Chest Freezer/Temperature Control

Systems, Gear, & DIY
1

Greetings.  In an attempt to not make the same mistakes on my second batch that I made on my first (temperature control foremost, but not the only one) I have just purchased a 6.9cf chest freezer and an InkBird ITC-308 temperature controller to set up as a fermentation chamber.  The first batch, while I never saw the stick-on fermometer go above 72F during active fermentation, I can not guarantee that it didn’t, and it did get above 80F afterwards.  I’m trying not to make that mistake again.  So, on to the questions.

1: I will only be doing Ales (IPA, Hefeweizen, Porter, Stout, and maybe a Saison, Barleywine or Mead on a rare occasion).  I know that I will need to tape the probe of the controller to the carboy under a piece of styrofoam or other insulation for accurate temps.  If I wanted to ferment an IPA at say 65F, would I set the controller for 65F, or should it be set 2 or 3 degrees lower?

2:  Should the controller be set to turn the compressor on when the temperature is 1 degree higher than the set temp, or should I use a higher temperature differential?

3:  I have the freezer set up, but empty.  The controller is set at 63F and the controller shuts the compressor off at the set temp.  The freezer, however continues to chill to below 60F even after it is shut off.  I know that the ambient air temp is not what I will be going by during fermentation, but will that temperature difference cause a problem, or will the wort hold temperature good enough that this will not be a problem?

4:  In reference to #3, would it be wise to just go ahead and put a reptile heating bulb in the freezer just to be on the safe side or would it just be a waste of money if the difference between the set temp and the air temp will not be an issue?  The freezer will be in a room in the house that stays between 75F and 80F year round.

5:  Should I set the thermostat on the freezer to the coldest setting, the warmest setting or in the middle.  I have never set up a freezer on a controller like this, and not sure what the best way to do it is.

6:  My 6.5 gallon carboy is 25.5" tall with the airlock installed.  The freezer is 26"  from the floor to the lid.  is .5" enough clearance between the airlock and the lid enough, or should I just go ahead and get some 1" tubing and set up a blow-off hose?

Thanks for taking the time to read through this and offer your guidance.

Erik

2

Those are great questions. Selfishly, I have replied here so when the guys who know will answer and I can quickly find the post to apply it to my set up.

3

If by me asking questions, someone else gets the answers they need, the world is a better place.

4

  1. A properly insulated probe attached to the carboy will read within 0.5F of beer temp; use that as your baseline, do it the same way every time, and adjust from there. 65 via your process  will not be the same as 65 via someone else’s (don’t worry, you’ll still make great beer)

  2. 1 degree F delta is fine, even 2 is probably OK. I set mine to 1 when I’m fermenting and 2 when conditioning (to minimize compressor cycles)

  3. I don’t know the InkBird, but most controllers have a setting for this; if yours doesn’t, I’d set it a little above so it doesn’t overcool too far; don’t want to shock your yeast

  4. Probably won’t hurt, but in most cases probably unnecessary, especially in a 76F room

  5. Coldest, but it won’t really matter since your controller will turn it off before the freezer thermo will do anything (which is good)

  6. Should be. You can always cram the airlock a little further down if you need a little space; Worst case blowoff might help depending on how much room it takes for the tubing to make a 180 without getting pinched; I just crammed the airlock down a little farther

5

The controller does have a calibration setting on it.  Right now I have a glass of water with a thermometer in it sitting in the freezer and will adjust the settings over the next few hours, or day to get things evened out before I attempt to ferment in it.

Edit:  After thinking about it, I figured to be able to really get this thing set up, a thermometer in a glass of water was not sufficient.  I now have 5 gal. of water in a carboy with the sensor taped to the side and covered with a piece of Styrofoam.  I think this will give a better representation of how the freezer and beer will work together temperature wise.  Is using a carboy of water a good way to get things calibrated to keep a steady temp?

