Pressurized Closed Loop Corny Keg Fermenting

[schematix]

My question is if blow off gets into the SK, what do you do about it? Just leave it?

I usually backflow it... just blip the FV PRV a little bit and it'll suck it right back to the main. Still closed loop.

 

[SanPancho]

two Qs about process and then one general Q-

so when we are talking about adding sugar/finings/etc to the keg, and going through the PRV hole with a funnel- is there an easy way/trick to do this? or just wrench the PRV out and then quickly screw it back once done? some positive co2 pressure?

and no need for CBC or F2, we are just using the main yeast for carbing?

lastly-

in the event that i have a lager and ale going at same time in same cooler, are the typical 40w fermwraps powerful enough to keep the ale in the upper 60s if the cooler ambient is only low to mid 50s for the lager? i assume i'd need to insulate the ale with reflectix, neoprene, etc. over the fermwrap, but wondering if thats enough or should i try a heating pad with more power. i have the heating pad already, would have to buy the fermwrap.....

 

[schematix]

so when we are talking about adding sugar/finings/etc to the keg, and going through the PRV hole with a funnel- is there an easy way/trick to do this? or just wrench the PRV out and then quickly screw it back once done? some positive co2 pressure?

and no need for CBC or F2, we are just using the main yeast for carbing?

I hook up co2 at a pressure of about 5 psi for positive pressure. I then use a large 100mL syringe to inject the solution. The PRV can be unscrewed with your fingers, definitely don’t wrench it.

And the yeast in the keg is enough. No additional bottling yeast needed.

 

[daveMN]

I'm finally getting around to setting this up and have a couple of questions:
1. When you water purge your kegs, do you deaerate or scavenge the water first? There isn't much left in the keg, granted, but it seems like a potential oxygen source. I've been using StarSan for my keg purges.
2. My fermentation chamber isn't big enough for two kegs, so before I drill a hole through the side of it, what pressure should I have the SK set to, given the different volume and temperature compared to the FV headspace and lower fermentation temp?
Thanks!

 

[schematix]

I'm finally getting around to setting this up and have a couple of questions:
1. When you water purge your kegs, do you deaerate or scavenge the water first? There isn't much left in the keg, granted, but it seems like a potential oxygen source. I've been using StarSan for my keg purges.

Very good point. I probably should, but i don't. Boiling that much water is just way too much time/effort/energy, even for me. I also spund so i get active scavenging, which is perfect for that.

I have recently considered is adding sulfites to the water. I just need to calculate how much and i'll probably do it next time or two.

2. My fermentation chamber isn't big enough for two kegs, so before I drill a hole through the side of it, what pressure should I have the SK set to, given the different volume and temperature compared to the FV headspace and lower fermentation temp?
Thanks!

I'd probably do the same "few psi". Once you rack to the SK and spund that keg then i'd go by the standard co2 volumes/temperature/pressure charts.

 

[daveMN]

Thanks! That was easy! Just need one of those cool thermowell corny lids. :beer:

View attachment 1510627368827.jpg

 

[cheesebach]

Thanks! That was easy! Just need one of those cool thermowell corny lids. :beer:

Just to get a better reading of the liquid temp? I think a nice bonus of fermenting in a keg (or any stainless fermenter) vs. a plastic fermenter is that you can get an accurate reading of the liquid temp externally for free since steel is a much better conductor of heat than plastic. I just put a blob of plumbers putty to shield the temperature probe from the ambient air, and if there is any difference between the actual temp of the liquid and what the probe reads, it’s a couple tenths of a degree at most.

 

[schematix]

I just put a blob of plumbers putty to shield the temperature probe from the ambient air, and if there is any difference between the actual temp of the liquid and what the probe reads, it’s a couple tenths of a degree at most.

When i tried to insulate the probe on the outside of the keg it was a couple degrees different than the thermowell probe registered. It was warmer in the thermowell than the external probe registered. Greatest difference was during peak fermentation and got lesser as fermentation progressed.

Better than nothing for sure, but it's much more stable in the thermowell. Consequently the compressor cycles less too.

 

[cheesebach]

When i tried to insulate the probe on the outside of the keg it was a couple degrees different than the thermowell probe registered. It was warmer in the thermowell than the external probe registered. Greatest difference was during peak fermentation and got lesser as fermentation progressed.



Better than nothing for sure, but it's much more stable in the thermowell. Consequently the compressor cycles less too.

Using bubble wrap or something like plumbers putty? I’ve been skeptical of how good a job bubble wrap can do unless its taped up really well to seal in the probe from any outside air. With a big blob of putty on the side (facing away from the walls of the freezer), I’ve had to lower my hysteresis down to 0.2F, or my compressor isn’t even coming on once an hour during fermentation. Even at 0.2F, it takes a good 10-15 minutes of run time to come back down to target and another 30-60 minutes to rise back up. With my plastic Speidel, hysteresis is usually set to 1F, and this still seems to cycle more often than 0.2F with the keg.

