 12
good information
thanks
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post #8 of 12
nice info, im hoping that ill be able to use it well for my upcoming pelt system build. By the way, does anyone know where I can buy a 60mm compatable waterblock?
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post #9 of 12
Thread Starter 
You can email Devin from Wintsch Labs for an Arctic Web. I'll PM you with his address.
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post #10 of 12
Good job.
Cooled my OCed 300A with a peltier and watercooling up to the point of condensation. But power has increased so much by now that it seems inpractical.
In combination with a SLI system, you're likely to draw over 1 kW of power..
On the other hand, the delta t is very appealing.....
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