Fermentation Temp Rise

[Galaxy_Stranger]

Would you say that when the yeast really gets going that it raises the temp about 5° by itself?

 

[noggins]

yep. if you have temp control, setting it to the lower range of the yeast is usually a good idea for that reason. unless you use a thermowell.

 

[day_trippr]

5 degrees may be low-balling. I've read posts claiming as high as 10...

Cheers!

 

[Gavin C]

Would you say that when the yeast really gets going that it raises the temp about 5° by itself?

Fermentation is exothermic. Heat is produced. 5F rise in a 5 gallon batch easy. No problem.

That is the reason folks use methods to remove the thermal energy from the beer by removing thermal energy from the surrounding environment.

Swamp cooler, wet t-shirt and fan or a converted freezer all remove thermal energy compensating for the heat produced by fermentation.

With a chest freezer and STC1000 you can keep the beers temp maintained at your target temp +/- 0.5F. No problem.

Thermowell is not needed and is not the best way to do this. Plenty of threads discussing the science behind that one. Probe taped to the FV and insulated from ambient temps is the best way with an STC1000

Edit: The best way is probably some fancy doohickey jacketed conical with glycol coolant.

 

[Galaxy_Stranger]

I have it in the tub. When it got to 73°/74°, I filled it half-high with water and added enough ice to bring it down to 64°. Several days later, the burbling subsided and the ice went away, so now it's hanging around 68°. This is awesome because I can have 3 fermenters in there at once!

 

[shortyz]

i think the temperature rise is higher when your pitching temp and room temp is 70+. seems like the yeast go crazy and heat up the bucket fast.

 

[pdxal]

I have it in the tub. When it got to 73°/74°, I filled it half-high with water and added enough ice to bring it down to 64°. Several days later, the burbling subsided and the ice went away, so now it's hanging around 68°. This is awesome because I can have 3 fermenters in there at once!

What yeast are you using and what type of beer are you making? 73/74 may be too high.

 

[Galaxy_Stranger]

Currently, it's a Doppelbock with Ale yeast. I didn't like those numbers, so I lowered it down to 64°.

 

[pdxal]

Dopplebock is made with lager yeasts, but I'll bet it comes out tasty made your way. 64 is much better. In the future, controlling fermentation temperature is important, particularly early on in the process (pitch temp, first few days especially).

 

[Galaxy_Stranger]

Let me be clear about what was going on. The kit was put together specifically with ale yeast in mind because I can't lager. This is quite common where I live because many people in the area don't lager. Just about all kits in my area have an ale alternative. When I pitched that night, I watched the temperature which started at about 70°. Within a couple of hours, the yeast started to kick in and the temp raised up to about 73°. I then added water and some ice to the tub to cool things down, which it did. The next morning, it was at 64° and hasn't been much above 68° since.

So, my original post was to get feedback on how much active yeast can account for the current temperature of a wort batch.

 

[pdxal]

Dopplebock is a lager, so you are making something similar, but different regardless of what the kit maker says.
The temperature started out too warm at 70°, it was warm through the first part of yeast reproduction and growth so you will probably have some off flavors develop. Though, not many since you cooled it down rapidly.
Good for you that you cooled it down rapidly.
Yeast can cause a significant temperature increase. I've seen more a than 5° increase above pitch temperature and air/water bath/fermentation chamber temperature. That's why most experienced brewers will be telling you to pitch on the low end of a yeast's preferred temperature range.
Cheers.

 

[ncbrewer]

Keep in mind that a water bath transfers heat much faster than air. During active fermentation I find the beer is only about 1 degree warmer that the water bath. For some reason though, I find it stays several degrees warmer during the lag phase so I watch it closely and add ice as needed.

 

[kombat]

Thermowell is [...] not the best way to do this. Plenty of threads discussing the science behind that one. Probe taped to the FV and insulated from ambient temps is the best way with an STC1000

Please explain. I use a thermowell and an STC-1000. I'm measuring the temperature of the actual beer, right in the middle, and controlling temperatures accordingly. I regularly keep my fermentation temperature within a 0.6° C tolerance (within 0.3° C above or below target temp).

How would measuring temperature way out at the edges be better?

 

[Gavin C]

Please explain. I use a thermowell and an STC-1000. I'm measuring the temperature of the actual beer, right in the middle, and controlling temperatures accordingly. I regularly keep my fermentation temperature within a 0.6° C tolerance (within 0.3° C above or below target temp).

How would measuring temperature way out at the edges be better?

Best is such an absolute and disagreeable term.

My understanding is that thermowell usage is subject to greater over-shoot and under shooting of the temperature as the measured temperature at the center of the carboy will take longer to equilibrate with the cooler beer at the periphery closer to the cooled/warmed micro-cliamte in the fermentation chamber.

Once the central temperature reaches the target the periphery will be cooler/warmer (depending on whether heat or cooling cycle is in effect) and the beer temperature at the center will continue to drop/rise until thermal equilibrium is once again reached. The potential down side being greater instability in actual beer temps and more cycling of the compressor and/or heat source.

I guess this is the primary rationale behind the development of predictive algorithms like brew-pi designed for use with thermowells. i.e; shut off the power before set tempis reached allowing that final glide down to the set point.

During active fermentation this is less of an issue as the greater actifity and homogeneity in the wort will largely negate this issue i would think.

