Multiple Fermentations...at once

[dammBrewer]

Just wondering everyone's thoughts on this idea.

I am going to re-purpose a full size fridge that I have at home. In doing so, I was thinking about building in a shelf system that should allow me to ferment at least 4 6 gallon carboys at once. My concern is temp control.

I was wondering if someone has an idea on how to best manage/maintain/monitor the temps in each carboy? I am well versed in the aspect of using Inkbird, or STC or whatever brand you want; but, all those only have 1 temp probe. Now, if I tape/stick that to the side of carboy 1, how do I know carboys 2,3 and 4 are around/at the same relative temp?

Or do I take the approach to put the probe in a soda bottle of water and put that in a centrally located area of the fridge and hope that the carboys all maintain based on that? Or better yet, can multiple probes be used with 1 system and attached to each carboy?

Visuals help if someone has done this but thoughts and ideas are always welcome too. Thanks in advance guys and gals....

 

[BigMack]

I would think you would just have to maintain the ambient temp with a bottle of water like you mentioned. I don't think you could use multiple probes as they would all be reading different temps and the controller couldn't magically make all of them exactly the same if they are at different stages of fermentation.

I would also worry if you just had it on one carboy that if that had vigorous fermentation then it may cause the ambient temp in the fridge to drop too low for a beer that needs to finish out the end of its fermentation.

I think getting the ambient temp to about 66 would likely be your best bet.

 

[kombat]

Now, if I tape/stick that to the side of carboy 1, how do I know carboys 2,3 and 4 are around/at the same relative temp?

You don't.

The ideal solution is to only ferment one beer at a time, and measure the temperature with a thermowell. If you insist on fermenting multiple beers simultaneously, then I would just let the probe dangle in the air, and maintain an ambient temperature a couple of degrees cooler than the desired fermentation temperature (say, 62° F).

Or do I take the approach to put the probe in a soda bottle of water and put that in a centrally located area of the fridge and hope that the carboys all maintain based on that?

Nope, that's the worst possible solution.

Here's why: Think about what happens during fermentation. You've got your fermenter sitting in the fridge, and the beer is at exactly the right temperature. The yeast start working, producing heat. The beer warms up a little bit. If you had the probe inside a thermowell, then the temperature controller would know immediately, and could turn on the fridge to keep the temperature where it's supposed to be.

But your probe isn't in a thermowell. It's in a bottle of water, which hasn't changed temperature (because there are no yeast in it producing heat). So the beer warms up. This warms up the surrounding air in the fermentation chamber. If your temperature probe were dangling loose, this is the point at which it would notice an increase in temperature, and could turn on the fridge to cool things back down.

But your probe isn't dangling loose. It's still in that bottle of water. Now that the surrounding air has started warming up, the water in the bottle finally also starts warming up. Meanwhile, the temperature of your beer is spiking, because the yeast are getting more and more excited, and the temperature controller still hasn't yet turned on the fridge to cool things down.

Finally, the temperature of the water in the bottle increases by enough to trigger the temperature controller to activate the fridge. But by now, who knows how warm your beer has gotten in the meantime.

Now, a similar problem occurs while cooling down. The temperature controller notices that your bottle of water has warmed up a little, so it turns on the fridge. The fridge cools the air down, which slowly cools down the water in your bottle. It cools the beer down a little bit too, but not as much, since it a) has more thermal mass, and b) has active yeast in it producing heat. Before too long, the water in the bottle has cooled back down to the target temperature, so the temperature controller kills the power to the fridge. But the beer is still too warm. The air inside the fridge will be considerably cooler than the water in the bottle, so the water in the bottle might continue to cool for a while, before bottoming out and starting to warm up again. During this whole time, the beer is still above the target temperature, and getting hotter again.

As you can see, this is a terrible solution. Best idea, probe in thermowell in beer, second-best idea, tape probe to the outside of the fermenter and cover it with some sort of insulator (foam, bubble wrap, whatever), third best is to just let the probe dangle freely in the air. But immersing it in a separate liquid is the worst possible solution.

 

[m1k3]

Temp control is most needed in the first few days to about a week of fermentation.

Personally I would prefer to temp control 1 batch at a time... then move the fermenter out of the chamber to a second location.

Looks like you live in Wisconsin... so, when it is cooler part of the year you can use a ferm wrap or brew belt heater only to temp control the fermenter when it comes out of the ferm chamber. (garage, basement or cool part of the house will work).

After that you can return the fermenter to fridge to cold crash... or take it off temp control for longer bulk aging.

 

[m1k3]

I agree with kombat.

Best solution is a thermowell or probe taped to the fermenter and insulated.

This can be done with the active fermentation in the chamber and any other fermentation in a cool enough area using heat only control.