 

[Bigdaddyale]

sub

 

[schematix]

Filled lager fermenter. Removed gas posts and installed blow off. Working well. Don’t be scared to fill these up when doing lagers and using a blow off early.


View attachment 420599

I pitched another 500mL of yeast to this too.

 

[daveMN]

I think I just learned that a spund valve is key to this process. And I don't think I put enough Fermcap in the FV keg. Luckily I have a couple extra fully purged kegs handy. And yes, a spund valve is my next purchase!

 

[schematix]

Yah spunding is one of the most highly underrated processes in home brewing. So many advantages.

I'm becoming less of a fan of it early in fermentation though. I find it easier just to blow off and once things calm down, then spund.

 

[Sadu]

Spunding is awesome. Does great things for lagers IMO and I love using the fermentation gas to purge the keg properly and for free. I brew up to 32L in a 35L vessel and have been starting off at 5psi to compact the krauesen, otherwise blowoffs happen. What are your thoughts against using mild pressure at the start of fermentation?

 

[daveMN]

Yah spunding is one of the most highly underrated processes in home brewing. So many advantages.

I'm becoming less of a fan of it early in fermentation though. I find it easier just to blow off and once things calm down, then spund.

I'm still impressed with how much CO2 fermentation kicks out. A bubbling airlock doesn't show it like a climbing pressure gauge.

I'm thinking about putting two kegs in series, the first one to catch the blow off, and spund with the second. What's one more keg to clean, right?

 

[schematix]

What are your thoughts against using mild pressure at the start of fermentation?

The only reason I have recently stopped doing pressure early in the ferment is that i've been traveling a lot M-F, and i'm terrified of leaving something like that unattended. With a blow off tube i know when i come back a few days later that it'll then be time to spund and start building pressure. That coupled with the fact i've been filling the kegs more and more full each time increases the risk of a clog in the gas QD and a big mess.

I'm thinking about putting two kegs in series, the first one to catch the blow off, and spund with the second. What's one more keg to clean, right?

Probably easier and cheaper to get something like a filter housing.

 

[Sadu]

@schematix (sorry having trouble figuring out this new quoting thing)

I gather you are using a spunding / aka variable pressure relief valve on your empty keg, but you are saying that if the gas line in the fermenting keg gets blocked you end up with potential for 100 psi and at best a wrecked batch?

That's something I haven't considered. I have a bit more headspace in my fermentor, and the pressure works to keep the head nice and small.

 

[schematix]

but you are saying that if the gas line in the fermenting keg gets blocked you end up with potential for 100 psi and at best a wrecked batch?

My concern lies more in the gas post poppet and the QD poppet than in the keg itself. Those pieces have very small cross section and they are also not smooth, so are just asking for something to get stuck. I really try to max out the keg volume (i'm currently going above the top weld by about 1/2" so it's virtually guaranteed something is going to come out the gas port.

In a perfect world i'd have more head space and i'd just let it stay pressurized the whole time. But for right now i'm just throwing a blow off tube on for a few days, then once the highly active fermentation is done, i snap on the adjustable pressure relieve valve.

 

[stonebrewer]

Time for a dumb idea...feel free to tell me what I am missing:

Setup - I have a Zymatic, so I do smaller 3 gallon batches. Keep that in mind. Means a lot more headspace in the keg and thus a lot more oxygen, so I have to purge the kegs of O2 or the batches get brown in a week or less. I ferment under pressure with a spunding valve and have regularly kept it set at 20 PSI without any issues. Fermentation is usually done in about a week. I have a clear draught system in my serving keg with a stainless screen I designed/built over the intake.

Here's the idea - instead of (or in addition too?) water purging the serving vessel, why not just push a half gallon or so over from the FV while at peak fermentation? Yeast move over with some wort, eat all the O2, and Bob's your uncle? I am a firm believer of the KISS principle (yeah, even though I am a DIY homebrewer!) and it seems to me that this might work well. What am I missing here? Could even work for the times when I use my larger system for 5 or 10 gallon batches.

 

[schematix]

Time for a dumb idea...feel free to tell me what I am missing:

Here's the idea - instead of (or in addition too?) water purging the serving vessel, why not just push a half gallon or so over from the FV while at peak fermentation? Yeast move over with some wort, eat all the O2, and Bob's your uncle? I am a firm believer of the KISS principle (yeah, even though I am a DIY homebrewer!) and it seems to me that this might work well. What am I missing here? Could even work for the times when I use my larger system for 5 or 10 gallon batches.

You are thinking in the right direction!

