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I am making an electrical fridge for a school project. I am using a 12v Peltier cooler and using a 12v 30a power supply. I have all the wiring and everything already set up, and no matter what I cannot afford to have the Peltier burn out or anything even though I had one burn out before using the exact same setup and wiring, though that was a smaller model still 12v, but the Peltier isn't working at the cooling power that its supposed to be. it cools down the fridge to 68° f when it should be cooling to 20°f, and I think it might not be getting the power it needs, but the wires that I'm using are extremely small, like 22 gauge, but I have them doubled up, one concern I have is that the input and output wires for the Peltier warm up a lot, but not enough to melt the wires, even though it melted the wires for the first Peltier that burnt out. The reason I'm going into such detail is that I know basically nothing about electrical things like that and want to know if the context matters and I really need to know what the warm wires are because of, and more importantly if it would be safe to use thicker wire.

Update: I do have a lot of cooling on the hot side, I have a CPU cooler meant for a computer on the hot side, so there isn't a problem with that, but the first time that the Peltier burnt out it didn't have any cooling at all and was extremely hot. Also, I am also wondering if a wire too thick would damage or cause the Peltier to burn out? Like I said before, I can not afford no matter what fo have that Peltier burn out.

Also, my power supply's input is 115 or 230 but I keep it on 115 because I don't want the thing to burn out just in case that matters

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  • \$\begingroup\$ Find an online ampacity calculator. \$\endgroup\$ – Ignacio Vazquez-Abrams May 9 '18 at 5:17
  • \$\begingroup\$ Using thicker wire is absolutely neccessary in this case. \$\endgroup\$ – Long Pham May 9 '18 at 5:19
  • \$\begingroup\$ Too many charges trying to move through a narrow wire too fast. Causes the wire to heat up. Technical term is current density. When you run a wire with too high of a current density, it will get hot. \$\endgroup\$ – mkeith May 9 '18 at 5:20
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If the wires are warm throughout then the gauge is too small. But if the wire is too hot close to the unit that tells me the unit is too hot and the wire is heated by conduction of the heat not from the copper losses.

I suspect your problem is lack of cooling on the hot side . These devices only generate a temperature difference between the hot and cold side so if you don’t remove the heat with the fan and proper heat sink on the hot side then the cold side will not reach expected temperatures. Please measure with this thermometer both the hot and cold side of the device and not just the air temperature. You also need a conduction plates for the cold side in order to spread that heat absorption or cooling effect. Please report your test results. Using a CPU heatsink and fan and use AWG16 wire. The closer you can get the hot side to room temp, the colder the inside will get. Even try water cooling plumbing or use mineral oil instead of water with a tiny pump to a reservoir

or a like they do in Mercedes SUV options make a car beverage cooler and warmer for cold and warm beverages on each side with a copper or alum sheet cylinder on either side !! Probably a $500 option hah

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    \$\begingroup\$ While I agree, I also think he is using wire that is much too thin. Note how he says he burned up the wiring previously, and he also says that he is only using AWG22 wire, yet it is a 30A power supply. That doesn't seem like a good match. \$\endgroup\$ – mkeith May 9 '18 at 5:24
  • \$\begingroup\$ Well there is enough cooling on the hot side, and now I know that the wires are too thin, but if I make the wire to thick, will it burn out the Peltier? And if so, what gauge wire would you guys recommend for my project. \$\endgroup\$ – Erik Low May 9 '18 at 5:31
  • \$\begingroup\$ 3 gauges lower reduces temp in half , 6 gauges lower reduces temp to 1/4 etc etc \$\endgroup\$ – Sunnyskyguy EE75 May 9 '18 at 5:34
  • \$\begingroup\$ If you use correct V , I should be correct \$\endgroup\$ – Sunnyskyguy EE75 May 9 '18 at 5:42
  • \$\begingroup\$ @ErikLow You can always make the wires thicker. All that will do is reduce the resistive losses in the wire itself and make the wire a bit stiffer. The first is what you want and the second won't matter unless there is movement or the wire needs to make an awkward bend. \$\endgroup\$ – ratchet freak May 9 '18 at 9:08
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Feeding your peltier to much current will counter the cooling effect with internal resistance, causing excessive heat past the units recommended max amp, and risk burning it out. A current limiter may be required to save the cooler with that massive power supply, you probably only need 4-5 amp per element at 12 volt. These things last longer when changes in temperature are gradual and slow (relative to a on/off thermostat) and that includes pwm´s slower than 10Hz (10 per second switchings). Your wire may be to thin as I do not use gauge but mm2 I do not know, but if you limit your current perhaps not, if they still get warm please increase thickness as other poster suggested. Good luck on your project.

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