Submerging the Thermocouple

Hey everyone, I have seen a one or two peoples pictures of their kegerators/keezers and the temperature contoller thermocouple is submerged in a liquid, either water or ice-pack gel. Is this superior to having the thermocouple sensing the ambient temperature of the freezer? Is the liquid a simulation of what the beer temp is inside the kegs? would my compressor cycle more or less often? I think what the main goal is is to have your beer temp at a steady stable temperature. I dont know whats goin on here...

anyway, whats up with the submerged thermocouples?

I think its not just to simulate a bottle of beer but also to provide some thermal lag, at least for the thermostats that dont have a differential option. so basically all the theories you have are correct.

Basically, you only care about the temperature of liquids (beer) in the fridge, not temperature of the air in the fridge. Submerging the probe in a fluid (I recommend mineral oil as it won't evaporate or harbor mildew bacteria) will prevent the kegerator from cycling as frequently b/c air temperature is more likely to fluctuate than the beer temperature. This prevents it from kicking on every time you open the door.

Do you have to do anything to the probe to make it water proof or are they manufactured that way?

You would have to check the thermocouple. I know some of them say not to put into liquid. Mineral oil is not ideal in the fact that it's density is relatively higher then beer. I would put into water. I use water in a sealed container which I then parafilm (really good plastic wrap) around it. You could get a decent price on a tube drill the cap to fit the thermocouple into it and then just plastic wrap around it and you should get no bacteria ever.

i just stick my thermocouple in aquarium hose sealed it at one end with a little heat and works like a charm.

Its as you said to keep the temperature the same and not drift, if your beer is at 40F, and you open your lid and it senses your at 60F...when you close the lid it might take 10-20 minutes to get the air to 40F again, by then your kegs which were already at 40F have been subjected to 20 minutes of sub freezing temperatures, putting them way below your goal.

Water and other things take time to change, even if you opened your lid the water would barely change at all, thus not causing your freezer to turn on when it shouldnt.
Many people who measure taping to the side of a keg/carboy(fermentation chambers) make this mistake in when they put in a new keg they move the thermocouple to the new keg, which then causes your freezer to turn on trying to cool that new keg down...freezing every other keg that may have already been in there.