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Thread: Why does my kegged beer has huge amounts of yeast still in suspension

  1. #16
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    Quote Originally Posted by ipabrewer View Post
    Thank you, Mike. I need to think on what you are saying.

    In the meantime, a follow-up to Peter. We were discussing the ratio and temperatures. Here's what we are at for the moment:

    1) Temp Controller for the reservoir is set to 28F. We tried 20F but we were getting ice inside the unit and in the lines.
    2) Using about a 40% glycol ratio.
    3) BRIX reading on the mix is ~23 and SG is ~1.094
    4) We can not chill below 43F (at least, not with 2 fermenters running at 67/68F and the third trying to cold crash, even after sitting for 2 days).
    5) EDIT: By the way, our ambient temp is 67F or lower year round (we still ferment about 1/3 of our brews in plastic with no chilling; worry not; it's mostly saisons!).

    Is there anything about that we should change, and how so?
    If your ambient is that low, I don't know if better insulation will help all that much--I was thinking it was much higher ambient temp in there.

    Does your glycol temp stay near 28F when you're cooling two fermenters and crashing one? If the glycol reservoir temp goes up to 33-35 or higher, then that's your problem...the chiller is under-sized. I've been told recently by a refrigeration guy that as a rule of thumb, I shouldn't expect to get closer than 10F to the glycol temp across any heat exchange boundary. I think that's a bit conservative, but since your vessels aren't highly insulated, maybe closer to the reality for you.

    The way he explained it (he was talking about a specific refrigerant that was in the chiller): A Freon evaporator temperature of 18F means the glycol is at 28F and whatever you're cooling, a fermenter or walk-in, is a minimum 38F. Trying to do better than that will take a LONG time, because the heat transfer rate is proportional to the difference in temperature. The close the temp difference, the less heat flows. This doesn't include counter-flow heat exchangers, which are way more efficient because they maximize the "delta-T" between the hot and cold side.

    So, measure the temperature of the glycol where it enters the fermenter under load. That should tell you a lot.

    Regards,
    Mike

  2. #17
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    I think the 10F temp difference is a bit conservative as well, we run our glycol at 28, and have zero problems getting to 33 on fv, and 32 on BBT if the carbonation stone is on. This assumes that their chiller has the capacity to remove all of the heat going into the tank. It is far more likely that either the flow rates of glycol, or the tanks themselves are not adequate to effectively remove heat. For the glycol to be effective, you will need sufficient flow, and contact time with the beer, also cooling should take place not only on the cone, but also the upper third or so of the tank to promote convection.

    Quote Originally Posted by rdcpro View Post
    If your ambient is that low, I don't know if better insulation will help all that much--I was thinking it was much higher ambient temp in there.

    Does your glycol temp stay near 28F when you're cooling two fermenters and crashing one? If the glycol reservoir temp goes up to 33-35 or higher, then that's your problem...the chiller is under-sized. I've been told recently by a refrigeration guy that as a rule of thumb, I shouldn't expect to get closer than 10F to the glycol temp across any heat exchange boundary. I think that's a bit conservative, but since your vessels aren't highly insulated, maybe closer to the reality for you.

    The way he explained it (he was talking about a specific refrigerant that was in the chiller): A Freon evaporator temperature of 18F means the glycol is at 28F and whatever you're cooling, a fermenter or walk-in, is a minimum 38F. Trying to do better than that will take a LONG time, because the heat transfer rate is proportional to the difference in temperature. The close the temp difference, the less heat flows. This doesn't include counter-flow heat exchangers, which are way more efficient because they maximize the "delta-T" between the hot and cold side.

    So, measure the temperature of the glycol where it enters the fermenter under load. That should tell you a lot.

    Regards,
    Mike

  3. #18
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    Quote Originally Posted by jebzter View Post
    also cooling should take place not only on the cone, but also the upper third or so of the tank to promote convection.
    In these fermenters, the cooling coil is in the top area. It in no way extends to the cone area. I believe the bottom of the coil is a few inches above the start of the cone and the top of the coil is around the 28gallon mark, leaving about 3 gallons of beer above the coil, though I'm not sure how accurate my assessment here is: It might be that the top of the coil "sticks out" above the beer in the headspace. Who that distinction make a difference?

