If the controller has two channels (one for cooling and one for heating) simply plug the freezer into the cooling side and your heating device into the heating side. Plug the controller into the wall socket. Set the controller to the desired temp per the instructions, place the temp bulb inside the fermenter chamber, and it will decide which channel to turn on/off.
I’ve seen a light bulb in a can, a ceramic reptile heater, heat wrap, etc used for the heat device.
I hope this helps.
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