Fermenting under pressure and kegging

[WinoBob]

Hi all,

So I'll be receiving my first FermZilla next week, and will be trying my hand at fermenting under pressure. I got the pressure kit for it, and also a Spundit valve. Just thought I'd outline my planned process here, and would love for you all to weigh in and punch holes in my logic, since I'm fairly new to kegging and the whole thought process when it comes to temperatures and psi.

Let's say I'm aiming for around 2.5 volumes of carbonation. Since the temperature where I keep the fermenter is around 65F, I thought I'd ferment the beer and set the Spundit at 29 psi. Then, a day or so before kegging, I'll purge the keg and put it in the fridge (which is at 40F) to pre-cool. When it's time to transfer, I'll pressurize the keg to 13 psi, connect the out post of the Fermzilla to the out post of the keg and let the difference in pressure push the beer over to the keg, and then put the keg in the fridge.

Does this make sense? Since I'm a bit of a noob, I may be all sorts of stupid here, so feel free to shoot me down!

Cheers!

 

[Jag75]

2.5 volumes @65 degrees is 26 psi. I've never attempted transferring carbonated beer yet . I would think your keg should be just under what pressure you have in your fermenter or else it will foam . I dknt know if 13 psi in a keg will work but I'm interested in this so I'll be watching. Someone with more knowledge will surely be here with advice . Congrats on your new Fv!

 

[burtom]

I would pressurize the keg to about 2 or 3 psi less the the fermenter and then use the sounding valve to allow gas to escape from the keg as beer is transferred. You can also hook CO2 up to the gas input of the fermenter, BUT BE SURE THE CO2 PRESSURE IS SET HIGHER THAN THE FERMENTER, just a bit. With the Fermzilla top draw system if you introduce a large pressure differential between the fermenter and the keg the hose on the beer out will probably collapse on it self and end no beer will flow.

 

[thunderwagn]

I've got the Fermzilla 7.1 gallon, pressure kit and Blowtie spunding valve. Here's what I've been doing with success. After transfer to the fermzilla, I let the trub settle to the bottom collection chamber and empty. That's an optional step but much easier to do now if you don't want to ferment with the trub as once you start fermenting under pressure it gets to be more of a messy process. Pitch my yeast, attach my pressure lid and set my Blowtie (spunding valve) to 15 psi. Initially your pressure will be absorbed but it will build up as fermentation takes off. Let fermentation complete. You can chill your keg and fermzilla at this point or just your keg (at least). Remove spunding valve from fermzilla and attach to keg gas side, purge air and pressure to 15ish. Liquid out fermzill to liquid in keg Start opening your spunding valve slowly till you get a fairly slow flow to the keg (about 2-3 psi less pressure in keg than fermenter). Take it pretty slow first quart or two to avoid foaming. You can slowly start opening your spunding valve a bit more. You may have to add pressure to the fermzilla periodically to keep things moving. I take it nice and slow. I'll easily take at least 45 minutes + for a transfer, but I'd rather take my time than deal with foam. Pop your keg in your cooling vessel and hook up the o2 to your typical pressure. If you aren't already chilled, I wait for a good 4-5 hours before trying a pour. You'll have carbonation, but I find it just about perfect the following day. Fermzilla is a great piece for the $$. Enjoy.

 

[Vale71]

If you want to avoid foaming you need to keep the pressure a bit higher than the spunding pressure in both vessels. You'll then need a spunding valve for the keg to set a slightly lower pressure than in the fermenter allowing for a gradual release of CO2 from the keg which will regulate the transfer speed.
If you pressurize the keg to half of the spunding pressure and then simply attach the lines beer will rush into the keg very fast and you're guaranteed excessive foaming. If you also don't attach a CO2 bottle to the fermenter, as you seem to imply when you say "let the difference in pressure push the beer over to the keg", pressure will drop quickly in the fermenter as well. The good news is this will slow down the transfer, the bad news is you'll most likely have foaming in the fermenter as well. Add to this that you plan to transfer your beer warm which makes everything worse foaming-wise and I doubt you'll manage to avoid a complete disaster.

