Help evaluate (improve?) my fermentation setup

[TxBigHops]

I recently bought an immersion chiller and saw how another member here used it to automate temperature control in a swamp cooler setup. So I purchased an Inkbird temp control unit and assembled a similar configuration. If you want to see pics and more details, see this thread. To summarize, I have a Big Mouth Bubbler submerged in water inside a 10 gallon round Igloo cooler. Another cooler holds the immersion chiller in an ice bath. The immersion chiller is connected to a pump which circulates the water from the Igloo, through the chiller, then back into the Igloo. My first two batches with this setup I placed the temp sensor directly into the water in the Igloo, and it seemed to work well. However, I was never sure of the exact temperature of the fermenting beer.

To improve this system, I purchased a 16 inch thermowell, and a two hole top for my carboy. This way, I know the exact temp of the beer, not the water. So here is the problem: The Inkbird is set to 62 degrees, with a 1 degree differential. (The lowest differntial allowed) I wish I could set it to 0.5 degrees, but I can't. Once the beer warms to 63, the pump kicks on to begin cooling the water surrounding the carboy. It's running quite a bit longer than before when I was just measuring the temp of the water. It takes quite a while for the temp of the beer to start dropping - 5-10 minutes. By the time the beer has finally dropped in temp to 62 and turned off the pump, the water in the Igloo is down in the low 50s, and the beer keeps on cooling for another 30 minutes, finally stopping around 60 degrees.

So, question #1: Is this okay for the beer temp to vary by this much? When set at 62, beer is going from 63 down to 60, then slowly rises back to 63, then the process repeats. Is this temp flucuation harmful in any way?

If answer to #1 is that flucuation is not desireable, am I better off measuring the water like I did before? I could perform some tests to determine the differential between water temp and beer temp, and adjust my settings so that I keep the beer temp more stable. I wouldn't always know the exact beer temp, but I think the pump would run more often, in shorter bursts, and would keep the beer temp in a tighter range. (maybe?)

As a side note, the beer is fermenting like crazy, only 30 hours after pitch, and the Bubbler is almost completely full of krausen. I just took off the airlock and hooked up a blowoff tube. If it ain't broke, don't fix it??? RDWHAHB?

 

[TxBigHops]

The Inkbird is set to 62 degrees, with a 1 degree differential. (The lowest differential allowed) I wish I could set it to 0.5 degrees, but I can't.

Well, I poked around in the Inkbird instructions, and if I use C instead of F, I can reduce the differntial to 0.3 C which is pretty close to 0.5F. So I reset to 16.7 C. But it's still cooling down to around 15.8 C (60.4 F) from a high of 17.0 C (62.6 F) So a little better at just over a 2 degree F flucuation. CO2 bubbling has reduced a bit from this morning's vigorous ferment, so I bumped it to 17.0 C. (62.6 F)

 

[augiedoggy]

Another suggestion as a workaround to your issue would be to buy some cheap discharge hose such as this http://www.ebay.com/itm/330900552367?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
They sell it at the home depot too... and wrap it around your carboy with a rubber stopper and a small piece of tubing inserted as a nipple to attach smaller hose running to your cooling coil... This way the hose will drain and and what remains will stabilze to the temp of the carboy in a short period of time. I do this with one of my conicals and it works great.

 

[TxBigHops]

Another suggestion as a workaround to your issue would be to buy some cheap discharge hose such as this http://www.ebay.com/itm/330900552367?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
They sell it at the home depot too... and wrap it around your carboy with a rubber stopper and a small piece of tubing inserted as a nipple to attach smaller hose running to your cooling coil... This way the hose will drain and and what remains will stabilze to the temp of the carboy in a short period of time. I do this with one of my conicals and it works great.

So are you saying that you think it is an issue? What do you think an appropriate flucuation in the beer temp during fermentation should be?

 

[m00ps]

Usually you want a stable fermentation temperature with a slight increase towards the end of fermentation. I usually have my beers in my chamber for 7 days or so, then take them out to make room for the next ones. After that, they warm to room temp ~68F

But also keep in mind that if the inside of the chamber changes a few degrees, it will take the wort a lot longer due to its thermal mass

But keeping a stable temp is as important as the temp itself IME. The only time I had a fusely, solvent, rubber band aid mess was from daily temps swings of 5deg or so going up and down with the Sun

 

[augiedoggy]

So are you saying that you think it is an issue? What do you think an appropriate flucuation in the beer temp during fermentation should be?

I have mine set to fluctuate with one degree variance and the most I ever see it wander is 1 degree up or down from the setpoint. I could easily narrow that with my stc 1000+ settings but I find its good enough the way it is... I put the temp probes in the center of my conicals. as m00ps mentioned at the end its good to ramp up prior to cold crashing to give the yeast a bosst so they may clean up after themselves if I remember right... my stc1000+ units have programmable yeast profiles that allow stages and ramp ups to happen as well as cold crashes...