Perhaps here's an easier way to execute though:

1. Water purge serving keg.
2. Ferment as usual in standard corny fermentation vessel, using whatever pressure you like and have success with.
3. When you are about 4 gravity points above final gravity, rack to the serving keg using the closed loop transferring method, being sure to CO2 purge all your lines. To do this you'll need to perform a force ferment test.

a. To do the FFT, when you see signs of fermentation (lots of gas), pull a sample through the liquid dip tube, approx 150mL, into a container. Put this in a warm place on a stir plate and let it run to FG. This should ideally finish before the main batch. You want to rack roughly 4 gravity points above FG, so monitor your main batch.​

4. Seal the serving keg and allow to come to desired pressure/carbation level. Attach spund valve if pressure is too high.

The yeast still being active when you rack is your protection against oxygen in the second keg. If you miss the window to rack at FG+4, don't worry. Make up a small amount of priming solution, roughly 2:1 by weight of water to sugar, boil it, and inject it through the FV keg's prv while you are applyign gas pressure to the gas side. If you do this with a day or two of reaching final gravity it'll start bubbling away within the hour. Then rack it.

It's a bit of a pain if you miss the window but i've had great success with priming that way. The key is to get it out of primary the moment its ready.... no 28 days on the cake! You're looking at 2-5 days for ales and 5-10 days for lagers depending upon some other variables.

 

[stonebrewer]

@schematix : I hear ya and I understand how others are doing this. To be frank, I am busy/lazy and want to find a few shortcuts to cold side LODO without giving up the benefits. I don't want to water purge the keg if I can let the yeast just eat the O2 up. I don't want to monitor the fermentation. I want to brew great beer and drink it with as little effort as possible, without skipping necessary steps. Seems to me you are onto something with your approach above...i.e. it is a pretty sure bet that your method will eliminate O2 contamination. I want to do the same, but eliminate some of the effort, if possible. Seems to me that if you skipped 1-4 and just move the beer to the SK over while still fermenting (either a little or all of it), it would take care of O2 issue we are all trying to avoid. Am I missing something or is your method being super cautious and conservative? Bottom line is I am going to try both methods and see if I detect any differences...should be a fun experiment! Cheers!

 

[schematix]

I wish all of this were easier. However, I have no reason to believe that this is super cautious, or conservative - it's just the way it is. Feel free to try cutting some corners though and see how you do. It does get easier and quicker the more you do it.

I think the issue with having a headspace full of O2 is that the yeast can't eat it unless it's in solution. So some will diffuse into the beer and the yeast will consume it while the yeast is active, but some will also stay in the headspace and eventually the yeast will go dormat before all has been consumed. And then oxidation sets in.

All i can say is that the more stringent my process, the better the beer got. But that's not to say there's not another way to skin this cat though that's easier.

 

[cheesebach]

I can understand the need for the full water purge of the serving keg if you’re going for the full LoDO process, and you’re trying to preserve the so called delicate malt flavors that are hypersensitive to oxygen. However, I don’t see any reason that adapting the method of purging the serving keg using the CO2 produced by fermentation couldn’t be utilized on its own to provide a better/easier/cheaper method of getting beer transferred to a CO2 purged keg on it own. Compared to the standard homebrewer practice of racking beer through a siphon to the bottom of a regular purged (or not purged) keg and then purging the headspace after transfer, following this process without water purging the serving keg would probably still be an order or magnitude better in terms of O2 exposure. Plus, you’d be saving on CO2 if that matters to you. The volume of CO2 produced by fermentation is probably around 30X the volume of a keg, and you’re bringing in the heavier CO2 from the bottom and pushing the lighter O2 out the top the entire time, which should result in very low O2 by the end.

No, it’s not as good and probably not LoDO-compliant, but if skipping the purge makes it easier for someone to manage on a regular basis, it should still be a major improvement over the most common methods homebrewers have been using for decades.

Disclaimer: I do the full water purge myself, and if I were going through the effort of following a full LoDO part process, I certainly wouldn’t cut any corners on this last little step.

 

[daveMN]

Has anyone had under attenuation problems fermenting in a corny this way? I'm 2 for 2 on underattenuated ferments. The first was a WY Bock yeast that stopped at 60%, the FFT was about 75%. This one, I didn't have my spund valve put together yet and I think the pressure got too high. The second one was Omega's Vermont Ale strain. The temp dropped on this one and the yeast dropped out. In both cases I couldn't get the ferment going by rousing. I'm starting at the bottom end of the temp range for the yeast and letting it free rise to target temp. I'm making a 2L yeast starter, 4L for the Bock. Aerating with oxygen for 2 minutes. Any similar experiences?

 

[schematix]

What pressure are you using?

