[evolvedpc]

If overshooting your TEC's wattage capacity is such a big problem, why not just choose a really big TEC, with plenty of headroom. To avoid getting too cold, can't we just use a simple voltage step-down circuit to adjust to a lower hot/cold side delta if our CPU's heat output is lower than the TEC's capacity?

[NoL]

Because at some point you still have to cool all the heat of the processor and the TEC itself, while meeting clearance around the CPU socket and making a comfortable and usable mounting system.

A 62mm TEC comes almost to the point of being unmountable.

[evolvedpc]

Originally Posted by NoL

Because at some point you still have to cool all the heat of the processor and the TEC itself, while meeting clearance around the CPU socket and making a comfortable and usable mounting system.

A 62mm TEC comes almost to the point of being unmountable.

By "bigger" I mean higher capacity. Does a higher capacity TEC have to be physically bigger?

[Bobnova]

Generally, yes.
The difficulty is that it either has to be bigger or higher voltage, and finding a 400w 24v power supply is difficult and expensive.

The largest 15v i've seen is 50mm x 50mm and 400w@15v, about 260w at 12v.

[AlexanderB]

biggest I've seen is here on my desk, 62x62 480w @ 15 or 16v (don't recall, i have it written down somewhere) but if found out its impossible to aircool, you *need* water.

however, I've come to realise that even this tec is pretty useless, if you put it on anything "bigger" than a midrange card, the coldside is not gonna be much colder then straight watercooling, for example, my watercooled gpu (hd4870) gets about 40-45 degrees C load temp @ furmark, thats 200w into watercooling. putting the TEC inbetween, you'd need a much bigger, and very good waterblock, to take out almost 700w of heat, and it would get a theoretical 15-20 degree delta between hot and cold, however, I doubt that a waterblock can be made to absorb 700w at the same plate temp as my current waterblock at 200w, and whats the point of having the card run at 20-40 *C over having it run at 40-45 with regular watercooling?
so, adding a pelt to a hd4870 would be useless, and adding it to a slower card, it would be useless in the sense that its useless to slap hundreds of dollars to a cheapo card to make it run somewhat faster, while you can get a much faster card for much less then the total spent..

so... get a phase change unit for the same amount it would cost to pelt and watercool something, it works much better