Temp in fermenter

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Feb 7, 2019
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I found a good deal on a small fridge freezer unit I would like to ferment in. I have a Johnson temp controller I can use, but with the freezer on top providing the cooling for the fridge below I'm not sure how efficient it would work. Just wondering if anyone actually knows if the fridge setting is all the way up - what is the upper limit of temp it would have without a controller?
Typically the fridge setting tops out in the mid-40s°F, which is why external controllers (or, adjusting built-in thermostats) is a thing. Yes, all but exotic top-freezer units generate all the "cold" in the freezer section and meter it into the fridge section as needed, starting the compressor (to chill the freezer section again) as necessary.

I've always used top-freezer fridges for fermentation chambers with external controllers (I have three of them even now) so I'm curious what you perceive as the down side...

I assumed since the cold making part in the top and the temp sensor in the bottom part were separated by a small duct with maybe a fan, the temp variances or swings would be greater than my chest freezer. I don't intend on using a heat source so I was concerned about the temp stability.

Thank you for the info
The need for a chamber heater is pretty much dictated by the yeast used vs room ambient temperature. If the fridge sits in a space that gets appreciably cooler than what the yeast you use desires, then you may need a heater. I have fan-driven 40W ceramic "reptile bulb" heaters in all three fridges as my humble brew space can get down below 60°F in the winter while most of the yeast strains I use are happiest between 64 and 67°F and almost all can use a good 68°F D-rest...

On my top freezer unit I took an angle grinder and cut out the divider between the freezer and fridge. Gives me more room to work with inside, and it's all 1 temp now.