Edit #2:  Let my test setup go over night and everything looks good.  The temp was set at 65F, and the probe read 65.8F and the compressor was running.  The stick on fermometer, and a regular thermometer placed in the water both read 66F when I checked them this morning.  It doesn’t look like I will need to fiddle with the calibration at all with the results of this test run.

6

Overshoot will be quite minimal if you are sticking the probe to the outside of the fermenter. I would add a stick on LC thermometer to the fermenter as well.

7

I do have stick-on thermometers on my carboys, and it is reading pretty much the same as the controller.  I was worried about the air temp being so much colder than the set temp, but I can see now that it is not a problem.  As long as I stay within 1 or 2 degrees of the set temp, I am not going to worry.

I wanted my first batch to turn out better than it did, but I’m not going to let that discourage me.  I learned a lot from it to apply to the next one, and it makes me want to learn even more.

8

5.  Warmest, assuming that the freezer temp setting is cooler than the desired ferment temp.  Having it on warmest reduces the temperature overshoot (3 F in your experience) because the freezer is much colder than the desired fermenter temp.

9

Really? My understanding is that the compressor is either on or off and that the freezer’s built-in thermostat simply changes the set-point. Since even the warmest setting would ostensibly be “below” 32F this shouldn’t matter. That said, since we’re already using the temp controller to cycle the power on and off it seems that setting the freezer to “coldest” would be the safest, since it minimizes the chance for the freezer thermostat ever doing anything. Am I missing something?

10

If the thermostat cuts a freezer off at say at 32 F, then the freezer is still cooling the fermenter.  Stable temps are better than fluctuating fermentation temps.

11

Think you’re partially wrong here. The dial on the freezer is a thermostat, basically a switch that cuts off at a given temp. It is functioning the same as the external controller, but at a lower range. That said, warm on the chest freezer might be warmer than 32 which is where I crash. I set both my keezer and ferm feeezer to the cold side of the dial.

12

For 5, either setting should work just fine for fermentation.  To the OP: good investment.  Fermentation temp control really helped me make better beer.

13

The OP said the following: “3:  I have the freezer set up, but empty.  The controller is set at 63F and the controller shuts the compressor off at the set temp.  The freezer, however continues to chill to below 60F even after it is shut off.”

To reduce the overshoot of the cooling, the freezer thermostat should be set to a warmer temperature that is still below the desired temperature, say 10 *F below.  If the freezer thermostat cuts off the freezer at 10 *F below the ferment temp, it will still be cooling the fermenter.  Eventually, as the freezer warms up it will turn back on unless the ferment temp has hit its target in the meantime.

14

This still doesn’t make sense to me. The freezer has one compressor which has a binary control (power on or power off). Without a temp controller attached, the knob on the freezer controls the set point at which to power on or off. Let’s say the knob would control the ambient freezer temp between 10F (if set to max cooling) and 30F (if set to min cooling).

Now attach an external temp controller that is cycling the power from the outlet and set that controller to 63F. When the beer temp gets to 63 plus the delta temp (let’s say 1F), the controller will cycle the compressor on for MaxCoolTime minutes (Let’s say 15) and then leave it off for a minimum rest cycle (let’s say 10 minutes).

Assuming a set point in the 50’s or 60’s, you want the thermostat built into the freezer doing nothing. If you set the freezer knob to 30F (min cool), the freezer might prematurely stop cooling even though your temp controller is trying to cool. Now you’ve just got two different controllers fighting each other.

Maybe my understanding of this is flawed because I use a Fermostat and a BrewPi (both of which can “learn” your freezer’s propensity to overshoot and adjust). However, even if I were trying to handle the overshoot manually I’d rather deal with one thermostat than two.

Can someone tell me if this logic is correct or if I’m fundamentally misunderstanding something?

15

^^^ what he said unless freezers actually have some form of variable cooling capacity beyond on and off. As far as I know, freezers don’t function like a car cabin temp dial where it is a mix of a/c cooled air and heater rad.

