CRASH COOLING SUCK BACK ISSUES SOLVED. C02 Reservoir for your fermenters

[doug293cz]

New to the cold crash idea and plan on using it in the future, glad I found this but I do have a couple questions to make sure I understand. Does the first jar, connected directly to the fermenter, get filled almost completely with sanitized fluid to limit the amount of air in the jar? In the video there is only fluid placed in the second jar. In this scenario the first jar is 100% air and contains oxygen, which we do not want. As CO2 is pushed into the first jar during fermentation it will sink as it is denser than air and then be pushed right out into the second jar. During cold crashing the first gas to be pulled back in would be the air sitting atop the CO2 in the second jar, wouldn't it?

I would think that a better method would be to have two large jars, no liquid. Still using the provided lids on the first jar have the tube from fermenter go in and on the same connection have the dip tube effectively pushing CO2 into the bottom of the jar and pushing the air out of the outlet into the second jar, do the same on the second jar with the dip tube being on the inlet. Again as the first jar fills with CO2 it will push air through the second jar until it too begins to fill with CO2 while pushing air through the air lock on the lid. As long as the dip tube in the second jar is short enough to not pull in the water from the s lock off the bottom of the jar during crashing you should reclaim mostly CO2. Am I overthinking this?

The CO2 does not sink to the bottom of the jar. CO2 mixes with the air completely in a matter of minutes. Doesn't matter much if you start with liquid in the first jar or second jar, as it will all end up in the second jar shortly after the fermentation begins. There is enough CO2 pushed out of the fermenter to dilute the O2 concentration in the jars down to single digit ppb levels.

The purpose of the liquid in the jars is to minimize air suck back when cooling. The S lock alone will not prevent air suck back. You need more liquid in the second jar (at the end of fermentation) than the volume of air that will be sucked back during cooling. Otherwise you will eventually suck back air into the fermenter.

For more information read and study my posts earlier in this thread, and the posts linked in the earlier posts.

Brew on

 

[homebrwd]

The CO2 does not sink to the bottom of the jar. CO2 mixes with the air completely in a matter of minutes. Doesn't matter much if you start with liquid in the first jar or second jar, as it will all end up in the second jar shortly after the fermentation begins. There is enough CO2 pushed out of the fermenter to dilute the O2 concentration in the jars down to single digit ppb levels.

The purpose of the liquid in the jars is to minimize air suck back when cooling. The S lock alone will not prevent air suck back. You need more liquid in the second jar (at the end of fermentation) than the volume of air that will be sucked back during cooling. Otherwise you will eventually suck back air into the fermenter.

For more information read and study my posts earlier in this thread, and the posts linked in the earlier posts.

Brew on

Thank you!

 

[Murphys_Law]

Thinking of pulling the trigger on this...how is it working out for everyone?

 

[homebrwd]

Just snagged one of these, thank you Jay for the quick chat on the phone!

 

[Jaybird]

Just snagged one of these, thank you Jay for the quick chat on the phone!

Absolutely my pleasure! I have alerted my shipping team to look out for the custom notes! You're all set up!

Cheers
Jay

 

[homebrwd]

Absolutely my pleasure! I have alerted my shipping team to look out for the custom notes! You're all set up!

Cheers
Jay

Got it all set up today, thanks again!

 

[Inkleg]

Going to use my setup today for the first time. Thanks Jay!

 

[Jaybird]

Got it all set up today, thanks again!

WOW That got there FAST! You sure didn't mess around getting it put together and in use!

Cheers
Jay

 

[Jaybird]

Got it all set up today, thanks again!

Going to use my setup today for the first time. Thanks Jay!

You bet!

Let me know how you like it!

Cheers
Jay

 

[chordwizard]

So nobody has weighed in on whether or not they think the airlock is really necessary or not? I'm thinking that if the 2nd container is full of starsan that the fermentation gasses purge the first container and bubble up through the 2nd. When you crash cool as much of the liquid as is need is sucked back into the first container. The airlock would vent the excess CO2 from the small space above the liquid during fermentaion but would not stop air from going back into the 2nd container when cooling. Am I missing something?

 

[doug293cz]

So nobody has weighed in on whether or not they think the airlock is really necessary or not? I'm thinking that if the 2nd container is full of starsan that the fermentation gasses purge the first container and bubble up through the 2nd. When you crash cool as much of the liquid as is need is sucked back into the first container. The airlock would vent the excess CO2 from the small space above the liquid during fermentaion but would not stop air from going back into the 2nd container when cooling. Am I missing something?

I don't think you're missing anything.

Brew on

 

[Jaybird]

So nobody has weighed in on whether or not they think the airlock is really necessary or not? I'm thinking that if the 2nd container is full of starsan that the fermentation gasses purge the first container and bubble up through the 2nd. When you crash cool as much of the liquid as is need is sucked back into the first container. The airlock would vent the excess CO2 from the small space above the liquid during fermentaion but would not stop air from going back into the 2nd container when cooling. Am I missing something?