 

[BrotherBock]

Or do I take the approach to put the probe in a soda bottle of water and put that in a centrally located area of the fridge and hope that the carboys all maintain based on that?

I would advise against this method. My brew buddies do this and while I think it may give you a relatively accurate reading of the temp in the fermentation chamber as whole it is worthless for telling you the temp of the wort (at least during fermentation).

Probe in a thermowell or taped to the side of a carboy is going to be a much more accurate way to measure the temp of the fermenting wort IMO. I never understood the logic of using a cup of water. Their super fruity and unkolsch-like Kolsch is enough evidence for me to never use that method.

 

[m00ps]

Like kombat articulated, using a bottle of water as a means to maintain a "stable" temperature will work...for that bottle of water. But thats not what you wnat. You want to maintain the beer. Even a temp probe taped to the side of your fermentor will do a better job of this, but not for the fermentors it isnt taped to

Unless you have a divided fridge with, multiple temperature probes, and a different coolant system for each division, I see one less than elegant solution.

It all depends on how often or how many batches you are having fermenting at once. As well as what types of beer you are making. Some beers (belgians) you can pretty much get by with zero temperature regulation so long as your house is around 70F. Lagers and Ales will not mix well in the same temp environment except for special strain or if the lager is pretty much done fermenting

So, I have room for 2 in my chest freezer and usualyl have 1-2 beers in it. I usually keep it at like 60-62 since it has a temp probe taped outside the fermentor (one of them). I estimate the actual temp during active fermentation to be in the mid 60s (of the one its taped to). So I will have the temp probe taped to the newest beer in there since it will be more subject to temperature fluctuations. After a week or so, I will take one out if I need to in order to make room. Its not ideal, but the impact from moving a beer from the 60s to room temp after active fermentation has stopped is pretty minimal. And, as I said before, styles such as belgians dont go in there so I plan my brewing schedule around that. Nothing goes straight from the chest freezer to kegging or packaging. Its good to let them sit at room temp for a couple days for the yeast to finish up

 

[balrog]

There's also the method of fermenting N beers in a chest freezer with N fermwraps and N+1 temp controllers -- one controller to keep freezer at a constant cool temp, and N controllers on each fermwrap on the individual N beers.

 

[BeardedBrews]

If you have more than one thing to control at the same time, then you either need more than one single sensor controller (Inkbirds) or you need a multiple sensor controller (BrewPI).

@Huaco did a nice write-up of a 3x STC chamber here:
https://www.homebrewtalk.com/showthread.php?t=372521

The concept is that you use the controller for the coldest carboy to drive the freezer, and then the other two simply heat their carboys up to their desired temperature. Adding insulation around the "warm" carboys will probably help stabilize them.

 

[Huaco]

If you have more than one thing to control at the same time, then you either need more than one single sensor controller (Inkbirds) or you need a multiple sensor controller (BrewPI).

@Huaco did a nice write-up of a 3x STC chamber here:
https://www.homebrewtalk.com/showthread.php?t=372521

The concept is that you use the controller for the coldest carboy to drive the freezer, and then the other two simply heat their carboys up to their desired temperature. Adding insulation around the "warm" carboys will probably help stabilize them.

Thanks for the mention... I need to break out the multi controller again and utilize it more. I don't know that I would recommend lagering while fermenting Ale as I did in my test, but it did "work". In hind-sight I think that was just too much Delta. although, the idea of insulating the warm fermentors is a nice idea to test. It wouldn't have any problem controlling say a low-slow fermentation in the low 60's while another beer, say a big banana-ester filled Weizen ferments at 72 or a Belgian, even hotter.

 

[BeardedBrews]

I need to break out the multi controller again and utilize it more.

If it's gathering dust I'd happily give it a new home for you

I've got a pair of STCs now and am avoiding the chore of building a box to house them. As it stands, one of them is wired up inside of the Amazon cardboard box that it showed up in!

-B

 

[dammBrewer]

Huaco has a great idea here. Honestly, I do remember hearing about it but couldn't place it.

I understand the water bottle idea is not going to work. Sorry to bring that up; my bad. I use that for my kegerator and it works...that must have been my train of thought and I didn't catch it before I submitted. My bad. Not using it. Moving on. LOL.

I am going to look into the idea of building a 3 stage like @Huaco did. I am going to only do ale's with ales' and lager's with lager's though.

My main concern here and the single most reason I brought this up in the first place is that my batch sizes are going to be larger this year than in the past. I want to do 10-14 gallon batches and have to split them as my carboys are 6 gallons each. So putting a few in there at once, same wort, maybe different but similar yeast, is what I want to achieve control over.

Thanks again everyone. I knew putting this out there would get responses, you are all awesome!