 

[TxBigHops]

Usually you want a stable fermentation temperature with a slight increase towards the end of fermentation. I usually have my beers in my chamber for 7 days or so, then take them out to make room for the next ones. After that, they warm to room temp ~68F

But also keep in mind that if the inside of the chamber changes a few degrees, it will take the wort a lot longer due to its thermal mass

But keeping a stable temp is as important as the temp itself IME. The only time I had a fusely, solvent, rubber band aid mess was from daily temps swings of 5deg or so going up and down with the Sun

I have mine set to fluctuate with one degree variance and the most I ever see it wander is 1 degree up or down from the setpoint. I could easily narrow that with my stc 1000+ settings but I find its good enough the way it is... I put the temp probes in the center of my conicals. as m00ps mentioned at the end its good to ramp up prior to cold crashing to give the yeast a bosst so they may clean up after themselves if I remember right... my stc1000+ units have programmable yeast profiles that allow stages and ramp ups to happen as well as cold crashes...

Sounds like I need to go back to my previous method of controlling the water temp and just monitoring the beer temp. I won't know for sure until I test it and take some measurements, but I believe that the beer temp was more stable when the water temp was only fluctuating 2-3 degrees.

So m00ps, I assume you are using an air cooled chamber, but are monitoring your beer temp as I am. Let's assume you set your temp controller to keep your beer at 62. It warms up to the point where your cooling source turns on and cools your beer back to 62, then shuts off. I assume the air temp at that moment is considerably below 62. Doesn't your beer also continue to cool until some point at which the beer and air temps stabilize somewhat close to each other? Does this happen much more quickly with air than it does with water? How far below 62 would your beer temp go before it stabilizes and begins to rise again?

augie, I'll have to think about how I would make your discharge hose suggestion work with my equipment. But you say that you flucuate as much as 1 degree high to 1 degree low, or a total of 2 degrees. I'm currently going from 0.6 degrees above to 1.6 degrees below, so a total of 2.2 degrees, virtually the same as you since I switched from using farenheit to celcius. Not sure it's worth revamping the system for 2 tenths of a degree.

 

[augiedoggy]

correct but thats because I have my stc set for 1 degree of variation.. it doesnt kick on until the temp wanders 1 full degree from set point. I somehow misread your original post and thought you had more variance.

 

[TxBigHops]

correct but thats because I have my stc set for 1 degree of variation.. it doesnt kick on until the temp wanders 1 full degree from set point. I somehow misread your original post and thought you had more variance.

I did have about 3 degrees of variance in the first post. Second post I switched from F to C and that tightened it a bit.

After some quick testing this morning, I found that once the temp difference between the water and beer had stabilized, they both measured exactly the same temperature. So I decided to move the Inkbird probe back into the water. I returned the scale to F, since I'm more comfortable using that scale, and bumped the set temp slightly from 62.6 (17.0 C) to 63, as the fermentation activity has begun to slow. The differential is back to 1 degree, and the beer measured 62 at the time of the move. It's pretty cool in Houston today, so I suspect it will take most of the day to slowly rise to 64 before kicking the pump back on and dropping it back to 63. I left the thermowell in the carboy, so I will do some more testing tonight to confirm that the beer and water temps reamain relatively close. I'm concerned that only a 1 degree drop in the water temp may not be enough to cool the beer much at all. I may need to change the set temp to 62 and use a 2 degree differential.

 

[FuzzeWuzze]

So m00ps, I assume you are using an air cooled chamber, but are monitoring your beer temp as I am. Let's assume you set your temp controller to keep your beer at 62. It warms up to the point where your cooling source turns on and cools your beer back to 62, then shuts off. I assume the air temp at that moment is considerably below 62. Doesn't your beer also continue to cool until some point at which the beer and air temps stabilize somewhat close to each other? Does this happen much more quickly with air than it does with water? How far below 62 would your beer temp go before it stabilizes and begins to rise again?

Yes the air will stabilize quite a bit faster than water would...this is also what the BrewPi attempts to fix. Using PID its able to more accurately shut off your fridge early so that the remaining cold air brings your beer up to its set point as the air warms towards your set point.

You'll always have a bit more variation using a STC1000 or the like but its pretty minimal, although i'd think if your using a modern chest freezer or something else that gets VERY cold VERY fast(my keezer can get to like -20F) and holds its temperatures for long durations you'd probably also need some sort of heat source or else the problem you described would be quite extreme...in a fridge or mini fridge that only gets to the low 40's though its not a big deal.

That said once the krausen has fallen and your fermentation has started to slow to a halt it never hurts to let it rise up to 68-70F to let the yeast keep going, they can usually clean up the beer a bit and maybe squeak out another gravity point or two.

 

[TxBigHops]

Thanks for contributing @FuzzeWuzze.