Mystery cooling on our double-batch fermentors

[jscottAT4]

Updated: was isolated to one tank, found faulty solenoid valve.

Hi All,

Just an update.

We have made some pretty significant changes to our brewing process. Some of these changes:

-Same day double batching into 14/15BBL, 2 day quad-batching into 30BBL
-Aeration of first half of wort volume ie batch #1 in double batch, #1 & 2 in quad batch. (O2 only stays in solution for 3-6hrs. Here at elevation in CO, its about 4 hrs for us)
-Pitching after #1 of double batch, or between 1 and 2 of quad batch.
-Warmer knockout (75) and warmer FV temp until fermentation starts (any sign of airlock activity)
-MUCH better yeast harvesting/handling/storage/counting/pitching

Through these changes and many more, we pretty much resolved this mystery cooling issue.

However, a few months ago we noticed one of our 14BBL tanks dropping its fermentation temp. It had very active fermentation, as indicated by the airlock. We verified the set temps and temp probe. We were able to isolate to a faulty solenoid valve that controls glycol input to the tank. Noted a slight rumbling on the tank's glycol lines and they were slightly cooler than other static tank lines, so we suspected there was some slight glycol flow through a closed solenoid valve. We replaced the solenoid diaphragm, and the issue seemed to be immediately resolved.

If I had to wager a guess, I would bet our issues before were due to temperature stratification, poor yeast health. The warmer knockout temps, better yeast management, and same-day double batching have yielded some very healthy fermentation, with no further temp issues.


Cheers!

[jscottAT4]

We have since done our double batch and had no issues with extreme unexplained temperature drops.

However we did a few things different:
-Did not pitch until 2nd batch on day 2
-Knockout was about 4 less than ferm temp.
-Setpoint was set 2 above ferm temp so as to not activate cooling.
-O2 applied to 1/2 cast-out volume for both turns

My guess would be the knockout temp into the tank causes the issue. Based on the majority of your input, i think there is temp stratification. Going intentionally a few degrees lower than setpoint vs at or above to ensure to glycol flow. We're also going to try flowing through downtube 90deg to right with 2nd turn to help mix total volume.

Thanks all for your input!

Hello,

Just wanted to pass along some info we learned "the hard way" regarding aeration and DO in your wort. We had a few drain batches due to poor yeast health, which fed other batches and caused subsequent problems.

Check out Wyeast's info on Aeratyion here:

http://www.wyeastlab.com/oxygenation

From the page:

Some yeast strains have higher oxygen requirements than others. It is generally safe to assume that you need at least 10ppm of oxygen. 10ppm will supply adequate oxygen in most situations. Over-oxygenation is generally not a concern as the yeast will use all available oxygen within 3 to 9 hours of pitching and oxygen will come out of solution during that time as well. Under-oxygenation is a much bigger concern.

We Aerate the first 1/2 of the volume, and pitch the first day so the yeas has access to all of that O2. Pitching the next day led to sluggish fermentation. A lot of our issues were due to aeration. If I pull a brink out in the AM, brew batch #1, and then pitch, I usually have airlock activity before I start flowing Batch #2 knockout. We have much healthier fermenation now, in about 3-4 days instead of 7-10 days. The yeast we the harvest is incredibly viable for re-pitching.