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-   -   Temp Caused By Fermentation.... (http://www.homebrewtalk.com/f163/temp-caused-fermentation-386933/)

Catfish1320 02-03-2013 01:47 PM

Temp Caused By Fermentation....
 
Are the high temps caused by the fermentation itself ever taken into consideration? For instance, I have a beer fermenting in a room that has varied 65-67 however, shot with a heat gun, the Carboy is at 78*. It's in strong ferment mode 2nd day. But it's still temp. Just wondering if this is the norm or do I have to ferment at lower ambient temps?

zachattack 02-03-2013 01:54 PM

Yes, most of us take that into account. You can get a cheap "fermometer" that will read the temperature on the carboy. And if you're using active temperature control, insulating the temp probe against the carboy is generally the best option.

What yeast are you using? A beer temp of 78 can produce some pretty nasty fusels. Also keep in mind that those IR thermometers can be fairly inaccurate, unless you input the specific emissivity of the surface.

JLem 02-03-2013 01:58 PM

Quote:

Originally Posted by Catfish1320 (Post 4859382)
Are the high temps caused by the fermentation itself ever taken into consideration? For instance, I have a beer fermenting in a room that has varied 65-67 however, shot with a heat gun, the Carboy is at 78*. It's in strong ferment mode 2nd day. But it's still temp. Just wondering if this is the norm or do I have to ferment at lower ambient temps?

You need to account for this increase - all the temps listed for yeast and in recipes usually mean fermentation temp (i.e. the temperature of the beer) and not ambient temp. Still, an ambient temp of 65F should be fine...an increase of 13F seems high. Is your heat gun calibrated?

Pappers_ 02-03-2013 01:58 PM

Yes, the yeast in their activity create a lot of heat. I don't know anything about heat guns, so can't comment on how accurate that is. You could get a stick-on strip thermometer and attach it to the carboy and that will give you a sense of the temperature inside it. I use a temperature controller and a chest freezer, and attach the probe of the temperature controller to the carboy - I stick it snugly underneath the webbing of the carboy carrier I use, so its held tight against the glass. For most of the ale yeasts I use, I start the fermentation temps at 60F and raise it up slightly as fermentation continues.

Before my current setup, I used a big rubbermaid bin in my basement - ambient temps in the 60s - filled the bin with water and put the carboy in it, then swapped out 1/2 gallon frozen juice bottles. I kept a floating thermometer in the water and aimed for 58-64.

Catfish1320 02-03-2013 02:39 PM

The yeast is wlp001. I was really surprised to see it that high also. I'm hoping the gun is just off. It's a good gun, but been around a while. Just in case, I moved it to another cooker area, and will be getting stick on thermometers real soon. Probably too late to worry about this one, but lesson learned.

beergolf 02-03-2013 02:44 PM

Yes yeast generates heat. From my experience if the ambient temp is near or below the low end of the recommended range for that yeast, the temp rise is usually only a few degrees. If the ambient is near or above the upper end of the temp range the temp rise can be 10 or even more degrees higher. I always like to start off at the lowers end of the temp range. The ferment is much easier to control that way.

Wynne-R 02-03-2013 05:21 PM

140 kcal/kg extract

10 lbs of grain is 4.54 kg, x .85 =3.86 kg extract which would yield 540 kcal.

540 kcal would raise the temperature in 19L (5gal) 28.4 C ( 51.1 F)

So there is enough energy to heat 5 gallons by fifty degrees Fahrenheit. Which is to say if the reaction occurred in zero time, if it went off like a bomb, thats what would happen.

I ferment in a water bath and in a well controlled fermentation the beer will be as much as 1.0 F warmer than the water bath in the first few days. Thats measured with a calibrated thermometer in a thermowell. I dont know what it would be in air, my guess is 10 times that.

BigFloyd 02-03-2013 05:38 PM

Interestingly enough, I just made a first-hand observation of the heat generated by active fermentation. I put a thermometer on the rack to see what the air temp is inside my upright freezer where I have a 5-gallon batch of Northern English Brown that's been there about 19 hours. It's bubbling pretty steadily through the airlock.

I have the STC-1000 temp sensor taped to the side of the bucket and insulated so it gets a good reading to operate the controller.

Ambient air temp = 60*F

Side of bucket temp = 67*F
(which is the temp at which I have the controller set)

In all likelihood, the temperature in the center of the batch is running a few degrees hotter than on the side.

I doubt that it has peaked so soon. I rehydrated the Windsor, but didn't do any aeration other that letting wort run out of the ball valve and splash into the bucket. I'll check it later to see if the temp difference is any higher.



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