    The glycol chiller is older, so it might be the culprit. I have not tried the SS Brewtech conicals using their own glycol systems (yet).

    What did y'all think about the numbers I posted (BRIX of the glycol mixture and temperature settings)? Should I attempt to add more glycol and lower the reservoir's temperature setting, and if so, any guess as to suggested amount and temp?
    Wages Brewing Company
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  4. #19
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    Was there anything about these "settings" that I should look at changing? That is, this is what we are running currently. Should we increase our glycol ratio? Might that allow us to set the reservoir lower and therefore reach a lower cold crash temp?

    1) Temp Controller for the reservoir is set to 28F. We tried 20F but we were getting ice inside the unit and in the lines.
    2) Using about a 40% glycol ratio.
    3) BRIX reading on the mix is ~23 and SG is ~1.094
    4) We can not chill below 43F (at least, not with 2 fermenters running at 67/68F and the third trying to cold crash, even after sitting for 2 days).
    5) EDIT: By the way, our ambient temp is 67F or lower year round (we still ferment about 1/3 of our brews in plastic with no chilling; worry not; it's mostly saisons!).
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  5. #20
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    According to GD Chillers, 35% glycol to water (24.75 brix) is ideal. The more glycol in the water, the poorer the heat transfer. Depending on the HX in your chiller, you may be able to see if there's ice forming (in mine the evaporator is a simple finned coil directly immersed in the tank, from a soda carbonating machine), so the less glycol you use, without forming ice, the better. If you know your evaporator temperature you can figure out the exact ratio you need.

    Regards,
    Mike

  6. #21
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    So we are just shy of that. Ergo, we should add a little more glycol and see how it goes.

    Agreed?

    As an aside, I'm looking to buy a brite tank and another glycol unit. I need something jacketed in the 2 to 3.5 BBL range but that can still carb as little as 1 BBL of beer (ergo, the placement of the carb stone makes a big difference). Any recommendations for the bite tank and/or glycol unit to go with it?
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  7. #22
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    Your tanks have an immersion coil for cooling? There's your problem, it is cooling against what would be the natural convection in a cylendroconical tank. Immersion coils are not ideal for larger FV. Poorer heat transfer, its a much much smaller surface area than what is usually on a jacketed tank. Out of curiosity, are your tanks properly insulated on the outside, we have nearly 3 inches of expanding foam between the cladding and the tank.

  8. #23
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    If this has been the first time there's been a problem with this recipe, and no other factors have changed, I would be looking at the yeast first. It's possible it was just a bad batch. It's also possible there is also a slight contamination in the tank taking hold before the yeast went to work. While what everyone is saying and suggesting about temperature and the glycol system is correct, if this hasn't been a problem for you before, and you didn't change anything about the process, I would look at ingredients first. I'm able to chill down to 32F and every once in awhile I'll get a batch that won't clear at all. If you can culture or scope the yeast you'll know pretty soon if that was the issue. You may want to see if the calcium content of your water has dropped. Also adding .5-1g of zinc 15 min EOB will give your yeast the nutrients they need and aid in floccing.

    Is every keg cloudy or just the two you put on? At what point in the kegging process were those kegs filled? Do you hook up a sight glass when you keg?

  9. #24
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    Quote Originally Posted by jebzter View Post
    Your tanks have an immersion coil for cooling? There's your problem, it is cooling against what would be the natural convection in a cylendroconical tank. Immersion coils are not ideal for larger FV. Poorer heat transfer, its a much much smaller surface area than what is usually on a jacketed tank. Out of curiosity, are your tanks properly insulated on the outside, we have nearly 3 inches of expanding foam between the cladding and the tank.
    That's interesting regarding the convection. Sounds sciencey. The only insulation is the neoprene jacket provided with the unit by SS Brew Tech. Someone earlier proposed that we further insulate the tanks.

    But then there is the next fellow's comments....
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  10. #25
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    Quote Originally Posted by adw1984 View Post
    If this has been the first time there's been a problem with this recipe, and no other factors have changed, I would be looking at the yeast first. It's possible it was just a bad batch. It's also possible there is also a slight contamination in the tank taking hold before the yeast went to work. While what everyone is saying and suggesting about temperature and the glycol system is correct, if this hasn't been a problem for you before, and you didn't change anything about the process, I would look at ingredients first. I'm able to chill down to 32F and every once in awhile I'll get a batch that won't clear at all. If you can culture or scope the yeast you'll know pretty soon if that was the issue. You may want to see if the calcium content of your water has dropped. Also adding .5-1g of zinc 15 min EOB will give your yeast the nutrients they need and aid in floccing.

