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Old 01-29-2010, 02:49 AM   #1
Jan 2010
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is it true that the fermenting wort raises the temp in the bucket, if true... what temps will this start? how high would it raise? do you account the heat produced toward your reccommended ambient ferment temp for the yeast?

for example if i ferment a wyeast 2112 which needs 8-17 D C. would ambient of 14 actually be 14?

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Old 01-29-2010, 04:02 AM   #2
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Yes, fermentation releases heat into whatever vessel the wort is in - sometimes lots of heat. It can be as much as 4C. As to what temperature this starts, that is dependent on the strain of yeast. If you are on the lower end of the recommended range for the yeast, activity is slower and produces less heat. As you raise the temperature, the fermentation becomes more active and produces more heat, which in turn, raises the fermentation temperature even more. So yes, you have to account for the temperature increase in your ambient temperature. I try to keep my fermentations cool for the first 72 hours (peak activity) to make sure the temperature stays in control.

The heat increase at the peak of activity (and the off flavors it can produce) is why many homebrewers fight so hard for temperature control in fermentation. Some (including JZ) believe consistent, controled temperature during fermentation is the best way to improve the quality of your beer.
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Old 01-29-2010, 04:03 AM   #3
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i don't know if there is a standard 'start at x temp and finish at y' since the temp of the yeast will vary based on activity and i think that will vary by cell count and how much fuel they have to work on.

A lot of people have temp control units and fermentation chambers and such to keep the fermentor at a certain temp. If the probe senses the temp is rising above the desired level it will kick on the fridge or ac unit and drop it back down to the appropriate place.

One trick a lot of people use, especially in the summer, is to increase the thermal mass of the fermentor by placing the bucket in a trash can or something full of water. Adding bottles of frozen water will drop the temp in the bucket down and the large amount of liquid will help regulate the fermentor and prevent large temp swings.

A lot of people believe in the stick-on thermometers you can attach to the fermentor. In general, if you keep the ambient temp in the proper range for your yeast, then you'll probably be okay. If you keep your house in the 50s then you'll want to think about something to help warm the yeast. If you live in a house that resembles the tropics then you'll want to cool it.

If you want to take the time and spend the money you can find some nice designs for temp control, but if you can get the temp around the fermentor close, then you'll be fine.

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Old 01-29-2010, 03:31 PM   #4
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If ambient is 14C and the yeast range is 8-17C, you could easily exceed that with a strong fermentation.
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Old 01-29-2010, 04:19 PM   #5
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I use an aluminum foil tape to secure a temp probe to my carboy. If i cover the carboy with a couple of towels, it is not unusual to see an 8F temp difference between the carboy secured probe and the one left outside the towels during the heaviest part of fermentation.

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Old 01-29-2010, 04:24 PM   #6
Mar 2009
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Originally Posted by Tbaz View Post
is it true that the fermenting wort raises the temp in the bucket, if true... what temps will this start? how high would it raise? do you account the heat produced toward your reccommended ambient ferment temp for the yeast?
yes its true that an active fermentation will be warmer than the surrounding hair. how much warmer will depend on what kind of yeast and how active the fermentation is. yes you should account for the raise in temp from the fermentation toward your fermentation temperature.

this is why many of us use some sort of temperature control.

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