I finally got to brew again this weekend! So far, the cabinet has done very well. I'm attempting to hold this batch at 68F. I pre-chilled the cabinet with about six 2-liter ice bottles (4 in the water, 2 in open air). That got the cooling water down around 40F. Once I was ready to put the 5 gal carboy (pre-chilled to 68F) of sweet pre-beer into the chamber, I swapped out the 4 ice bottles that were in the water with fresh ones. That drove the temp down to 35F and left plenty of ice in the water. So it has been about 50 hours now, and the cooling water temp has raised from 35F to about 37F. From my previous tests, this curve will start accelerating, but I think I still have a few days left on this first batch of ice. That's pretty cool in my book!

The jury is still out on how best to monitor the carboy temp. I did circle around and make a pretty snug (and pretty big... like a 4-inch cube) insulation block to shelter that sensor from the chamber air. I think I've greatly reduced the influence of the air temp. The spikes on the carboy temp are only 1 to 2 degrees, and they are changing so suddenly that I don't think it is the actual liquid... I think the glass around the sensor is cooling, and that is leaking in. I really didn't want to make a liquid-proof sensor for the carboy side because of the contamination risk. I may just have to live with this for now. I've cranked up the temp polling to every 45 seconds, which is about as quickly as I can cycle through them all. So the fans aren't staying on very long... Usually just one polling cycle. The temp difference started out about 35 degrees between my cooling water temp and my target temp, so the chamber air where the carboy lives is getting a pretty good blast of cold air, and the carboy temp continues to drop a degree or two over the course of several minutes after the fans are spun down. I've pondered taking the temp delta into account and not leaving the fans on for an entire polling cycle if it was very great, but a degree or so is within the range of this particular yeast and it is still way better than what I had previously been fermenting with (see the red line for that!)... So I may just leave well enough alone for now.