Johnson A421 Controller, Hisense Chest Freezer, Thermocouple, and Frozen Carboys - Beer, Wine, Mead, & Cider Brewing Discussion Community.

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Well-Known Member
Jan 17, 2011
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Colorado Springs
Haven't had this happen before, but I have two batches of lager that I found frozen this morning. I was using a Johnson A421 controller in conjunction with a chest freezer. I have used both before for a half dozen batches or so, without problems. I had already completed the diacetyl rest and had been dropping the temp a couple degrees every few days, biding my time until my next brew day when I would transfer to a secondary and repitch the yeast into another two batches. When I went down today to drop the temp for the last time, I grabbed the controller, which is sitting off to the side and I think I saw 23 degrees on there. But when I grabbed the controller, I had hit the buttons and the screen changed, so I really didn't think anything of it until I was going to swirl the carboys a bit, as I typically do. Ice. My temp range, which I checked, had been set at 45 and 48 degrees. My other chest freezer is set up with a Johnson A419 temperature controller and I have never had an issue while using that one for the past five years. Setup has the Johnson A421 controller, a Hisense chest freezer, and a thermowell. Two carboys are both glass. As it appears the temperature controller was reading 23 degrees when I picked it up and my intended settings of 45 and 48 were still set, there is some sort of problem with the system. Whether it be on the Johnson controller side or the Hisense chest freezer side, I will have to investigate that later. Right now, I am just going to let those carboys sit and slowly unfreeze. There appears to be no cracks in the carboys at this point, from what I can tell. I don't know if they are fully frozen or if the ice is just along the sides of the carboy. I'm not going to pick them up at this point, as I don't want to put additional stress on the carboys. Same with the temperature raising...I'm going to close that lid here in a bit to allow slower thawing in hopes the temperature gradient across the ice does not spike from too quick a melt. The beer should be fine if the carboys hold...fermentation was complete at that point and had a good 28 days (or more) of fermentation time as I had adjusted the controller settings at that point. I would like to know if anyone else has encountered a similar problem with either the A421 or the Hisense (Costco purchase) chest freezer.
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