I had some egregious temp control problems in the last two batches -- my Ranco temp probe taped to the side of the fermenter got dislodged and I found beers to be about 30 F-ing degrees higher than I wanted! (The F stands for Fahrenheit). So I got a thermowell, thinking this would help ensure this never happened again. And I decided to test out my new method with water before I brewed another batch of beer... I filled a bucket fermenter up with 5 gallons of water last weekend and hooked my Ranco to a heat mat wrapped around the fermenter. I slipped the thermowell through the airlock grommet and slid the Ranco probe into the thermowell. Set it to 70 degrees, and came back a week later (today) and measured the water temp as 75 with my Thermoworks RTC600 thermometer. I calibrated the RTC600 against ice water and it is reading 32F, so I am inclined to believe the 5 degree difference between the actual water temp and the Ranco setting. I had a blanket over the fermenter thinking it would help insure against temp swings. What's the explanation for the discrepancy, do you think? Is the fix to just adjust the Ranco setting to lower than where I want it? Note: I am now testing it at 65 degrees, without the blanket. I'll check on it later this week.