Freezer too cold even with temp controller

[HopMantis Brewing Co]

So I have an InkBird temp controller for a new chest freezer I picked up. I ran a test on it with the temp controller and the temp continues to drop long after the shut off. I have the probe in a bottle of water. As a test set temp, I set it at 38F with a diff of 1. It cuts off when its supposed to but the temp continued to drop to 31F. The reason I chose this InkBird is because it accepts both a cooling and heating device simultaneously and switches between the two to help maintain the temp. My concern is if I cannot stabilize the temps on just the cold side within a few degrees, the wort may get too cold to even begin the fermentation to produce any of its own heat. Suggestions, folks?

 

[jeffpn]

My fermentation chamber is typically set to 55°. It runs in about an 8 hour cycle. After the freezer cuts off, it continues to chill as you describe. Then the fermwrap kicks on when it hits the low point. It warms back to the set temp. The fermwrap shuts off, and temps drop a second time to the point where the fermwrap engages again. After that, it doesn't drop to the low point, but it does drop. Then the temps slowly rise until the freezer turns on again. That freezer is designed to chill air far below freezing. That's what you're dealing with. The fuller you have the freezer, the less of a problem you'll have.

 

[EbonHawk]

I don't get that with my setup. Is that something in the design of the newer freezers? Mine is like 50 yrs old, maybe older, and it kicks on when the setpoint+2° is reached and it drops down to the setpoint and cuts off. When the temp rises 2°, it kicks on again and drops the temp back down to the setpoint again. I have mine set to a 2° variance, so it's working like it's supposed to. I've never measured how long it stays on, but I don't think it's very long really, maybe 30 minutes, then after a few hours it kicks on for another 30 mins.

 

[jeffpn]

It kicks off when it reaches the set point, but the cold air in the cabinet continues to chill the beer below the setpoint. Does your controller display the actual temperature? I'd be surprised if the same thing isn't happening to you. Freezers make some pretty cold air!

I would bet that the phenomenon would be less pronounced if the proble was just in the cabinet, instead of in a bottle of water. I think the bottle makes temps more stable, especially when opening the lid. That's the way mine is set up as well. Actually, mine is in a well in the beer itself.

 

[oliver]

i use ink bird on a big chest freezer, i set it at 60ºF, and it usually runs down to 58ish, and back up to 62ish when. At colder temps you'll get lower swing in temp. just have to tinker with it.

 

[EbonHawk]

It kicks off when it reaches the set point, but the cold air in the cabinet continues to chill the beer below the setpoint. Does your controller display the actual temperature? I'd be surprised if the same thing isn't happening to you. Freezers make some pretty cold air!

Hmm, I'll have to check it with an extra thermometer to be sure. But this freezer is solid all the way around the walls, there's no airflow or ducts or anything. It just cools down with coils in the walls. The probe is just suspended next to the outer wall of the glass carboy.

 

[HopMantis Brewing Co]

Thanks for all your responses, folks. I went ahead and purchased a warmer belt to put around the fermentor. As a new test, I filled a bucket with water, taped the probe to the side then covered the probe with some insulation to isolate it from the ambient temperature. Set it to 38F. Im not seeing such a huge swing like before. Its actually staying within a 2'F range (1'F above and 1'F below). I also have the warmer belt plugged in and wrapped around the bucket. It should cycle on when it passes below the setpoint by 1'F. Good to play with it now so I know its swings before I actually go to use it as a fermentor cabinet. Im planning a brew for next weekend so I should have everything in check by then. If not, I have a good ol' reliable mini fridge that'll get the job done until I can trust the chest freezer.
Cheers ~

 

[jeffpn]

My freezers work the same way, with the coils in the walls, no airflow. When the freezer is on, it's trying to make the cabinet temperature somewhere around 0°F. That's how it's designed. But you want your beer to be 38°, 55°, 68°, or whatever it is that you're doing with the freezer, depending on the stage and style of the beer. That's significantly warmer than the potential of the freezer. When the temperature reaches the setpoint, the air in the freezer is still going to be fairly close to the 0° temperature that the freezer is trying to do. And being insulated, it has the ability to stay that cold for a period of time. That air will continue to cool your beer as long as it's cooler than your beer, even though the freezer isn't running. I hope that helps to explain the point I tried to make earlier.

 

[EbonHawk]

But that's not how the thermostat controller is supposed to work.... Unless I'm missing something.. The air temp inside my freezer is 66° now (I changed the thermostat to 66°), and when the air temp rises to 68° (because of the 2° variance setting) it kicks back on just long enough to drop the air temp back down to 66° and then the controller trips and the power is cut to the freezer's compressor and the air temp starts slowly climbing back up to 68°. The air temp never gets below 66°. Where does the 0° come into play in this setup? :?

I just checked with a thermometer, and the air temp inside my freezer is 64°.

Buy, on a positive note, I now know my freezer is 2° above where I thought it was, so I thank you for that!

 

[jeffpn]

I would assume that if the probe is hanging in the air, that the air wouldn't get to far away from the set point. I guess I'm thinking about how I have mine set up, in my beer itself. So the beer is what needs to reach the set temp, not the air in the freezer. First the freezer needs to chill the air, and the air needs to chill the beer. That would be the scenario with the cold air in the freezer. In your situation, the coils will still be cold even after the power is cut off. So I assume there's a bit more chilling to go. At any rate, in my set up with fermwrap, my beer temp is stable to +/- 1°F. I'm quite pleased with it. Generally, the reason people don't hang their probe in the air of the freezer is that it will tend to turn on every time you open it up. In my new keezer (6 tap unit, not a fermentor, no fermwrap), I put my probe in a gallon of water for stability. It probably goes 2-3°F below the set point before it starts warming back up.

