Fermentation Chamber Help

[BOB357]

It is perfectly normal to overshoot temperatures when the wort is still, as in cooling down 10 or 15 degrees to pitching temperature or cold crashing. I set the controller 3 or 4 degrees higher when cooling down and use ambient temperature for crashing, both with good results. The thermowell works great otherwise.

 

[Nosybear]

I use a 16oz plastic Coke bottle filled with water. I have a 1/4" hole drilled in the cap. I leave my temperature probe inserted in the bottle. The water in the bottle will change quicker than the temperature in the fermenter. The bottle temperature will change 2 degrees before the temperature changes in the fermenter. So the bottle temp will have swings of 4 degrees but the temp of the fermenter remains constant.
Also for the heating I use a little 5 watt bulb on an extention cord inside my chest freezer. Cheap and it provides all the heat i need.

That's a good solution, too.

 

[Zak2428]

Thanks everyone for the insight/ideas - I truly appreciate it! This is the first I'm hearing of a Thermowell, so I'm going to get one of those and also try just taping the sensor to the side of my fermenter and see which works best for my set up!

Thanks!!

 

[Nosybear]

Thanks everyone for the insight/ideas - I truly appreciate it! This is the first I'm hearing of a Thermowell, so I'm going to get one of those and also try just taping the sensor to the side of my fermenter and see which works best for my set up!

Thanks!!

A thermowell is just a sealed stainless steel tube that holds the thermometer probe, either permanent or temporary.

 

[BarbarianBrewer]

On the other hand, if you use the thermowell, temperatures will yo-yo. Reason: The probe is in the center of the beer and (oversimplified, omitting convection) the beer warms and cools from the outside in. The effect is more pronounced with a freezer that cools faster than a refrigerator. Ask me how I know....

Probably the same reason I know. I froze my first attempt at a lager. I had the same setup in @Nosybear's example: A temp probe in the middle of the beer and fermentation chamber was a chest freezer. I set the temperature controller to 33F/1C and checked it a few days later. The carboy was mostly frozen! I expect that by the time the temp probe read 33F that the ambient temp in the chest freezer was way below freezing. So even thought the controller shut off power to the freezer, the beer kept cooling. Since then I tape the temp probe to the side of the fermentation vessel and cover it with a bit of styrofoam.

 

[GFHomebrew]

Probably the same reason I know. I froze my first attempt at a lager. I had the same setup in @Nosybear's example: A temp probe in the middle of the beer and fermentation chamber was a chest freezer. I set the temperature controller to 33F/1C and checked it a few days later. The carboy was mostly frozen! I expect that by the time the temp probe read 33F that the ambient temp in the chest freezer was way below freezing. So even thought the controller shut off power to the freezer, the beer kept cooling. Since then I tape the temp probe to the side of the fermentation vessel and cover it with a bit of styrofoam.

It equalizes eventually .

 

[Nosybear]

It equalizes eventually .

True that, too.

 

[Donoroto]

Is that thermowell1.5" in diameter or 1.5" long?

1.5" is the nominal diameter of the tri-clamp fitting; it is about 8" long and sits 12 inches below the 'waterline' (wortline?), being inserted into the side of my Stainless Steel fermentor. So it has excellent contact with the center of the wort volume.

Tape the probe to the outside of the fermentor covered with a bit of insulation

Exactly what I have been doing after one try with the (extra-cost) thermowell. I have a piece of 1/4" felt over it, and that configuration gives good results.

 

[Bubba Wade]

There are a few things to keep in mind when controlling temperature.

The first thing to consider is the nature of the thermal system itself. Per volume, the heat capacity of water is approximately 3200 times more than the heat capacity of air. Taking the example of a 5 cu ft freezer with a 5 gallon batch, we have approximately an 8:1 ratio of air to wort. So the heat capacity of the wort is about 400 times the capacity of the air. Cooling the air temperature by 10 degrees and letting the system come to equilibrium will only lower the wort temperature by 0.025 degrees. So if we cycle the freezer based on air temperature, it will cycle many times before the wort temperature falls by 1 degree, depending on the deadband setting of the controller.

Now if we measure the temperature of the wort, either on the insulated surface of the fermenter or using a thermowell, the temperature of the wort will move very slowly, even if the air in the freezer goes below zero, due the differences in thermal mass. And once the temperature of the wort reaches the target temperature, the air will quickly warm up due to the low heat capacity. I am simplifying this a bit, because the inside surfaces of the freezer also have some heat capacity. However, in most cases these are still pretty small in comparison to the heat capacity of the wort.

@Brewer Jim uses the Coke bottle of water as a thermal mass. This is not a bad compromise. It's a smaller thermal mass, so the freezer will cycle more often than taping the probe to the fermenter, but not nearly as often as leaving the probe in open air.

Now, if you are using a glycol system with a cooling coil in a fermenter, the dynamics change significantly. The glycol/water solution has approximately 90% of the heat capacity of water, depending on the concentration and temperature. It is easier to overshoot temperature with this system and placement of the temperature probe is a bit more important.