    Is every keg cloudy or just the two you put on? At what point in the kegging process were those kegs filled? Do you hook up a sight glass when you keg?
    Thanks! Yes, I thought the same: We have done this identically (as best as I can surmise) for 20 batches of the same recipe and this is the first time this has happened. It DOES seem like a bad batch with the yeast refusing to flocculate out. On that, we are going to try using gelatin in those two kegs then transfer later on and (a) see if that clears the beer (I'm sure it will) and (b) see if the beer tastes good after that. TBD. This will also be our first time removing a spear from a keg!

    To answer your questions: the cloudy beer is two 1/2 BBL sankes from a 1 BBL batch, so the entire batch. The beer was kegged in the same manner as many dozens of kegs in the past. We do not have a sight glass during kegging. We go from the the 43F crashed 1 BBL FV through the Thompson pump into the sanke kegs. We always get a fair amount of yeast in the kegs (presumably because we can't crash the FV below 43F, so there is still yeast on the sidewall of the conical), but it always drops out and after a few pours, it's gone. In this case, I poured over a gallon out of each of the kegs after being stored at 33F for a week, and it still would not run clear. **I'm getting closer and closer to budgeting for some lab equipment so we can assess our yeast better.

    Incidentally (follow-up up on the previous discussion about the glycol), we added enough glycol to the reservoir to reach ~25 BRIX, then we lowered the reservoir temp from 28F to 26F. That occurred yesterday. Today we are going to see if we can chill below 43F without the reservoir freezing up.
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  11. #26
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    FOLLOW-UP: We reached 41F yesterday with the improved glycol mix! We will be trying to go lower with our next crash. I doubt this is the answer for our "yeast still in suspension" beer, but it does mean improvements for normal brews.
    Wages Brewing Company
    West Plains, Missouri
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  12. #27
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    Quote Originally Posted by ipabrewer View Post
    That's interesting regarding the convection. Sounds sciencey. The only insulation is the neoprene jacket provided with the unit by SS Brew Tech. Someone earlier proposed that we further insulate the tanks.

    But then there is the next fellow's comments....
    Physics is pretty important to brewing. I would second increasing the insulation, 1 inch or 1.5 inch of neoprene is way less than larger commercial vessels. I would also recommend getting a sight glass, it will help you a bunch. The best way to get as much yeast out is get cold, can't stress this enough, 35 or below, or the finings you are using will be way less effective.

  13. #28
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    I always sucked at physics. Honestly wouldn't have passed except the teacher graded on a curve and it was rare anyone scored over 80 out of 100. or rather But I am prepared to do what I have to do to improve our situation.

    UPDATE: We now have the glycol reservoir at 24F (down from 28F) without any ice build up. So tomorrow we will attempt to crash cool to 38F on 1 fermenter while the other two are at 68F. Did I mention we already got one down from 43F to 41F after we added more glycol? Happy making.
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  14. #29
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    UPDATE: The moment the chiller started cooling below 40F, the solenoids started freezing up, so we've still been unable to chill below 40F (but we did get from 43F to 40F, so that's some improvement).

    So the next goal is to insulate the glycol lines and see what kind of improvement we get from that.

    ***Sure would be nice if there was a manual to using glycol systems!
    Wages Brewing Company
    West Plains, Missouri
    The Middle of Nowhere Never Tasted So Good!

  15. #30
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    Check the rate of flow on your glycol loop

    You might want to check the rate of flow on your glycol loop. If you are moving too slow or too fast, this can cause issues. Most tanks should have around 10 GPM flow through jackets. Check your bypass valve at the end of your loop.

    Also your tanks should be plumbed first in, last out in order to not heat up the glycol to tanks down the line.

    In my experience, 23 Brix and 28*F should be perfectly fine.

    Can't say about the beer if your system was fine for many brews before this, it's unlikely related to the temp. But you should absolutely be able to get your beer down to 35*F minimum. That will help significantly either way.

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