Cooling a e6600 Conroe with a TEC

[THE JEW (RaVeN)]

Of course since we're talking high Amps here, especially on TEC, let see this pic below and let say from your installation you measure the voltage at 2 locations which is at at the power supply output and at the TEC termination cable like this.
View attachment 55704

If your result is really like that, I would say you must dump that cable since it is dropping 1 Volt across it ! For high current device, it is very-very bad !

How bad ? Let see....

Let assume from the manucature specification that the TEC is running at 15 Amps when at 12 Volt.

The voltage at Tec at 11.995 Volt which is very close enough to 12 Volt and it is quite safe to say it is also consuming 15 Amps as per factory spec.

Now, the voltage right at the power supply output is 12.995 Volt (yeah, assuming it is a bit off) and through the cable it drops 1 Volt across it and arrived at the TEC at 11.995 Volt.

This means the cable alone is eating up the power at -> Watt = Volt x Amp = 1 Volt x 15 Amps = 15 Watt !!!!

The TEC power -> 12 Volt x 15 Amp = 180 Watt vs 15 Watt , see how bad it is almost 10 % of power used by that dumb cable !

That is why most high current devices got hunky cable to minimize this voltage drop and also if possible make it as short as possible since we don't want it to act as a stealthy resistor that steal up the power !

Say, just for a moment, you wanted a cable to consume that much wattage. What would its characteristics be? I'm thinking a large diameter and quite long, correct? As small diameter cables pose a fire hazard, I'm hoping that to be the case.

Why would I want the cable to consume some of the wattage? Well, I would like to run a 437watt TEC but around 18 volts. The problem is that I only have a 24 volt power supply (well, actually it's 2 X 12volt ones that I'll wire to give 24volt) that can only drop to about 20 volts delivery. If a long, wide cable would drop that another volt I could could get closer to my goal of 18volts.

I had a thread over XS asking about voltage reduction ( http://xtremesystems.org/forums/showthread.php?t=134757 ) but it didn't seem to come up with any new ideas on the subject. I'm just looking at cheap, easy ways to increase the efficiency of TEC's.

 

[bing]

Say, just for a moment, you wanted a cable to consume that much wattage. What would its characteristics be? I'm thinking a large diameter and quite long, correct? As small diameter cables pose a fire hazard, I'm hoping that to be the case.

Dropping a voltage (or deliberately using a cable to drop a voltage) is a really bad method.

Yes, that is why on small cables has higher resistance that makes them vulnerable to catch fire when passing high current. That energy they consumed is transforming into heat. Again, no good.

Why would I want the cable to consume some of the wattage? Well, I would like to run a 437watt TEC but around 18 volts. The problem is that I only have a 24 volt power supply (well, actually it's 2 X 12volt ones that I'll wire to give 24volt) that can only drop to about 20 volts delivery. If a long, wide cable would drop that another volt I could could get closer to my goal of 18volts.

Well, if you really want to drop a voltage, do it using resistor as above illustration. Since the occured heat will happened at the resistor which is easy to control instead of heating the entire cable length ! e.g.: How do you know at which spot along that cable will start to heat up or worst catch fire ? This is not good for heat management especially inside the computer casing.

With resistors, you can simply can control where you want to put them, again the word is "control" the heat where you want it to occur, not putting your luck at that cable.

Again, you need to know how much current that Tec is operating at 18 V, since if the spec is 437 watt at 24 volts, it doesn't mean at 18 volt the wattage will be reduced accordingly using simple ratio in math.

By using method as above, testing with different values of resistors, you will find the sweet spot that drops he "exact" 6 volts as you expected, it should be easy as long you have those different resistors. Good luck.

PS : There are so many methods, but this resistor method is the simplest one.

 

[speed bump]

Say, just for a moment, you wanted a cable to consume that much wattage. What would its characteristics be? I'm thinking a large diameter and quite long, correct? As small diameter cables pose a fire hazard, I'm hoping that to be the case.

Consider wires the same way you do tubing in your WCing system.

As far as getting you Tec to run at 18v why not just buy a PSU that will supply 18v?(as long as that doesn't exceed its vmax.). If you can its usually easier to regulate using the output rather than resistors.

 

[datura3]

I had a thread over XS asking about voltage reduction ( http://xtremesystems.org/forums/showthread.php?t=134757 ) but it didn't seem to come up with any new ideas on the subject. I'm just looking at cheap, easy ways to increase the efficiency of TEC's.

How much efficiency would you gain running a 437w (24v) TEC at 18v compared to a 320w or 226w (15v) peltier at 13v? I'm curious, because I feel like running a 437w tec at lower volts will not work as well as a 226w at full volts, mainly because the 437w is 62x62mm and the 226w is 50x50mm. Will it be significantly more efficient to make it worthwhile? That will be interesting to test. I'm also interested in Bing's method for voltage reduction to run different peltiers on the same 600w PSU. i.e. running a 172w (24v) and a 226w (12v). I just picked up a 600w, 24v PSU for 40 bucks to test out some of these other TECs.