Dual Stage Temp Controller Issues

I'm using a dual stage temperature controller with a carboy thermowell to control my chest freezer/ heat wrap during fermentation, but have run into temperature control issues.

The problem is by the time the cold or heat gets to the thermowell inside the carboy, the ambient temp inside the fridge is way too cold or way to hot. Then when the set temperature is hit and the cold/ heat is turned off, the temp continues to fall or rise because the ambient temp is so cold/ hot. There is quite a lag between the time the ambient temp gets to the right temperature vs the temperature inside the center of the fermenting wort in the carboy. I am having huge temperature swings back and forth.

Does anyone have suggestions to deal with this problem?

Are you saying the air temp is swinging or the ambient temp? If the air temp is fluctuating, that's irrelevant so long as your beer temp remains constant. You're fermenting beer, not air right?

If your beer temp is fluctuating because of this, consult the manual. Some controllers have a delay setting that keeps your compressor from cycling too often.

I'd also check the differential. Some controllers have a temp differential you can manually set to keep fluctuations to a minimum

The beer temp is swinging. The issue is that there is a time lag between the ambient temp and the temp of the beer. By the time the core temp of the beer in the carboy hits my desired/set temp, the ambient temp in the freezer is much colder because the freezer had to run until the beer temp caught up with the ambient temp. The thermowell is sitting in the center of the carboy so it takes some time to for that cold air to reach it. Then when the desired temp of the beer is reached and the controller shuts the freezer off the beer continues to drop because the ambient temp is so cold due to the time lag. This continuation off a drop in temp results in setting off the heater. The freezer and heater end up fighting each other and causing the temp to swing wildly back and forth.

What I tried to do recently was not place the temp probe in the thermowell but instead outside of the carboy to measure the ambient temp and try and find a balance between the ambient temp and beer temp. I also turned my freezer control knob as low as possible so that it doesn't get ridiculously cold super fast because the beer temp needs some time to catch up to the ambient temp.

You could try placing the probe in a glass/jug of water so that it stays more consistent. Depending on the size of the glass/jug of water, it should keep the temps aligned better with what you are wanting.

I also have a thermometer in a glass of water on its own, just to verify the temperature is where I want it, then adjust the temperature controller if need be.

I tape the sensor to the outside of my fermenter and then insulate with bubble wrap. I don't have this issue. I also have my controller tolerance set to 0.7*C.

Are you pitching at or below your ferment temp? If you are pitching warmer, you can experience this sort of problem.

I also use a thermowell, but I only use a single stage temp controller (set to cooling).
I have no problems providing the temperature differential is within one or two degrees of the set point, but I do have a problem if the differential is significantly larger.
I get around this problem by positioning the temperature sensor within the thermowell.
I start by positioning the sensor at the bottom of the thermowell, and wait for the reported temperature to stabilize. If the temperature difference is greater than about 2 degrees, then I move the sensor to the top of the thermowell, where the temperature is equal to the ambient temperature, but still influenced by the wort temperature, by convection.
By the next morning the temperature of the wort has always dropped to within one degree of the set point, and I then position at the bottom of the thermowell, where I leave it until fermentation has completed.

-a.

BigFloyd said:

I tape the sensor to the outside of my fermenter and then insulate with bubble wrap. I don't have this issue. I also have my controller tolerance set to 0.7*C.[...]

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Similar here. I have two beer fridges, one equipped with a heater for winter fermentations, and a keezer, all of which run on external controllers with probes strapped to carboys or kegs. I run a 1°F differential on all of them, and never have an issue with beer temperature overshooting...

Cheers!