Temperature probe location

[pelipen]

Wow!! Love all the data! Sounds like I run a similar set up...a temperature controlled water bath using the STC-1000. One side controls an aquarium heater and the other controls a pump. The pump sends water from the water bath through an immersion cooler sitting in cooler of ice water and returns it to the water bath. I just tape the submersible probe to the side of the fermentor. I have a question though....I ferment in a stainless Sanke keg. I would think that the SS keg would have much better conductivity than glass or plastic fermentors. In other words I wouldn't be getting the swings in temperature, or at least not as much, using stainless. Your thoughts?

we have a pretty similar setup. You're using a heat exchange method, I'm pumping cold water from one container to the other. The cold water is in a cooler, I pump to the bottom of the container holding the carboy. A pump in the carboy container circulates the water at a slight upward thrust to get good mixing. The drain is at the top, and constantly recirculates the water back into the cooler as long as the cooler pump runs. I periodically recharge the cooler water with blocks of ice.

Stainless conducts much quicker. I can see that in my kegs, the temp drops immediately. I haven't figured out a good way of measuring core temp in kegs under pressure, so I also use a block of insulation cut to fit the prob exactly, exposing one side slightly, then I strapped it down to the side hard, so it's well sealed.
I think with stainless, during active fermentation, your temp differential should be less than with glass or plastic.

 

[pelipen]

I have an analog Johnson controller that I thought was a 3 degree differential but I will have to check. With that controller if I put the probe near the carboy but not attached and I set it at the low end of the yeast recommended temperature do you think I will have too large of a temp swing. I could then increase the temp setting after a couple of days as the wort becomes less active? Sound good?

I have found that during active fermentation, the core temp of the beer floats along the top of the water bath peaks, then eventually falls to the middle. So I do exactly that, I set the controller one degree cooler than I want, then as fermentation is less active, I set it back up one degree.
I wish I could set these to half a degree, because it's possible to sustain temps within less than half a degree with the right setup.
As long as you have a fan in there blowing the air around, you'll be fine. Without a fan I think you would find the carboy warms up the air in a zone around it. I haven't measured this, but that's what I would expect.