Inkbird not cooling to target temperature

[Nexus555]

Hey all,

I bought a Magic Chef chest freezer and an inkbird the other day for my future fermentation chamber. I have the probe dangling in the freezer and it is set to 67 degrees. For some reason, it always seems a few degrees cooler in the freezer. Right now it's at 64.2. Why is it over cooling the chest freezer?

Settings:

Temperature set: 67
Heating differential: 1 F
Cooling differential: 1 F
Compressor delay: 5 minutes

 

[day_trippr]

Chest freezers are notorious for over-shooting the cooling cycle, as there's a long lag between the thermostat shutting off the compressor and the contents of the evaporator reaching equilibrium. The effect becomes most pronounced with a totally empty freezer, while a full freezer will have the thermal mass to smooth out the average temperature. Dangling a probe inside an empty cabinet will show the worst effects...

Cheers!

 

[Nexus555]

Chest freezers are notorious for over-shooting the cooling cycle, as there's a long lag between the thermostat shutting off the compressor and the contents of the evaporator reaching equilibrium. The effect becomes most pronounced with a totally empty freezer, while a full freezer will have the thermal mass to smooth out the average temperature. Dangling a probe inside an empty cabinet will show the worst effects...

Cheers!

Makes sense. Mind if I ask a few more questions?

1.) Would a 5 gallon batch of fermenting beer help with better temperature control?

2.) Where should I place the probe? Should it dangle, be taped to the carboy or placed in a bottle of water?

3.) I've never seen it drop below 64 degrees. Even if it did vary 3 degrees to the low side, would it matter much with my beer results?

4.) My freezer setting is on 2. What setting should this be set to and would that help by adjusting the freezer setting?


Thanks again!

 

[day_trippr]

1 - the greater the thermal mass inside the freezer, the "flatter" a temperature plot will be, slowing the turn on/turn off temperature transients - at least as measured via the chamber air temperature. An empty freezer will exhibit the sharpest transitions, while a totally full freezer will take a lot longer to cool down and warm up.

2 - This has been the subject of numerous discussions here and elsewhere Some swear by dangling the sensor in a soda bottle filled with water, some use thermowells, and I advocate pinning the temperature sensor to the side of the fermentation vessel (assumes a single wall/uninsulated fermentor) with plenty of insulation applied atop to eliminate any effects from the chamber air temperature acting directly on the sensor.

3 - Short answer: most likely no effect would be noticed.

4 - Most freezers only know how to chill from below freezing temperature to WAY colder than that (like 0 to -15°F). So it rarely makes a difference where you set the temperature control when using a freezer for fermentation. But to avoid unexpected behavior, I set my freezer to its coldest setting and let the external controller manage it...

Cheers!

 

[Nexus555]

1 - the greater the thermal mass inside the freezer, the "flatter" a temperature plot will be, slowing the turn on/turn off temperature transients - at least as measured via the chamber air temperature. An empty freezer will exhibit the sharpest transitions, while a totally full freezer will take a lot longer to cool down and warm up.

2 - This has been the subject of numerous discussions here and elsewhere Some swear by dangling the sensor in a soda bottle filled with water, some use thermowells, and I advocate pinning the temperature sensor to the side of the fermentation vessel (assumes a single wall/uninsulated fermentor) with plenty of insulation applied atop to eliminate any effects from the chamber air temperature acting directly on the sensor.

3 - Short answer: most likely no effect would be noticed.

4 - Most freezers only know how to chill from below freezing temperature to WAY colder than that (like 0 to -15°F). So it rarely makes a difference where you set the temperature control when using a freezer for fermentation. But to avoid unexpected behavior, I set my freezer to its coldest setting and let the external controller manage it...

Cheers!

Perfect. Thanks!

 

[jerrylotto]

Put a muffin fan in the freezer that runs 24/7 when the controller is plugged in. It helps to even out the temperature and puts out a little bit of heat to balance out the compressor when it's shut off. I taped mine to a right angle elbow so it collects from the bottom and blows the warmer air up. The other thing I did was I cut off the probe and put a quick disconnect in place. They're NTC 10K probes so I got a couple of them and I typically plug the controller into the thermal well of my fermenter thereby controlling the temperature of the wort not the freezer. I don't care if ambient swings widely as long as my fermenting wort stays within the desirable range.

 

[homebeerbrewer]

I agree with @day_trippr, I tape my probe to the side of my fermenter. Using a thermowell would probably be more ideal, but using a freezer with temp control in a thermowell only measures the internal temp of the volume of liquid. The outer edges could get too cool. During active fermentation, that may not be an issue, but once the yeast start to settle down and stop generating heat, it could become an issue. Also, using a separate, smaller vessel, with water to put the probe in is only measuring the temp of that vessel. The smaller the vessel, the wider the temp swings will be. Similar to an empty freezer.

One last thing, when you tape your probe to the side of your fermenter, set your temp to the lowest temp in the yeast's optimal range. The center of the fermenter could be 5, or more degrees higher than the outer edge.