Failure modes?

Can they fail open? Maybe not (assuming the wires are good). I think all of the elements are in parallel

https://electronics.stackexchange.com/questions/261655/what-happens-when-a-peltier-fails

Firstly, it appears that peltiers often slowly decline according to the referenced article, with increased resistance and decreased heat pump capacity.

Therefore, my proposition is that in a typical heating application the heat produced by a perfeclty-shorted 100W peltier would be the equivalent of a 50W, poorly back-insulted, resistance element.

Power supply: roughly 12V @ 8A.

TODO:

• Try cooling using external pump + power supply

AKA: Silicon Thermal Powercool CH250

something like 28V @ 5A

10 TECs in series

Measured one TEC: 4V @ 1.4A start voltage

TODO:

• Verify expected resistance (10 * 2.4 ohm ⇒ 24 ohm)
• Try cooling using external power supply + pump
• Backup PIC firmware?
  • Might also be useful to figure out serial protocol

TEC:

marlow
industries, inc.
(/P)

DT12-6 L

47348

USA
- +

I found DT12-4 and DT12-8 datasheets. Looks like linear relationship. Interpolated datasheet:

• dtmax: 66 (27C), 74 (50C) C
• Qmax: 54 (27C), 58 (50C) W
• Imax: 5.55 A
• VMax: 14.7 to 16.4 V
• AC resistance: 2.4 ohm

Reference: https://photonlexicon.com/forums/showthread.php/6533-Thermotek-Chillers-Exposed!-(TEC-Question)

• Well I finally concluded that the 10 TEC's inside the unit were 45W each with an Imax of 5A. So I found a set of 10 45W TEC's on ebay for $65 with an Imax of 3A. Obviously more efficient. Nothing wrong with that! So, I just received the new TEC's last night and proceeded to put the ThermoTek chiller back together again.
• let them sit for a bit then check the resistance of the good modules
• i found the 40-60 watt TEC's to be around 2.8 ohms. 140 watt 0.8 ohms
• Also, 25W is a damn small rating for a 40 mm TEC, you can expect that and more out of a 22mm TEC. I think yours will likely be 50W each. Give or take 10W. Hard to tell from here, but looking at the ratio of column (pellet) width to gap width can be a guide, if you compare with others to hand. (thicker columns=higher current).
• Also, all 10 TEC's are run in series to the 28V supply.
• Anyway, It does sound like you have a bad TEC PS especially if the relays are engaging. Any funny smells at the board? Maybe one of the transistors on the heatsink or one of the filter caps are smoked.
• External power to the TEC's 22 volts @4 amps this thing gets the water temp down fast!