 

[WinoBob]

I've got the Fermzilla 7.1 gallon, pressure kit and Blowtie spunding valve. Here's what I've been doing with success. After transfer to the fermzilla, I let the trub settle to the bottom collection chamber and empty. That's an optional step but much easier to do now if you don't want to ferment with the trub as once you start fermenting under pressure it gets to be more of a messy process. Pitch my yeast, attach my pressure lid and set my Blowtie (spunding valve) to 15 psi. Initially your pressure will be absorbed but it will build up as fermentation takes off. Let fermentation complete. You can chill your keg and fermzilla at this point or just your keg (at least). Remove spunding valve from fermzilla and attach to keg gas side, purge air and pressure to 15ish. Liquid out fermzill to liquid in keg Start opening your spunding valve slowly till you get a fairly slow flow to the keg (about 2-3 psi less pressure in keg than fermenter). Take it pretty slow first quart or two to avoid foaming. You can slowly start opening your spunding valve a bit more. You may have to add pressure to the fermzilla periodically to keep things moving. I take it nice and slow. I'll easily take at least 45 minutes + for a transfer, but I'd rather take my time than deal with foam. Pop your keg in your cooling vessel and hook up the o2 to your typical pressure. If you aren't already chilled, I wait for a good 4-5 hours before trying a pour. You'll have carbonation, but I find it just about perfect the following day. Fermzilla is a great piece for the $$. Enjoy.

This is invaluable, thanks!

 

[WinoBob]

Thanks all for the feedback. Being new to the whole kegging thing, I'm just trying to wrap my head around the science of temperature and pressure. Just for arguments sake, let's say I have a keg at room temperature and set the psi to achieve 2.5 volumes at that particular temperature, and let it sit for a couple of weeks. If I then put the keg in the fridge, do I adjust the pressure to the correct psi for 2.5 volumes at the fridge temperature?

And the other way around - if I have a keg in the fridge at 2.5 volumes and I then take it out of the fridge (don't know why I would do that, just trying to learn something here ), would I raise the pressure as the temperature rises?

Or to put it another way - even with a fully carbonated beer, you always adjust the pressure relative to temperature changes?

Thanks for your patience

Cheers!

 

[Vale71]

You might need to release some pressure when cooling the keg as with decreasing temperature the solubility of CO2 increases, so that some of the CO2 that was previously in the keg's headspace will move to the beer thus increasing carbonation. By how much depends on the headspace to liquid volume ratio. In any case you shouldn't adjust anything until the keg has been sitting at target temperature for at least several days as this is a slow process and being too rash in making adjustments can lead to ping-ponging effects.

When you warm up a keg some CO2 will move from the beer to the heaspace thus increasing pressure. Considering that you will eventually cool the keg again to serving temperature I would not release CO2 in this case as this will lead to permanently loosing some CO2 resulting in undercarbonation when the keg is cooled again, forcing you to then increase carbonation by means of force carbonation.

 

[WinoBob]

You might need to release some pressure when cooling the keg as with decreasing temperature the solubility of CO2 increases, so that some of the CO2 that was previously in the keg's headspace will move to the beer thus increasing carbonation. By how much depends on the headspace to liquid volume ratio. In any case you shouldn't adjust anything until the keg has been sitting at target temperature for at least several days as this is a slow process and being too rash in making adjustments can lead to ping-ponging effects.

When you warm up a keg some CO2 will move from the beer to the heaspace thus increasing pressure. Considering that you will eventually cool the keg again to serving temperature I would not release CO2 in this case as this will lead to permanently loosing some CO2 resulting in undercarbonation when the keg is cooled again, forcing you to then increase carbonation by means of force carbonation.

Again, invaluable insight. Thank you!

 

[DVCNick]

As a pressure transfer newbie (hopefully will be doing my first one in a couple weeks) what is the major downside to foaming in the closed system? Gumming up your spunding valve on the keg side?

 

[hopjuice_71]

When I started spunding I tried warm transfers of carbonated beer in all sorts of configurations. It was always a mess with the foaming. Now I crash the spunded vessel (kegs for me) to near freezing and transfers are straightforward with little need for special attention to foaming.

 

[Qhrumphf]

Another method, if possible, is to use a balance line. Get your keg close to the same pressure as your fermenter, and then gas out from the keg connects to gas in to your fermenter. Then you could free flow by gravity, or use a sanitary pump (a diaphragm pump works well for this).

 

[DVCNick]

I'm about 48 hours into this fermentation and I think it has peaked with a normal airlock. Just now I dropped on the pressure kit and set it up to liquid purge a keg using fermentation gas. I hope this doesn't build enough pressure to reduce ester production in this particular beer. Any thoughts? The liquid out on the keg is just open in the bucket.

 

[Jag75]

I think it's a good idea. Saves Co2 . If it can push it all out that's cool . You could even jump it to another keg .