 

[EbonHawk]

I know some people might tend to disagree with how I have mine set up, but I think it just makes more sense as far as thermodynamics and all that. I look at it from the viewpoint of how my beer ferment temps run with respect to being in my house... The actual beer temp always ran 1 or 2 deg above whatever the current inside ambient temp was. If I had the thermostat set on the a/c to say 74, and the air temp was close to that..then my beer was always one or two deg above that, depending on fermentation activity.

So, when I switched to fermenting in my freezer for the last three batches, I basically set it up the same way as I was used to. The thermostat controller probe lying against the side of my carboy. As long as the air temp stayed fairly constant around 68°, then my beer should be fairly close to that, + 1 or 2 deg depending on fermentation activity. And that's what my thermometers have now confirmed. My beer temp was 64.7 deg in one fermenter, and 66 deg in the active fermenter. So this experiment has helped me figure out that I needed to set my thermostat controller a tad higher, because it was reading 2 deg off, and I want my beer to ferment at around 68°.

I figured the less I had to have dangling in my beer the safer the whole process would be for me, and now after watching my temps over the past couple of hours, I'm perfectly happy with knowing it's within a couple of degrees of where I want it to be.

 

[jeffpn]

Sounds good. I use a pinched off copper tube that sticks down into my beer. A 2 port rubber carboy cap holds both my tube and an airlock. That way my probe isn't directly in the beer. With that setup, it doesn't matter how much heat fermentation creates. The temperature controller keeps the beer at the set point.

If you have the probe taped to the side of the carboy and not insulated, then that's probably a good hybrid of the way I just described and hanging in the air. Im sure you're doing better now keeping temperatures stable than you were doing before. Stick with what works for you!

 

[Ozarks Mountain Brewery]

never used an inkbird but mine is a diy stc-1000, I set the high and low to turn on and off usually 1 degree both directions the main temp stays an even 34 and my probe is laying on the bottom, oh thats my keezer my fermentation chamber is the same but hanging in the air, one thing water is much slower to change temp than air is so it has to catch up, that may be what your seeing

 

[oliver]

a little drunk so i didn't read all the responses, but i saw some things about air temp? I use a 2 gal bucket fermenter filled with water, the ones with a grommet hole in the lid, and i stick my ink bird probe through that. So it's actually measuring the temperature of a liquid in the ferm chamber.

 

[EbonHawk]

a little drunk so i didn't read all the responses, but i saw some things about air temp? I use a 2 gal bucket fermenter filled with water, the ones with a grommet hole in the lid, and i stick my ink bird probe through that. So it's actually measuring the temperature of a liquid in the ferm chamber.

and that's what didn't make sense to me, when I was deciding how to set mine up... It's all about temperature stability (and knowing what that temperature is, reliably). Doesn't matter how you get there, as long as the temp stays relatively constant.

Temp probe hanging down in center of beer inside carboy... It takes awhile for the temp to stabilize all the way to the center of that mass, and the surrounding (outside the carboy) air has to drop (and will drop) well below the setpoint until that mass of beer stabilizes at any given temp. And that's what you guys are seeing with the really low air temps of the freezers (close to 0°), because it continues to drop the air temp as low as it can go, until that temp sensor inside all that beer reaches its setpoint..

If the temp sensor probe is hanging in the air next to the carboy, the surrounding temp is being held at the desired setpoint, and the beer will naturally follow along pretty closely, with a deg or two warmer inside the beer, depending on thermal exchange and heat generated by fermentation. But as long as you keep that surrounding air at or within a deg or two of your desired temp, the beer should hold within a deg or two of the surrounding air. This is the way I chose to set mine up because it seems like it would keep the beer temp fairly stable and in-line with the surrounding air. And it does. That's what I was going for. It seems to me like doing it the first way would cause huge swings in the surface temp of the beer (next to the glass, and the surrounding air being close to 0°) as the thermostat would keep the freezer on a lot longer than necessary. As my setup is, it runs for just about 30 mins to get the temp back stabilized, then it cuts off for several hours as the temp very slowly rises back up. Just seems more efficient this way, I think.

 

[jeffpn]

Just like in everything else brewing related, there's more than one way to skin a cat here. I think we all gravitate towards which method works for each of us.

 

[EbonHawk]

True, true.

 

[jeffpn]

Now you have me thinking about my setup. I still like the well idea. Instead of my well going straight down into the middle of the beer (or water jug in the case of my serving freezer), I could bend the copper tube well so that it's very close to the edge of the vessel it's in. That would more simulate being taped to the outside of the vessel. That way, I get away from the center of the liquid being the last to reach its temp.

 

[Head First]

I go with the probe hanging there against the carboy for the exact reasons described. Works for me. Fermentation vessel only gets 1-2 degrees warmer in its most active state.

 

[jeffpn]

Sounds like the same margin I have, except the other way. My beer gets 1-2°F colder than the set temp. Before I left home this morning, I bent the well I have in my serving freezer. It'll be interesting to see if that results in the low temp being closer to the set temp. It's only a 1/2 gallon jug, so it probably won't make much difference.