How do I best stabilize fermenter temp?

[MC_McMic]

Hello there, this is my first real post outside of the intro forum. I just purchased a GE 7.0 cu ft chest freezer and a Johnson Controls A19 temp controller. I intend to use them to first ferment two five-gallon batches, and then to store the beer once it's ready to drink. So, at least for now, the chest freezer will act as both my fermenter and keezer. My question is this:

Should I be putting the "remote sensor bulb" from my temperature controller in a water bath inside the freezer or just kind of hanging it in there? What is the best way to ensure the wort is being held at a nice steady temperature as opposed to a constant up and down?

 

[ifnotuthenwho]

With my freezer used as a fermentation chamber, I put the temperature probe on the side of my carboy with a piece of foam rubber over it. I hold it all in place with a couple of bungie cords. That way, I believe, I am tracking the temperature of the beer vs the air temperature.

 

[MC_McMic]

Another thing I noticed was that the instructions that came with the temperature controller advise you to set your fridge/freezer's thermostat to "the coldest setting". Why would you want to do this? I would think you would want a mild cooling so as not to overshoot your target temp when the freezer switches on.

 

[ifnotuthenwho]

This will ensure that the freezer actually comes on when the temperature controller wants it to come on, and will turn off when the temperature controller wants it off. Also, the freezer's thermostat does not control the rate of cooling, the compressor is either on or off.

 

[MC_McMic]

This will ensure that the freezer actually comes on when the temperature controller wants it to come on, and will turn off when the temperature controller wants it off. Also, the freezer's thermostat does not control the rate of cooling, the compressor is either on or off.

Interesting. That makes sense, thank you.

Sounds like the freezer has its own temperature controller, and I'm just overriding it with the Johnson Controls device, which has a higher range of temps.

 

[ifnotuthenwho]

That is exactly right. Your freezer thermostat would not allow you to maintain a temperature of 60 degrees for fermentation.

 

[Jps101]

I personally put the bulb in a jug of water. I think this is a much closer representation of what is happening within the fermenter/keg than just air. Air has no real thermal mass. Personal opinion.


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[MC_McMic]

I put a glass of water in the fermenter this morning (starting temp of around 75°, measured with a Thermapen). I'm going to see if it's at the target temp when I get home from work. If not, I'll try placing the bulb in a jug of water.

Up to this point the fermenter seems to be running a little cold and fluctuating quite a bit. I have my temp controller set to 68°, and the temp in the fermenter is anywhere between 60-65°. I'm thinking that putting the bulb in some water might be the way to go.

 

[masonsjax]

Fermentation generates heat. If you have the bulb in a separate container of water, your beer is certain to be warmer during fermentation. The bulb should be attached and insulated on the side of your fermentor, or submerged in the wort using a thermowell.

 

[kombat]

Are those black plastic/rubber thermoprobes that come with an STC-1000 waterproof?

 

[MC_McMic]

Fermentation generates heat. If you have the bulb in a separate container of water, your beer is certain to be warmer during fermentation. The bulb should be attached and insulated on the side of your fermentor, or submerged in the wort using a thermowell.

More good advice, thanks.

How exactly does a thermowell work, and how does it work in conjunction with a temp controller?

 

[masonsjax]

Stc-1000 was designed as an aquarium controller so yes, it is waterproof.

A thermowell is just a stainless steel tube, crimped on one end that you submerge in the wort through a drilled stopper. The temperature sensor for a thermometer or temp controller goes inside so you can accurately monitor the beer temp.

 

[IslandLizard]

Are those black plastic/rubber thermoprobes that come with an STC-1000 waterproof?

Yes they are waterproof but not wort/beer/alcohol proof. I read someone had it immersed into beer for a week or so and it got all gummy, looked like it was dissolving.

 

[opiate82]

I tape my probe directly to the side of the fermenter, using a folded up paper-towel between the probe and the tape to act as an insulator. Works very well. As others have pointed out, a separate jug of water that you submerge the probe in won't work since fermentation generates its own heat.

For that particular temp controller (Johnson A19) make sure to verify the temperature. I use that same controller for my kegerator but discovered the temp I set the dial to is a couple of degrees off from the actual temp inside my kegerator.

 

[MC_McMic]

I checked the temp controller by leaving the probe in a jug of water overnight, with the temp set at 68°. I, again, got a reading of 61° on the Thermapen, which is right around the same temp I was getting with the probe just dangling in the freezer. So, it's a good 7-8° off.

 

[Kate00]

Search for a thermowell on more beer . Com. They work great and are not too expensive. I think I paid 30 bucks. You need to control the temperature of the beer INSIDE the fermenter. This accomplishes that.

Fermentation temps can go way above ambient temps that water jugs etc would measure.


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[MC_McMic]

Search for a thermowell on more beer . Com. They work great and are not too expensive. I think I paid 30 bucks. You need to control the temperature of the beer INSIDE the fermenter. This accomplishes that.

Fermentation temps can go way above ambient temps that water jugs etc would measure.

Yeah, I understand that now. I'm just trying to figure out exactly how far off the dial is on this temperature controller.

I could understand ±2-3°, but 7°? That's shoddy.

 

[masonsjax]

My Johnson controller is way off too. I use that one on my keezer, so I just adjusted until pints of beer were at my desired temp and left it there. I just built an STC-1000 for my ferm chamber. That's a bit more accurate.

 

[BigFloyd]

On the question of where to put the probe to read fermentation temp, it's already been answered. Simultaneous readings taken using a probe in a thermowell stuck into the middle of the vessel vs. one taped to the side and insulated have yielded an insignificant +/- 1.0*F difference.

If you think about the geometry of a cylinder, there's a greater volume of beer around the outside of the fermenter than in the very middle, so taping to the outside and insulating provides a very accurate idea of the temp for the overall volume of liquid. There's no need to submerge anything into the liquid.