Freezer fermentation control

Discussion in 'General Brewing Discussions' started by Bubbles, Jun 12, 2021.

  1. Bubbles

    Bubbles New Member

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    OK, I know this is probably an issue many of you have addressed a billion times, but I couldn't find what I needed from the forum archives. I'm seriously close to buying a chest freezer (7 cubic feet) and have a controller to keep fermentation temps down. I've read that the temp inside the fermenter (I"ll be using plastic "big mouth" carboys) is something on the order of 5 - 8 degrees warmer than the ambient temp inside the freezer. I plan to use a temp sensor taped to the outside of the carboy and insulated by styrofoam. I believe that should give me a fairly accurate temp of the contents. So here's where I get confused: if the temp of the fermenting wort is exothermic, can you expect the ambient freezer temp to keep the fermentation temp within a reasonable temp range? Or do you start with the wort temp at the lowest temp on the suggested range of fermentation temps for that specific yeast and assume it will rise up to the middle or high end of that range? I guess these questions come down to the overarching question about how much effect the ambient temp of a freezer has on controlling the temp (cooling) of fermentation. I plan to brew an ESB to start where I'd expect fermentation temps could be 64 - 72 or so.
     
  2. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I use a similar setup. I tape a temp probe to the fermenter. The beer will warm as it ferments from the exothermic activity of the yeast. The beer will keep the temperature uniform throughout the fermenter during the most active fermentation because the beer itself will churn, it’s a built in mixer. I don’t believe that a thermal well is really necessary, you will get within a degree or so with the probe tape to the side. The insulation over the probe increases accuracy.

    Adding a fan to circulate the air inside the fermenter helps a lot and I would highly recommend it.
     
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  3. Nosybear

    Nosybear Well-Known Member

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    I've tested the "warmer in the middle" hypothesis and it did not survive. My stainless fermenter has a thermowell. During active fermentation, I can check temperature at the surface (stick the probe in until the stainless part is gone) and in the middle (stick the probe in all the way). The readings are within a couple tenths of a degree Celsius of each other. Our vessels are too small for the temperature difference to form, the natural convective movement seems to evenly distributed the heat. Tape the probe to the outside, works fine.
     
  4. Bubbles

    Bubbles New Member

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    That sounds like a reasonable solution to preventing some sort of layering of various air temps within the freezer. Would placing the carboy (I don't have a valve at the bottom of the carboy, just siphon off the beer) in a small container of water help to even out the temp swings, or do you think the circulating air temp will regulate the fermentation temps adequately -- ie, do you find that your fermentation temps are kept within the recommended range for the yeasts you use? Do you direct the fan toward the fermenter to cool it? I'm mostly concerned about the temp swings upward that may not be controlled by ambient temps, even with a fan blowing on the fermenter.
     
  5. Bubbles

    Bubbles New Member

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    OK, I can believe that, at least in the initial, more active, part of fermentation, that there aren't large differences in temp within the fermenter due to the churning that is observable. But the concern I have is how far the temp may rise by relying on ambient temps within the freezer, that is, the ability of ambient relatively cooler temps to essentially transfer the exothermic heat produced by fermentation into the freezer chamber and then be cooled by the function of the freezer. I have concerns about how well the freezer may work in reducing the fermentation temps but I think HVMan may have a good idea by placing a small fan within the freezer chamber. Basically, my lack of understanding of the viability of transferring heat from fermentation into the freezer is what holds me up from pulling the trigger and buying the freezer. That is, how effective is fermenting in a temperature-controlled freezer in keeping the swings in temp from being too large? From what I've read, it's the changing temp environment that affects yeast performance, not just the higher temps themselves.
     
  6. Minbari

    Minbari Well-Known Member

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    During fermentation yes. After? I can measure a 5 degree difference from surface to the bottom once the churning stops. Not much you can do about it
     
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  7. 4Bentley

    4Bentley Active Member

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    During fermentation there is a lot of churning in the fermenter so the difference in temperature is minimal. I set the controller to a 1 degree tolerance so when the temp gets 1 degree above setting the refrigerator comes on and cools it down within a few minutes. Everything is pretty stable as long as the yeast is active.
     