 

[daveMN]

The Bock was all over the place, that one got up over 25 psi. The second one I used a blowoff tube for the first couple of days then connected to the keg and spund to about 5 psi. I used about 5 drops of Fermcap, but I don't think that was the problem. I'm going to pitch a 2L starter into an Alt tonight at about 55 degrees and let it rise to 60 and hold it there. Probably use a blow-off for the first couple of days then switch to spund at 5 psi. I'm thinking holding the temp and pressure consistently better than I have in the last two is key.

 

[schematix]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

 

[daveMN]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

I'll give 3.5 psi a try. I used a blow-off last time, but didn't get anything using the Fermcap.

 

[raysmithtx]

It’s possible. I don’t go over about 3.5 psi.

I also have switched to doing blow off for the first half of fermentation so I don’t get as much of a mess in my keg QDs and tubing.

Just curious how you are connecting your blow off to the corny keg.

 

[daveMN]

I put some 3/8" tubing over a mfl gas disconnect that goes to a jar of StarSan. I can take a picture of it tonight if you want.

 

[SanPancho]

Not certain but i think the number where you start to impede yeast growth and performance is around 10psi. 25 is definitely no bueno unless you are at FG or near it.

 

[schematix]

1/2” silicone tube zip tied over the gas post. Post and dip tube need to come out.

Too many small cavities in a keg disconnect for me. Pain to clean compared to this.

 

[crane]

Not certain but i think the number where you start to impede yeast growth and performance is around 10psi. 25 is definitely no bueno unless you are at FG or near it.

I regularly go over 10psi. Often times I will start between 5 and 10 psi in the first 12 hrs and hold it there for 3-4 days before raising it to 25psi for the remainder of the ferment.

 

[stonebrewer]

There are many posts out there by pro brewers who state they ferment at pressure in the ranges of 7-24 PSI and claim they have seen no issues with fermentation nor yeast health, as they repitch the yeast and it functions as normal. I personally start out at 10-15PSI and let it get up as high as 25PSI at the end to naturally carbonate. This also has an advantage of keeping the krausen compact, which makes the keg easier to clean. I have had no issues with fermentation, flocculation, or the like. I think the natural carbonation process is far superior to forced carbonation, as I don't get that "carbonic bite" in my naturally carbonated beers that I would get from forced carbonation. YMMV, but this has been my experience. Cheers!

 

[SanPancho]

I regularly go over 10psi. Often times I will start between 5 and 10 psi in the first 12 hrs and hold it there for 3-4 days before raising it to 25psi for the remainder of the ferment.

exactly. by day 4 or 5 the growth phase is long over and you're probably even finishing up with primary. if you've stayed under 10psi then you wouldnt see these problems.

finishing up over 10psi is totally different than starting it there.

 

[schematix]

Some perspective here too...

Every 30” of beer in a tank exerts 1 psi. (I know this isn’t exact, but close enough)

Applying 20 psi is like having a 50’ tank.

 

[stonebrewer]

Some perspective here too...

Every 30” of beer in a tank exerts 1 psi. (I know this isn’t exact, but close enough)

Applying 20 psi is like having a 50’ tank.

That is pressure from weight. Pro brewers also add pressure from natural CO2, so they can carbonate. Again, many pro brewers on other forums claim to ferment under a decent amount of pressure (20 PSI+), without issue. My personal experience has been similar. <shrug>

 

[schematix]

Pressure is pressure regardless of source. My point is that you are in effect simulating an enormous tank, larger than is normally used, by using that much pressure. The shape of primary tanks are much different than those used as secondary/brite tanks.

I experienced sluggishness as well at higher pressures... that's one reason why i went to blow off tube until closer to the end of primary. I don't think pressure is necessarily a good thing when strictly considering yeast.

I'm doing primary for ales in about 2-3 days and lagers in 7-8.

 

[daveMN]

Here's the setup I have right now. I connect to the SK outside the ferm chamber. With the Fermcap, I haven't had krausen come out of the gas post yet, but that could change with this batch. TBD.
I pitched WY1007 last night at 56F with 2 mins of O2, 5 drops of Fermcap, and a pinch of yeast nutrient out of an overabundance of caution. Then I purged the headspace and added the blow-off in the picture. I'll let the temp free rise to 60F. Should I attach the SK and spund when the ferment starts to slow, or wait a little longer?
Hopefully it's ready to ship for a comp on 1/26. Cheers!

 

[schematix]

With the Fermcap, I haven't had krausen come out of the gas post yet, but that could change with this batch. TBD.

Then you're not filling the FV full enough

Should I attach the SK and spund when the ferment starts to slow, or wait a little longer?
Hopefully it's ready to ship for a comp on 1/26. Cheers!

I usually wait until about 50% AA, or until i'm confident the kraussen isn't going to come through. At that point i'm not spunding for carbonation though. I'm spunding to seal the system and give me enough pressure to push samples out so i know exactly when to rack.