Edit to add - I bet some fridges operate this way. Some top freezer model fridges utilize a simple damper to control how much cold air drops into the fridge box while some use fans. The versions with a simple damper would dump more cold air faster if set to be coldest setting which could create additional overshoot. This type of cooling should not be found on a chest freezer as far as I know.

16

That’s what I am hoping for.  I know my temperature control was the biggest of my blunders on that first batch.  All of the other things were procedural things that are easily corrected.  I had hoped for a much better first batch, but I can use it as a learning tool to make future beers a lot better.

As far as the freezer goes now, I have been monitoring it with 5g of water in a carboy with the sensor taped to the outside under foam.  I have it set to 65F with a 1F delta.  The compressor comes on when the water gets to 66F, and shuts off at a sensed temp of 65F.  I have yet to see it go over the 66F mark and the coldest I have seen on any of my checks has been 64.5F  I have no idea what the ambient air temp in the freezer is at this point, as I am only looking at the temp of the liquid.

For a test last night, I set the freezer control to its warmest setting, and this morning the test water was still at a steady 65F-66F, with the lowest temp being 64.5F.  This freezer has settings 1-7 on it’s thermostat, and according to the manufacture, a setting of 4 should maintain a temp of 0F.

Just from my observations, it doesn’t seem to matter where the freezer itself is set to maintain a temp of ~65F in the liquid for fermentation.  I have not done a simulated cold crash with the freezer set at different settings, but I would guess for that, I would have to have it set to at least the 4 setting.

Somehow I do get the feeling that I am overthinking this to a degree, but that’s how my crazy mind works.  As a Chef by trade, I want to know what is happening and why.

17

You aren’t over thinking it.  “Measure twice, cut once” as the saying goes.  It’s good to do trial runs with new equipment before you have a half day’s labor depending on it to work correctly.  The main difference between your water test and the actual fermentation will be the heat created by fermentation, so your freezer will cycle more often.

18

My point is about the temperature of the freezer when the fermentation temp controller turns the freezer off.  Do you want the freezer to be 40F, 20F, 0*F, etc?  If it is 0 *F, the fermenter temp will drop significantly below the desired temp.  The OP says it drops 3 *F below his setpoint.  Of course the temp undershoot also depends on the mass of the freezer versus the mass of the beer.

19

I don’t think you are over thinking this, some of the other respondents may be. You have 2 thermostats, both of which "make’ when the temperature of the medium they are measuring exceed their set point. The freezer thermostat is sensing the temp of the air in the freezer, the other controller is primarily sensing the temp of the outside of your fermenter. Since the compressor will only run when both controls are calling for cooling one of the controls is redundant, but the two are NOT working against each other. The reasons for adding the extra controller are twofold, you are only concerned with the temp of the beer in the fermenter and not the air temp in the freezer, and freezer temp controls, especially in inexpensive chest freezers, are not capable of maintaining the temperature range you desire. Since both controls must be calling for cooling for the compressor to run, and you want to control this with your add on, then you want the freezer temp control to always be calling for cooling. I doubt that it really matters what you set the freezer temp control at as long as it is in the “on” position. Most freezers even on the highest temp setting are below 30 degrees, but you can determine that rather easily before you put valuable beer in there.
  I think you might be better off once you have fermenting beer in there with the sensor NOT controlling compressor operation off of the temp of the outside of the fermenter, but rather the actual air temp of the freezer. Remotely monitor the temp in your fermenter AND the temp inside the freezer, and lower the set point on your controller, if necessary, by the difference between actual beer temp and your desired temp. I think you’ll get less overshoot and temp fluctuation this way. I will spare you all a long, drawn out attempt to explain my reasoning here.
  Good luck.

20

Question about 2) response above: Do you have your temp probe in the air or in a container with thermal mass? I moved my probe to a half gallon container with a thermowell. The probe is placed approximately in the middle of half gallon of water that’s in there. I have a chest freezer/kegerator. I started with a 2 deg differential but have since moved to a 1 degree differential. My target is 37 degrees for conditioning. Hope I’m not burning out the compressor that much more quickly. The cycling seems fine so far.