Multiple carboys in fermenting chamber

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Joon1975

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I have a 7.0 cubic freezer as a fermenting chamber. Can I ferment two carboys at the same time? Being different beers. I have one temperature control. Thanks!
 

RM-MN

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Same starting date or different? Your beer really only needs active cooling while it is in the early stages of fermenting. By day 3 or 4 you can let it warm to room temp with no problem as the fermentation where the off flavors is produced is over (big beer exceptin, they take longer). As long as you are brewing them a few days apart you can do as many brews as you want.
 
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Joon1975

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Sure, as long as they both are supposed to ferment at the same temps. If not, then you'll have to plan on doing two similar ferm temp brews together.
Yes, I would ferment at the same temp.
 
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Joon1975

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Same starting date or different? Your beer really only needs active cooling while it is in the early stages of fermenting. By day 3 or 4 you can let it warm to room temp with no problem as the fermentation where the off flavors is produced is over (big beer exceptin, they take longer). As long as you are brewing them a few days apart you can do as many brews as you want.
Different dates, I’m thinking from weekend to weekend. I usually ferment for three weeks. I was thinking having the probe attached to the first beer and then switch it to second beer a week later.
 

kh54s10

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If I brew a week apart, I figure the first one is pretty much done so I set the temperature for the new batch, or take the first one out and let it go a little longer at room temperature. I also have a large fermentation chamber and have had 3 at once in there a couple of times.
 

kh54s10

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Yes, make sure you have the temperature probe on the new batch. You want to control it's fermentation temperature. The temperature on the older batch would be stable.
 

mongoose33

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There are several factors in whether that will work well or not. The vigor of the fermentation of one or the other batch is one consideration. Another is the recipes--might work with a couple of ales, not so much with one ale and one lager.

It's easier to do this with two Inkbirds and two heat mats to add heat to each fermenter as needed. The issue is that fermenting yeast is exothermic, i.e., adds heat to the fermenter. From 5-10 degrees over ambient unless you control ferm temp; I'm sure you know this, but it helps understand the next part.

Let's say two batches. Batch one starts out and maintains 65 degrees, all is well. Three days later the fermentation slows, and you add your second batch to the freezer. You control the freezer with the temp of the second batch which, of course, has a lot of yeast activity--heat generation!--going on. So the freezer is on a lot to control that.

Problem is, Batch 1 isn't producing much heat, so the cooling of Batch 2 sends the temp of Batch 1 down below the 65 degrees.

I like to raise the temp of my beers at the end to allow the yeast to clean up after themselves. This would be impossible with the above approach, and I'd expect Batch 1 to end up down around 60 degrees.

Now, if you're OK with that, it is of course fine.

Here's a thread I did a while ago describing how I do two batches in the same fermenter. Unless they're the same recipes at the same time, you have to stagger them. If you don't have two Inkbirds (you have one, but they go on sale all the time), and two heat mats, it's moot.

Or, it might give you some other idea on how to best do this given your equipment and circumstances.

https://www.homebrewtalk.com/forum/threads/two-fermentations-one-ferm-chamber-it-can-be-done.631776/
 

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