@landshark
You can calibrate these units. It's a +- function in the menu of the controller. They are good cheap units. I'm using to directly wired to a couple fridges. The only issue I've had is with a power fluctuation I've had it not turn back on for some reason when the power came back on. The unit was fine but need to be unplugged and plugged back in to start working again. Luckily it's only happened twice, but the first time it got really hot in the fridge while I was fermenting before I notice the controller wasn't running.