Frozen beer inside fermenter?

[NigeltheBold]

Here's a new one (for me at least):

I fermented a pale ale for about two weeks, dry hopped for 5 days, then cold-crashed the tank down and held it there for another week or so. I do that with all of my beers and they usually turn out great. But when I went to transfer the beer from fermenter to serving tank today, I noticed that for some reason, I only transferred about 75% of the beer (it stopped flowing, so I turned off the pump and closed the valves). Had no idea why I would only end up with 75% of what I normally end up with, so I looked in the top of the fermenter and WOAH! There is a 2-3" block of frozen beer/water around the inside wall of the tank. What happened? I had the temperature controller set to 36 degrees F, which is what I always set it to. But it's almost as if the beer in-contact with the tank walls was frozen by the glycol in the jacket. FYI, the glycol temperature in the chiller is set to 24 degrees F. I'm running a 33% glycol solution. This has never happened before, through more than 120 batches.

What can I do to prevent this in the future, and what should I do now? Let the frozen stuff thaw-out and add it to the beer in the serving tank? Or just dump the whole batch? Or just serve what's in the serving tank?

What a weird situation...

[TGTimm]

24 F is too cold for the glycol. Almost all glycol chiller units are optimized for about 27 F, and efficiency drops rapidly when trying to go below this--and you risk freeze-concentrating your beer.

To be perfectly legal, you need to add that lost 25% back with sterile water--you've just freeze-concentrated your beer, which falls under distillation as far as the law is concerned, and has raised your ABV by an equivalent amount.

I'm not even sure that adding the water back is legal after the product has been "enhanced".

[Jim Lieb]

I have had this happen before. Be careful when you chill your fermenter. If you cool it to fast ice forms. It only occasionally happens to me on two of my five fementers. I cool it to 40F in 10 degree increments, then no more than 2 degrees F, at a time after that.

[dberg]

Not knowing where your thermowell/jackets are located, I've seen tanks with a cone jacket and a high top jacket and the thermowell somewhere in between. Water becomes more dense when cooling to around 39F, then it starts becoming less dense (ice cubes float). If you have your top jackets on once the beer is below 39F, the top will freeze.

[BrewinLou]

Agree with Timm,
You are most likely running your chiller below its design. Contact your man and ask before you damage it.

[NigeltheBold]

I turned the glycol up to 26 for now. I'll talk to the manufacturer.

I think the problem happened because I attempted to have two tanks crashing at the same time. The tank that was further down the line never got cold enough, so glycol kept flowing and flowing. I bet the glycol was too cold and it was flowing too much, too fast. So next time I have to crash two tanks, I'll make sure I do it slowly.

I purged the fermenter with CO2 and let the ice melt, then transferred it into the serving tank with the concentrated beer. So technically, it should be back to the original alcohol level. I'll take some measurements and do some taste-testing to see if it turned out okay, but I don't have my hopes up.

Thanks for the advice.

[TGTimm]

A couple of points:

Don't worry about damaging your chiller unit by setting the SP too low--as long as the glycol is mixed for 10-15 F lower than the SP, you won't damage anything--just waste energy. We ran our Pro chiller for years at 22F, and it's still going strong. We froze the jackets frequently, and the compressors ran almost constantly, but it worked--if poorly.

Form having frozen and thawed many a keg, I wouldn't be surprised if your beer is just fine after you add the recovered water back.

[jebzter]

I turned the glycol up to 26 for now. I'll talk to the manufacturer.

I think the problem happened because I attempted to have two tanks crashing at the same time. The tank that was further down the line never got cold enough, so glycol kept flowing and flowing. I bet the glycol was too cold and it was flowing too much, too fast. So next time I have to crash two tanks, I'll make sure I do it slowly.

I purged the fermenter with CO2 and let the ice melt, then transferred it into the serving tank with the concentrated beer. So technically, it should be back to the original alcohol level. I'll take some measurements and do some taste-testing to see if it turned out okay, but I don't have my hopes up.

Thanks for the advice.

This brings up a question on how your glycol loop is configured, do the tanks run in series? And do you have a first out first in configuration? You will need to balance the flow rates to each tank, first with setting up the loop properly and second you can use globe valves or flow balancing valves at the glycol out of each tank. If you do that, your tanks should see even flows and you will be able to crash more than one at a time.