It sounds like you got things ironed out. I thought I read a thread (one of the threads to which I earlier referenced, I dont have the link I'm afraid) in which you yourself reported this very over/under shoot issue. Perhaps I have my wires crossed. Maybe it was the other way around and switching to thermowell solved your over/under shoot issues.

It's somewhat moot as by your data now your temperatures are as stable as mine with my insulated sensor at the periphery. +/- 0.3C (I can go back to celcius now that I'm talking to a Canadian). I certainly cannot claim better stability than that.

I know a HBT user has studied this in some depth and reported on HBT. I can't recall the user or the thread. So discount that statement should you wish to do so.

It's a topic that's been well and truly discussed at some depth. Based on my own readings of the threads and distilling out the details I benched my plans for thermowells. I do like gadgets but this one seems extra to requirements.'

As always YMMV. It's of course splitting hairs in going from one method of excellent control of fermentation temeprature to another. it is fun to split hairs though, wouldn't you agree?

 

[kombat]

During active fermentation this is less of an issue as the greater actifity and homogeneity in the wort will largely negate this issue i would think.

What you say makes sense, but I think you hit on a key point here: I'm only really concerned about the temperature during active fermentation, during which there is a great deal of movement inside the fermenter. As such, I would expect that the temperature is relatively consistent throughout the entire fermenter.

Once active fermentation subsides, I suppose you may get a bigger temperature swing, but the yeast are finished, so it seems irrelevant, in my opinion. Besides, you'd still get some degree of temperature-leveling convection. As the outsides of the fermenter cooled faster than the core, that beer would sink to the bottom, pushing beer up the center of the fermenter, where it would reach the top and spread out. I can't imagine this would happen very quickly, but it would be enough to produce sufficient mixing to avoid a temperature differential of more than a degree or two, I would guess.

During active fermentation, I'd rather err a degree or two too low than too high. As such, if I were measuring the temperature at the outside wall of the fermenter, it would read slightly low (as the beer in the middle could be slightly warmer, prematurely turning off the cooling circuit. On the other hand, if I measure the temperature right in the middle (as with a thermowell), the beer at the outer edges might get slightly colder than the target by the time the beer in the middle cools sufficiently to turn off the cooling circuit, meaning the overall average temperature of the beer is slightly lower than desired.

It sounds like you got things ironed out. I thought I read a thread (one of the threads to which I earlier referenced, I dont have the link I'm afraid) in which you yourself reported this very over/under shoot issue. Perhaps I have my wires crossed. Maybe it was the other way around and switching to thermowell solved your over/under shoot issues.

You have a good memory, I think it was indeed me you're thinking of. In that case, I was using a light bulb in a paint can as my heating source, and the temperature was getting waaaay too hot. Once I switched to a heating belt for my heat source, my temperatures stabilized dramatically.

My understanding is that the thermowell is the best way to measure temperatures. The other notable discussion on the topic I recall is in regards to immersing the temperature probe in a small glass of water inside the fermentation chamber. I believe that's widely considered to be a terrible approach, because as the yeast get active and warm up the beer, it takes time for that heat to get transferred to the surrounding air inside the chamber, and more time still to warm up the water in the cup sufficiently to finally trigger the STC-1000 to turn on the cooling circuit. By then, your beer temperature could be several degrees hotter than desired, and off flavours have likely already started to be produced.

 

[Gavin C]

Looks like we shall have to aggree to disaggree as to what the data indicates to be the "best" way to use our beloved STC1000 chest freezer combos.

I 100% agree with you with regard to sensor measuring ambient in a fermentation chamber while fermentation is occuring. Whether it is via a reading of ambient air temps or a reading from a small heat sink like a jar of water, it is a nonsense approach and castrates the effectivness of one's investment in an STC1000/fridge.

Measuring beer temperature is the key. Both of us are doing that by slightly different means.

Just to be clear I know you are not advocating for measuring ambient @kombat. On that note and somewhat related but possibly . Sorry OP

No one would avocate measuring the ambient temp of their grill when grilling a steak to a target temperature. If we measure at all, we measure the subject to which heat is being applied (the steak). Can't understand why so many folks persist with the thought disconnect in measuring ambient temps in a fermentation chamber. See it all the time in threads.

Ambient temps in a keezer/kegerator is a different beast entirely. The focus there is on miniizing cycling of the compressor while achieving relatively stable beer temps. Some measure keg temp directly. Some measure ambient, some like myself use a small heat sink (4oz jar of baking soda)

 

[kombat]

Ambient temps in a keezer/kegerator is a different beast entirely. The focus there is on miniizing cycling of the compressor while achieving relatively stable beer temps. Some measure keg temp directly. Some measure ambient, some like myself use a small heat sink (4oz jar of baking soda)

Agreed, this is a different case. I think the problem with measuring keg temperature in a keezer is that it's only measuring that one keg.

Say you have 5 kegs in your keezer, and the one to which you've attached (and insulated) the temperature probe is near-full. One of the other 5 kegs happens to be almost empty.

The full keg finally warms up enough to trigger the STC-1000 to turn on the cooling circuit. The freezer turns on. The keg of beer, being almost full, has considerable thermal mass, and could take quite some time to cool down below the STC-1000's threshold to cut the cooling. By then, the freezer itself could be well below freezing.

The near-empty keg has much less thermal mass, and would cool much more quickly than the full one. I'm concerned about the risk of the beer in the near-empty keg actually freezing solid before the full keg finally cools down enough to cause the cooling cycle to cease.

That's why I measure ambient temperature in my keezers.