Thanks Day and Fuzze - something weird is going on. I definitely have the hot side bridge removed. I had tested it when I built it and was able to control each independently. In doing some troubleshooting this morning, I power-cycled everything and upon boot only the cold outlet powered on and not the hot. BrewPi says it is idling, but it is still trying to cool, even when BrewPi is set to off. My first two fermentations did almost exactly what I wanted them to do, even without having implemented a heating element. Is it possible my Arduino board went bad or a relay is stuck?
Are you using a relay board or SSR's?
If your using the relay board, is the little red LED on for the cooling relay?