I have been on a long journey toward a completely closed cold side in my brewery. This is the last element. A while back, I made the switch to fermenting in a 10 gallon corny, with the intention of doing pressure fermentation with an adjustable PRV (aka spunding valve) I got from MoreBeer, but never quite got there. (Just improvised a airlock in the interim.) Now I'm finally implementing this, and said in another thread I'd report.
Let me start by thanking ynotbrusum for the simple question that lit the fire under me to finally implement this, and BrewBama for pointing me in the direction/ down the rabbit hole of the information I still needed to do so.
The PRV itself is a little janky, but I understand that it is intended to be a safety device and not a precision regulator, so that's acceptable. It will just take some ongoing fiddling to get it to hold somewhere in the ballpark. And it can't be set terribly low, as the rising stem will be so far out on the threads that it's unstable. But it is perfectly adequate for the job, as far as I can tell so far.
Yesterday I brewed, pitched dry S-04 at 72°F, pressurized the fermenter, set the PRV to 6 psig, and set the fermentation chamber temperature control to 60°F.
Overnight temperature dropped, and pressure dropped to just below 3 psig during the lag. This can't be accounted for just by cooling; obviously it was mainly gas going into solution, as in tests cooling an empty fermenter had minimal effect on pressure. And it occurs to me that the gas going into solution will include oxygen, as the fermenter was just pressurized, not purged. Seems an easy way to oxygenate wort.
At 24 hours from pitching, fermentation temperature is at the desired 64°F, and pressure had risen to 8 psig, so I'm fiddling with the PRV some more to try to get it to hold somewhere in the range of 5-6 psig. Think I'm figuring it out.
At 48 hours I'll take my first sample, which will be a greatly simplified procedure now, as I won't need to get a gas supply to the fermentation chamber. I'll report then how fermentation progress compares to past experience.
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