I don't think you're missing anything.

Brew on

Nope not missing anything at all. You can choose to use an airlock or not. We have people ONLY using the second jar for a blow off so we decided to add the airlock for them mostly. I personally use the airlock and fill it with a neutral spirit to sanitize the air coming back into the system. But that's is just me and probably way overkill! Besides that I really like the smell as the ferment Co2 is passing through the neutral.

Cheers
Jay

 

[Inkleg]

I like the way this set up works. My first attempt using it it would not push sanatizer from jar one to jar two, I suspect air leak. Second attempt I purged jar one with co2 with no liquid in it and it worked great.......well except that I was doing a Belgian with Wyeast 3787. It filled jar one with blow off and then pushed that into jar two. I forgot what a beast that yeast is. After some clean up as high krausen started to fall it worked fantastic!!
I'm sure this picture will post sideways as I'm an idiot.

 

[ba-brewer]

With 1.5 gal (5.7 L) of headspace, I get your suck-back due to CO2 thermal expansion as 0.1 gal. You should see this as soon as the fermenter is down to crash temp (maybe even sooner due to the beer absorption.) However, as the CO2 level in the beer at crash temp comes to equilibrium with the CO2 in the headspace, you will get an additional suck-back of 3.4 gal (unless you start sucking back air, which will reduce the CO2 partial pressure.) To get this much total suck-back will probably take two weeks or more, but since absorption is fastest at the beginning of the process, it might only take a day or two to suck-back more than 1/2 gallon.

You should be using more sanitizer in your jar. Once the sanitizer in the last jar sucks back into the first jar, you start sucking air back as well as whatever CO2 is left in the jars. You want to start with the sanitizer in the first jar, and it should be filled to about 1/4" below the bottom of the nipple connected to the fermenter.

Then when you cold crash, you should keg the beer as soon as the sanitizer in the second jar is almost all sucked back to the first jar, if you want to avoid all air suck-back. Or, if you have the capability, you could blow CO2 into the fermenter until the sanitizer is all back in the second jar. Rinse and repeat as necessary to complete your desired cold crash time.

Brew on

Have you used your setup yet and does it work to your calculations?

Question for the people who are using this setup for 5 gal batches in a 7gal fermentor.
Does the two 1/2gal jar configuration provide enough reserve to crash from the mid 60s to the upper 30s for 2 or 3 days?

 

[doug293cz]

Have you used your setup yet and does it work to your calculations?

Question for the people who are using this setup for 5 gal batches in a 7gal fermentor.
Does the two 1/2gal jar configuration provide enough reserve to crash from the mid 60s to the upper 30s for 2 or 3 days?

I haven't brewed for a while, so no data to share. I know there are others using that configuration tho.

Brew on

 

[55x11]

Have you used your setup yet and does it work to your calculations?

Question for the people who are using this setup for 5 gal batches in a 7gal fermentor.
Does the two 1/2gal jar configuration provide enough reserve to crash from the mid 60s to the upper 30s for 2 or 3 days?

Yes it will work fine. I use the same setup.

You will get about 7% change in volume from headspace from 70 to 30F.
So with 2 Gal of headspace, thats about 0.14 gal. You should be fine. See calculation Doug made.

The CO2 adsorption is important, but it takes time to adsorb CO2, as we all know. The set-and-forget methods take many days to reach equilibrium. Again, see Doug's calculation above. If you are concerned about CO2 re-adsorption, you can always cold-crash faster.

One minor correction - even if headspace is zero and we neglect CO2 adsorption, the liquid (beer) itself shrinks too. It's only about 0.2% from 70F to 32F, so a small fraction of what normal headspace would do, but keep that in mind - eliminating headspace entirely does not save you.

Incidentally, for CO2 reabsorbing back into the liquid, you want larger headspace as well.

 

[ba-brewer]

I haven't brewed for a while, so no data to share. I know there are others using that configuration tho.

Brew on

Thanks Doug.

Yes it will work fine. I use the same setup.

You will get about 7% change in volume from headspace from 70 to 30F.
So with 2 Gal of headspace, thats about 0.14 gal. You should be fine. See calculation Doug made.

The CO2 adsorption is important, but it takes time to adsorb CO2, as we all know. The set-and-forget methods take many days to reach equilibrium. Again, see Doug's calculation above. If you are concerned about CO2 re-adsorption, you can always cold-crash faster.

One minor correction - even if headspace is zero and we neglect CO2 adsorption, the liquid (beer) itself shrinks too. It's only about 0.2% from 70F to 32F, so a small fraction of what normal headspace would do, but keep that in mind - eliminating headspace entirely does not save you.

Incidentally, for CO2 reabsorbing back into the liquid, you want larger headspace as well.

I did see doug's calculation and the large volume of co2 at equilibrium seems a bit concerning, that is why I am looking for real world observations.

​

 

[peoples22]

I appreciate everyone's feedback and discussion in general on this topic. Got mine ordered today!