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Old 08-21-2012, 01:24 PM   #1
Guidry
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Default Fermentation Temps: Ambient vs Wort

Looking at building some type of fermentation system and one of the questions I can't seem to find a full answer on is the actual difference in temps between the ambient air in the chamber vs the actual wort. I have seen references made by various people saying that theis "may be as much as ___ degrees difference". I completely understand that. I'm wondering if anyone (seems like someone(s) would have) actually measured and recorded this kind of info.

My reason for wanting to know is my chamber design needs to take this into consideration. Example: If I need to be able to ferment at say 62 degs, does that mean I need to get my air temp down to 60? 58? 54? Down here in So. La, in the heat of the summer, that's a big difference.

Been trying to search for this info, but I haven't gotten lucky on my searches yet. Maybe one of you can point me to it?

Thanks,

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Old 08-21-2012, 02:55 PM   #2
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It really depends on the yeast strain. Some are wild and crazy yeasts (Hefe strains) and can spike 10* or more above ambient. Some are just little chuggers (Denny's favorite, in my experience) that barely get but 3-4* above ambient.

If I were you, I would size the chamber for the worst possible scenario.

However, I would like to point out that best practice is to measure the temperature of the wort, not the air. So after you get it built, be sure to actually measure the wort.

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Old 08-21-2012, 04:05 PM   #3
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I am leaning towards maesuring the wort temp. My next concern is the lag between air temp change and wort temp.

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Old 08-21-2012, 04:36 PM   #4
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Air temp will fluctuate fairly wildly compared to 5-6 gallons worth of liquid. I wouldn't be concerned with the lag so much as the differential.

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Old 08-21-2012, 06:31 PM   #5
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Something to think about is rigging up a temperature controller with a probe that hangs inside of the fermentation vessel. That way, the fridge kicks in if the actual fermentation starts getting warm.

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Old 08-21-2012, 07:04 PM   #6
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Like AmandaK said, 3-4 degrees is typical, but people have reported up to 10 deg difference. I'm not sure what data will do for you; it simply is what it is. And it depends on many factors, such as: (a) yeast strain, (b) fermentation temp targeted, (c) starter size, (d) OG, and (e) batch size.

Just a couple data points for ya: I recently saw consistent 3 deg difference on a 1.052 with Wyeast Kolsch at 60F, and just saw an 8 deg difference at peak fermentation (day 2) on a 1.072 pumpkin ale with Wyeast Amer. Ale II at 64F. I measure the wort with a lab thermometer and/or thermo strip, and for ambient I measure a glass of water next to the fermenter.

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Old 08-22-2012, 12:44 AM   #7
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As an aside, to monitor the wort temp, you don't need a thermowell. Just tape your probe to the fermentor, insulate it and go from there. You'll be within a degree or two that way.

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Old 08-22-2012, 04:26 PM   #8
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Or you can just submerge your fermenter in tub of water, and monitor temperature of surrounding water. You will MUCH closer to actual fermenting temperature that way.

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Old 08-22-2012, 05:06 PM   #9
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Quote:
Originally Posted by AmandaK
As an aside, to monitor the wort temp, you don't need a thermowell. Just tape your probe to the fermentor, insulate it and go from there. You'll be within a degree or two that way.
You use the set point of the thermostat to tell you the wort temp? I would definitely confirm the accuracy of this methodology first, because I could see having real error during the first couple days of fermentation.
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Old 08-22-2012, 05:57 PM   #10
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Quote:
Originally Posted by SpeedYellow View Post
You use the set point of the thermostat to tell you the wort temp? I would definitely confirm the accuracy of this methodology first, because I could see having real error during the first couple days of fermentation.
You think I haven't experimented with this. Teehee.

It was recommended by Jamil (I really hate dropping names, ugh) on one of the BN podcasts a few years back. Being curious, I took that information and applied it to my brewing. All of my fermenters have temp strips on them, and I tape the Ranco probe directly to the outside of the fermenter, tape a towel over it and use the Ranco to control the set point.

In my time using this system (probably about 30 something batches with the newest set up), my Ranco consistently reads 2 degrees higher than my temp strip. Is 2 degrees going to make or break my fermentation? No. But I do set the Rancos to 2 degrees lower than what I want the ferm temp to be.

Boom. Done. Over.
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On deck: German Pilsner, CAP, Golden Strong
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Souring: #32 Lambic 2.0, #49 Lambic 3.0, #60 3763 Flanders Brown, #61 WLP665 Flanders Brown
Conditioning: #38 Golden Sour, #58 Hooch Cider, #79 Dopplebock, #84 Amy Cider
Drinkin': #16 Lambic 1.0 (Drunk Monk BOS), #84 Fall Cider
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