Finally received the last op-amp from mouser, which has allowed me to run tests on the board. After a number of air-wires to sort silly mistakes the board is working as expected. I will post the TINA model of the op-amp circuit that is useful for checking the feedback / set-point system.

The TEC ic runs quite warm, this may be due to having it connected to a 1A supply, rather than the 3A it will be getting. I know that from other peoples experiences that current limiting the supply can result in dead chips.

The DAC is behaving correctly, although I need to look into setting it to default to mid value at startup; 0.75v which corresponds to ~25'C. This ensures that if there errors in control and the unit is enabled before the DAC is set that the TEC should not be put into over-drive heating.

I've updated the board to fix errors and add selector for DAC address and optional components - variable resistor instead of the DAC, to allow manual temperature setting, without need for Arduino etc.

Fig. test setup, heatsink on hot side, thermistor under foam on cold side