IMO, the best way is to set the freezer control to max cold and let the controller do the controlling. After all, that's what you bought the controller for in the first place. Locate the probe near the floor of the freezer and away from the freezer wall which contain the evaporator coils. The reason I suggest the probe be located near the floor is that this is where the air will be the coolest. We are drawing the beer from the bottom of the keg, so the probe will also be in close proximity to the actual poured beer. I'm also not in favor of placing the controller probe in a container of water as this does nothing other than increase the response time for the controller. You can accomplish much the same effect by increasing the differential setting on the controller if your controller has this feature. Don't be afraid to set the differential fairly high. IOW, setting it very tight at say 1 deg F is not necessary in order to maintain the beer at a stable temp. It will, however, cause your compressor to cycle more frequently which is generally not good for it. I'm currently running some tests in order to get a better handle on the optimum configuration, but I've found that there are a lot of variables to deal with, so it's taking some time. A lot of time actually and I still haven't quite figured out how interpret the collected data. Such things as the compressor cycle frequency vs. power consumption vs. temp swings vs. probe placement vs. differential settings vs. circulating fan vs. no fan vs. fan running continuously vs. fan running intermittently vs insulated collar vs un-insulated collar vs ambient temperature etc, etc. As you can see, it gets rather complex very quickly. I think what it will all boil down to is the bottom line power consumption. I'm guessing that a wide differential setting with the probe mounted near the bottom, insulated collar and no fan at all will yield the cheapest operating cost while still maintaining the poured beer at the desired temperature. However, I think that the best configuration, at a slightly higher operating cost for me, will be with the fan running full time, a 5 deg differential, insulated collar, probe at the bottom of the freezer. I want the ran running to help cool the beer lines, shanks and taps which are located near the top of the freezer where the air temp would be significantly warmer without the fan running full time.
