I am modifying a mini cooler/heater to turn it into an incubator in which I can program the temperature sequence in time. I have reconstructed the electric diagram of the cooler/heater and I don't understand why the maker chose to include the circled diodes. Here is the diagram:
There is a switch which controls whether the heater works as a cooler or as a heater, resulting in the two different wirings shown in the figure.
The wiring would be as in the figure above, depending on whether it's a cooler or a heater.
My question is: is there a reason to prefer the maker's design to the one I propose?