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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > How much temp oscillation is ok?
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Old 05-17-2012, 10:20 PM   #1
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Default How much temp oscillation is ok?

Right now I'm fermenting in a freezer with a dual stage temp controller. I'm using a brew belt as a heat source. The temperature probe is taped and insulated to the carboy.

I have my temp controller set at 19.5 C with a 0.3 C differential and a 10 minute short cycle delay.

I'm seeing a swing of 19.8 to 19.1 over a 30 minute period. Starting at 19.5 the brew warms up to 19.8 where the freezer comes on. The temp drops down to 19.5 and the freezer shuts off. The temp continues to fall and when it hits 19.2 the brew belt comes on. The temp dips down to 19.1 before it starts back up and the belt shuts off at 19.5. Then it repeats. The whole process takes just less than half an hour.

Do you think this swing is a problem or is the temp averaging out in the fermenter so that the yeast don't see quite as much of a swing?

The freezer and the belt don't run very long at each stage. Just a few minutes each.

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Old 05-18-2012, 02:53 AM   #2
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The temp will be averaging out a bit in the barrel.

To be honest, less than a degree variation seems incredibly small to me, even if it's within a half hour window. It's kind of impressive that you've gone to this much effort. I don't have a control to compare it too but most homebrew I've tasted varies by several degrees throughout the day and still seems to taste pretty good.

How long does attenuation usually take in this set up?
Do the yeast seem distressed?
Any off flavours?

If this is the first batch you've done, then the questions would be
How quickly are the yeast fermenting sugar (points/day?)
Do the yeast seem distressed?
Any off flavours yet?

I guess it depends what you're asking. The more constant the temp the better quality the brew. That said, I've had brews that have varied by several degrees each day because of the ambient temp.
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