Hopefully this information is useful without being too full of engineering and physics.

 

[Hawkbox]

I have the thermowell in the SS brewbucket too, I just stuff the inkbird probe in it, set the temperature and walk away for as long as needed to get to temperature. I have a little mini fridge that isn't to powerful so no freezing issues. The beer temp doesn't swing much in my experience with my setup.

I have a heat source too but for that I pull the probe out and just leave it in the air, I'm fine with it taking longer to heat up. Just don't try to run both off the same probe or it's gonna be all over the map.

 

[Zak2428]

So here's an issue I think I'll run into... I bought a 7 Cu Ft Chest Freezer because I figured I could fit 3 fermenters in there, brew more beer at one time, live a happier life. However, I have a feeling now that putting 2 glass fermenters and 1 plastic bucket in there at the same time, the beer wont maintain the same 65 degree's throughout each vessel... And here's why I'm thinking this:

I tested my set up with a 1 gallon glass fermenter. I've had it set up to maintain a liquid temp of 65 degrees (taped the probe to the side of the fermenter and also had a thermometer inside it to get the real liquid temp) - they both registered very close to 65. I just swapped out the 1 gallon glass fermenter with my plastic bucket (primary ferm) filled with 2 gallons of water; taped the probe to the side and threw the thermometer in the bucket - both say 65, HOWEVER the air temp in the freezer is significantly colder. This is obviously not ideal because if glass will transfer that cold air to the liquid more readily than the plastic bucket, I wont actually be able to ferment 3 fermenters in there at once unless I do a bit better planning with the yeast and ensure the yeast that needs the colder temp is in the glass and not the bucket. Has anyone ran into this problem? @Bubba Wade Sounds like maybe something you've considered with your science background. it's also possible that the 1 gallon of extra water in my primary fermenter is requiring more energy from the freezer though. I'm no science expert...

Either way, tomorrow i'm going to test it out with both fermenters in there (plastic and glass). Keep the probe taped to the plastic bucket and drop the thermometer back in my 1 gallon glass ferm and see what happens. My guess though is the bucket will sit at 65 and the glass ferm will drop much lower to 55-60ish.

 

[Hawkbox]

I've honestly never tested the thermal capacity of anything I work with as I only have the ability to chill one fermenter at a time.

 

[Bubba Wade]

Either way, tomorrow i'm going to test it out with both fermenters in there (plastic and glass). Keep the probe taped to the plastic bucket and drop the thermometer back in my 1 gallon glass ferm and see what happens. My guess though is the bucket will sit at 65 and the glass ferm will drop much lower to 55-60ish.

Let's take your scenario of a 1 gallon glass fermenter and a 2 gallon plastic fermenter. First of all, the vessel material won't matter that much. Glass has a higher thermal conductivity than polyethylene, but not that much. The limiting factor for heat transfer in either case will be natural convection. If there is no exothermic reaction in the wort, both vessels will equalize at very close to the same temperature, if the freezer/fridge is pretty well insulated.

However, during fermentation, yeast activity is a bit exothermic. During peak fermentation, it appears that a 5 gallon batch of wort can produce around 5 watts of energy released in the form of heat. So, your two gallon batch may peak around 2 watts.

I think you can ferment your two 1-gallons vessels in the same chiller as your 2-gallon vessel. The two gallon fermenter may be marginally warmer, but you shouldn't see much difference between the two sizes. I would go ahead and tape the probe to the outside of the 1-gallon glass fermenter and use that as the measurement for the controls.

 

[Zak2428]

Let's take your scenario of a 1 gallon glass fermenter and a 2 gallon plastic fermenter. First of all, the vessel material won't matter that much. Glass has a higher thermal conductivity than polyethylene, but not that much. The limiting factor for heat transfer in either case will be natural convection. If there is no exothermic reaction in the wort, both vessels will equalize at very close to the same temperature, if the freezer/fridge is pretty well insulated.

However, during fermentation, yeast activity is a bit exothermic. During peak fermentation, it appears that a 5 gallon batch of wort can produce around 5 watts of energy released in the form of heat. So, your two gallon batch may peak around 2 watts.

I think you can ferment your two 1-gallons vessels in the same chiller as your 2-gallon vessel. The two gallon fermenter may be marginally warmer, but you shouldn't see much difference between the two sizes. I would go ahead and tape the probe to the outside of the 1-gallon glass fermenter and use that as the measurement for the controls.

Makes sense. Thanks, I'll give that a try tomorrow.

I spent the day with the probe taped on my plastic fermenter with 2 gallons of water in it and the 1 gallon glass fermenter with the thermometer in it and, to my surprise, the glass fermenter has been sitting closer to 70 degrees and my plastic bucket (using the thermometer) is sitting around 65. Inkbird is set to 65 (probe says 66.5), Hd & Cd set at 2 degree's.