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  8. Craigerrr

    Craigerrr Well-Known Member

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    ...and, once fermentation is complete, the temperature differences don't matter
     
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  9. Craigerrr

    Craigerrr Well-Known Member

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    Consider a cheap used fridge, and an inkbird controller. Lifting the carboy in and out of the chest freezer will be hard on the back, and dangerous. Then the fridge has a built in fan, and humidity control. Either way taping the sensor to the outside will be totally fine. Yeast temperature ranges are pretty wide (US-05 is 15C to 24C for instance), so picking a conteol temperature in the middle of the range, and fluctuating plus or minus a degree is not going to be an issue at all. It will in fact be ideal!
     
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  10. Trialben

    Trialben Well-Known Member

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    Your temp controller that you have the freezer pluged into will negate your concern of "raising ambient temperature".
    with an STC 1000 You can set the ferment difference .3c meaning the fridge/freezer will start cooling once the fermentor reaches .3 above set point.

    Realistically temp control is ideal for the primary fermentation phase once secondary phase begins it's more or less maintaining then ferment temp and or even raising the ferment temp.
     
  11. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I don’t put the sensor in a container with water, I tape it to the fermenter or place it in the air stream coming off the fan. First, not all probes can take it, they aren’t always sealed well enough to submerge in water. Second, the fan works very well both for keeping the carboy cool or heated by moving air across the surface of the carboy. Plus if you cold crash or condition the beer, it maintains even temperatures throughout the keezer.
     
  12. Blackmuse

    Blackmuse Well-Known Member

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    Put the probe against the fermenter, put a piece of foam over it and tape it down. Works great. No fan needed. The probe reads the fermenter and the freezer kicks on according to your set point boundaries. I use 1 degree F and have very good results. My old upright freezer does a great job of keeping things consistent. IMO - You might be thinking too hard on this one. Pull the trigger.
     
  13. Hawkbox

    Hawkbox Well-Known Member

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    This is what I do, I have a Keezer for kegs but my ferm chamber is an old mini fridge. Don't stress about temp differentials in the chamber, the movement of the beer will address that on it's own.
     
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  14. BarbarianBrewer

    BarbarianBrewer Well-Known Member

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    I completely agree with all the advice given so far. I also have a 7 cu ft chest freezer. Lifting 5-6 gallon carboys out of it wasn't too difficult (most of the time). But, when I went to a 30L (8 gal) Speidel, I decided I needed the assistance of a block & tackle setup. You'll need to decide for yourself how your back will handle the lifting. Regarding interior fermenter temperature vs ambient temperature: A few years ago I borrowed a coworkers Tilt hydrometer for a couple batches. Even during active fermentation the Tilt only read about 3 F above the Inkbird temp probe taped to the side of the fermenter. (The probe was covered by a piece of styrofoam). Since then I usually set my Inkbird controller in the lower third of the yeast's optimum temperature range so that the temperature of the wort will be in the middle third of that range. Or if I want to ferment near the top of the yeast's range I set the controller near the middle of the yeast's range.
     
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  15. Trialben

    Trialben Well-Known Member

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    Remember there are pumps and co2 great for pushing wort n beer around.
     
  16. Frankenbrewer

    Frankenbrewer Well-Known Member

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    The last few batches I have had two ferms going at the same time. The problem is trying to regulate the temps for both batches. Currently, the two in the chamber now are 2 degrees different. I do not have the temp probe attached to either fermenter. I just have it hanging about 12 inches off the bottom between the fermenters. None of it is exact but it is working for now. Anyone do anything different when there is more than one batch in the ferm chamber?
     
  17. Hawkbox

    Hawkbox Well-Known Member

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    Mine won't fit more than one so nope.
     
  18. HighVoltageMan!

    HighVoltageMan! Well-Known Member

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    I am fermenting 2 lagers right now in one chamber at 48F. One has the controller probe attached to the outside of the fermenter, the other has just a thermometer attached. Both are either right on or off by a degree at the most. The key is to put a fan in the chamber. I know a lot of people say it isn't needed, but it keeps the air moving and the temperature consistent throughout the chamber.
     
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  19. Frankenbrewer

    Frankenbrewer Well-Known Member

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    I'll try that the next time or just brew one batch at a time......weekly!:D
     
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  20. Craigerrr

    Craigerrr Well-Known Member

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    Back when I brewed 10 gallon batches (just a year ago), I fermented in two fermenters in the same chamber (a fridge with inkbird).
    I had the probe in one fermenter, and just trusted that the other fermenter would follow along, I never noticed any difference in the finished beer from one fermenter to the other.
     
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