So I bought a 7cu. ft chest freezer this summer so I can control my fermentation temp. My dad had an old analog Dayton controller lying around for me to use. I placed one of those portable weather stations to see what the temperature differential was, and setting it at 58F seems to give me 57F to 72F range.
From what I gather on here, 15F is a huge temp swing for a controller. I'm not sure if I want to use it like so and hope that active fermentation, along with the probe not being near the fermenter, mitigate the temp. swing of the wort.