A couple of things still lurking in the gray cells that bother me… Yes, Palmer addresses the exothermic action of fermenting beer, and says it can run as high as +10. Then in the same chapter he says pick a spot with an ambient temperature of 65-72 degrees to place your fermenter, which is exactly what I suspect the majority of folks do. To me that suggests a fermentation temp that could (theoretically) run from 75 to 82 degrees. Not too many beers will turn out as desired with those temps.
Second, I’ve now convinced myself that placing a thermowell w/ controller probe in the fermenting beer is not such a good idea. Most controllers run with a 3 or 4 degree temperature offset, so the beer temp would be swinging up up and down. Plus, the lag time for the temp to reach the probe may cause the outer areas of the fermenter to be too cold before the controller shuts off. And trying to tighten the temp offset just makes the compressor work harder. I guess I’ll just have to manually monitor the internal carboy temp and adjust the ferment chamber temp accordingly.
I’m glad we had this discussion! 