Question about Temperature in my Chest Freezer

I use a chest freezer and a temperature controller to keep the fermenting temperature at 20 degree celsius. The thermometer (A) connects with the temperature controller is dipped into a small jar of water in the chest freezer. Another thermometer (B) is to test the air temperature inside the freezer.
Well, I notice that when thermometer (A) is at 20 degree celsius, the thermometer (B) is at around 23-24 degree celsius, so I suppose it is a bit higher. Then I set the controller to keep the thermometer (A) at around 15 degree, now the thermometer (B) shows 20 degree. I have using this thermometer to ferment. Is this correct? Maybe it is a bit too low? As several batches of my beer taste diacetyl, aldehyde and polyphenol...

Any advices will be much appreciated.

 

Better would be to attach the probe to the side of the fermenter. I use an "Ace" bandage that I wrap around the carboy. I place the temp probe under it, and also add a bit of cardboard to help insulate a little bit against the air. It's nice and simple, though it'll read a few degrees lower than the actual temp in the center of the liquid, where fermentation warms things up.

 

Unless your water is also fermenting you aren't really controlling the fermentation temperature. Do as the previous poster said and attach the probe to the fermenter as the yeast activity will raise the temperature of that above the temperature of the water which then raises the air temperature in the freezer.

When you attach the controller to the fermenter, attach your second thermometer to the fermenter also because the air temperature in the freezer doesn't matter and may be well below the temperature of the beer.

 

Better yet figure out a way to get the temp probe inside the beer. What type of fermenter and temp controller are you using?

 

I am using simple equipments like 5 gallons pure water barrel and a cheap temp controller with air and water tentacle...

 

The container of water will stay cold longer after the compressor stops than the air around it will. If safe to do so, put thermometer B in the water with the thermostat sensor to see if they then agree.

 

Yeast is exothermic, meaning it produces heat. The temperature of fermenting wort/beer can be 5-10 degrees Fahrenheit/2.75-5.5 degrees Celsius, higher than the ambient temperature.

So you want to take the temp of the fermenting beer/wort, not the surrounding environment. As noted above, you can attach the temp probe to the side of the fermenter and insulate it so it draws the temp reading from the fermenter and not from the ambient temp in the freezer. Here's a pic showing how i do it, there are 20 ways you can do this. I have some closed-cell foam I use, others have used styrofoam, towels, cardboard, whatever you've got to get a thick enough insulation over the probe. Then an Ace-bandage, bungee cord, even string could hold it there.

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Using your current setup, the *air* in your freezer will fluctuate quite a bit in temp as the freezer works to lower the temp of the water in your jar. It's not going to do as much to the fermenter as it's a large thermal mass, so the air temp isn't as critical as the temp in your jar of water.

But place that temp probe against the fermenter and insulate it. You'll be glad you did.

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Pic one shows the temp probe being held against two fermenters; I like the gender equality of using both pink and blue foam.

Pic two shows another fermenter with a heat mat inside the straps; the probe is on the back side so you can't see it, but you can see that same heat mat in pic 1, plus on the left fermenter you can see a reptile heat mat.

Why heat mats? Because I typically ferment ales at 64-67 degrees F, and toward the end I like to ramp up the temp to 71 or so for the yeast to finish up. Also, I live in Wisconsin/USA, where in the winter my garage temps can get down near freezing. I need a heat mat inside the fermentation chambers to keep the fermenting wort warm enough.

 

I use a stopper with the temperature probe in a thermowell. I think that provides the best reading because it is directly inside the liquid.

 

I agree with controlling the temperature of the fermentation. Having the a vessel of water does not accomplish this. The probe in the air will almost always be different than the one in water or the wort. Air temperature will swing high when the wort is too cool and low when the wort is too warm. The tape to the side method is good. I got and prefer a thermowell. I also heard that many sensors will eventually leak from the cable/sensor joint and fail. I keep mine out of liquid.

Another thing to check, is do the two thermometers read the same just sitting on the same surface. I had an instance where I wasn't sure my thermometer was reading correctly so I measured with 4 different thermometers - guess what - 4 different temperatures - the glass lab thermometer was reading 60 degrees and the digital ones 150- 155 degrees for the mash. I used the one that was in the middle. Then calibrated that one in ice water and boiling. It seems accurate.

 

Sounds interesting. Could you please provide a picture of it?

 

https://www.morebeer.com/products/s...MItsG_jJfH3AIVi5-fCh1DKw6QEAQYAyABEgJeQvD_BwE

 

I use the one from www.ballandkeg.com, but I bought it to be able to pump ice water through my fermenter.

 

Much much cheaper here. I just bought three.
https://www.amazon.com/dp/B0763SFLLX/?tag=skimlinks_replacement-20

 

That is cheaper for sure if you only need the thermowell. My stopper from www.ballandkeg.com includes a blow off tube and the stainless steel cooling coil. I use that to cool my wort during fermentation. I think that justifies the price difference, but your unit is fine if you only want a thermowell and have some other way to cool your fermentation.

 

This looks interesting.

How consistent is the wort temp throughout the fermentor? Also what is the lowest temp you have achieved?

Thanks!

 

Sorry it took so long, I haven't been on in a while. I can easily control temperature in my 6 gallon fermenter at lager temps, low 50's F in a room that is mid-70's in the summer. I go through two or three 2-liter ice jugs in 24 hours to do that if I keep the fermenter insluated with a blanket or two. My ice jugs are in a styrofoam cooler with a small pump and I use an Inkbrid with the probe in the thermowell to control the pump. The temperature seems to be very consistent throughout the fermenter, especially during active fermentation.

I have tried to cold crash with the system and was only able to achieve mid-40's. I think I would need glycol cooler than 32 F to get down below that.

 

Thanks for replying.

This looks like a great alternative for folks that don't have room for or do not want to invest in a ferm fridge or chamber. I think it could also be adapted to cool 2 or more fermenters at the same time and at different temps using a larger ice chest and multiple pumps.

Very cool