Fermentation temperature,Interesting discovery

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Bombers hoppy ending

Well-Known Member
Mar 19, 2021
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So I’ve just stated brew 4, and have been making some modifications to kit as I begin the learn more.
I had been hoping to be able to ferment and bottle condition in the same fermentation fridge, but found that the initial layout wouldn’t give me a high enough temp split between FV and bottle section.
A 2nd heater and fan were purchased and set up in the bottom of the fridge space. Then having carried out a few experiments found that bottles in the bottom, FV in the top, and the temp prob attached to the FV, gave me the temp split I wanted. FV could be kept at 18.5C and the bottles in the bottom were enjoying 22-23C. Very pleased with that.
Monday I bottled brew 3 and started brew 4. Set the fermentation fridge space up, FV in the top and bottles in the bottom, and shut the door. ST-1000 set at 19C.
Result was a surprise.
Fermentation started 12hrs after pitching and was very active by 24hrs. FV temp is holding a very constant 19.2C but the bottle area at the bottom is only 16C.
I first thought this odd as the heaters are in the bottom so should be a warmer area. Also odd that the FV is above set point. Not seen that during previous brews. The system has shown no over shoot of temp.

Explanation appears to be that the fermentation is exothermic enough to maintain 19.2C without external heat required. This has meant no heat to the bottom of the fridge meaning it’s cooler than the FV.

It’s going to be interesting to see that as the fermentation begins to slow and the FV begins to cool, that heat will be required to maintain 19C and the bottle area temp will begin to rise.

If this is the case this could be a nice way to track fermentation progress by monitoring the change in temp at the bottom of the fridge.
Plan is to log the temp of the bottle section each day, and see if there is any correlation to CO2 production, bubbler activity.

Every days a school day.

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