Fermentation control vs. actual fermentation temperature

[FirstAidBrewing]

Hey all,

So I am new to fermentation control and posting this to get some feedback and thoughts.

I am currently fermenting my first temperature controlled batch using a Johnson controller. Based on reading books and reading the forum, the general consensus is that internal fermentation temperatures can potentially (operative word I think) get 10 degrees hotter than the ambient temperature.

So I wanted to ferment at 62 (US-05 by the way) and thus set my controller to 52. And perhaps it's because I'm new to this, but I can't shake the feeling that it's a little on the low side.

What are your experiences like? Does the beer temperature rise ten degrees consistently per batch? Does it depend on the yeast strain? Or is the fact that I'm at least controlling temps make it a wash?

 

[sandyeggoxj]

A lot of people successfully tape their temperature probe to the outside of the fermenter (carboy, bucket, better bottle, etc) and then insulate it from the air so that it reflects the liquid temperature. Then you set the controller for the temperature that you want to ferment at. The air temperatures will swing very high and very low but the liquid wills stay steady. When I used carboys I always used a thermowell and inserted the probe into the thermowell. That worked well for me. I have heard it said that the difference between the center and the outside of the fermenter is less than .5ºF different.

 

[Dlou84]

I was just about to post a similar thread. I use the same controller in a freezer. I put the thermometer in a glass of water or the blow off jar. I actually started fermenting an IPA with US 05 Monday. I set my control to 61. On other batches I have set it at 65 or so. I am no pro but I think you will want to raise your temp some. I'm sure more experienced brewers will chime in.

I am also curious about something else. When I set my temp to 61 the freezer kicks on at 62. Once it realizes the temp has gone down the freezer can be as low as 57 10 minutes later. Does anyone know how to keep this from happening?

 

[danimalt]

A lot of people successfully tape their temperature probe to the outside of the fermenter (carboy, bucket, better bottle, etc) and then insulate it from the air so that it reflects the liquid temperature. Then you set the controller for the temperature that you want to ferment at. The air temperatures will swing very high and very low but the liquid wills stay steady. When I used carboys I always used a thermowell and inserted the probe into the thermowell. That worked well for me. I have heard it said that the difference between the center and the outside of the fermenter is less than .5ºF different.

i too use a thermowell and cant understand why people dont do the same. if you are going to do ferm temp control go all the way, its hardly more work than taping and covering to the outside.

 

[Dlou84]

Sounds like I should just get a thermowell too.

 

[JustLooking]

i too use a thermowell and cant understand why people dont do the same. if you are going to do ferm temp control go all the way, its hardly more work than taping and covering to the outside.

Because with a freezer fermentation chamber, during the peak of fermentation it will cause wort temperature fluctuations when the ambient temperature in the freezer goes subzero and the fermenter temperature continues to drop before thermowell can react. Less so with a refrigerator, but still.

 

[naturebrew]

i too use a thermowell and cant understand why people dont do the same. if you are going to do ferm temp control go all the way, its hardly more work than taping and covering to the outside.

How is taping a temp probe to a ferm vessel work? Takes a millisecond, costs nada, easy peasy.

 

[danimalt]

How is taping a temp probe to a ferm vessel work? Takes a millisecond, costs nada, easy peasy.

did i say it was work (rhetorical)? its my opinion ( and we both are entitled to ours) if u have the money to do ferm temp control the few extra bucks for a thermowell is worth it.

 

[danimalt]

Because with a freezer fermentation chamber, during the peak of fermentation it will cause wort temperature fluctuations when the ambient temperature in the freezer goes subzero and the fermenter temperature continues to drop before thermowell can react. Less so with a refrigerator, but still.

my temp probe goes into the thetmowell and when the temp of the wort reaches the set temp the relay on the controller opens.

 

[FirstAidBrewing]

My probe is under bubble wrap and taped to the side of my plastic fermenter. I guess I just envision the perimeter of my beer fermenting at 52-55, while maybe the dead center *might* ferment at 62. So if i read what y'all are saying correctly, my controller should be set higher than the 52 it is at?

 

[wardens355]

My probe is under bubble wrap and taped to the side of my plastic fermenter. I guess I just envision the perimeter of my beer fermenting at 52-55, while maybe the dead center *might* ferment at 62. So if i read what y'all are saying correctly, my controller should be set higher than the 52 it is at?

I would recommend setting at your desired ferm temp, or at most 1-2F below. I do not think there is any way you will have temperature differentials of more than a degree throughout the carboy. You are essentially making your ferm temp in the mid 50s.

I was just about to post a similar thread. I use the same controller in a freezer. I put the thermometer in a glass of water or the blow off jar.

I recommend taping to the carboy rather than using a glass of water. The temperature of the glass of water will not reflect the wort during vigorous fermentation and you will actually have a much higher fermentation temperature than you think you have. Also, think about this. A glass of water has a very small heat mass, so to change the temperature of a pint of water 1 degree, you need very little energy. For that 1 degree difference, you will probably only drop the temp of 5 gallons of wort less than 0.1 degree.

 

[zacster]

I'm using twin 3 gallon Better Bottles (they come packed that way in the carton too), and I place the probe in the indentations in the middle and push both bottles together. They fit nice and square together and the indentations provide an air pocket that would be the same as the fermentation temps around it.

As a test of whether you are being effective in your probe placement, just open the fridge/freezer. If your controller doesn't show a rising temp, you're good. With my setup above I can keep it open a long time before the controller ever moves. So whether you are using a taped on probe, a thermowell, or something else it really doesn't matter as long as you are measuring the ferm temp, not the air temp.

And surely (don't call me Shirley) you have a stick-on thermometer too to check?

In any case, even if you have the probe freely floating in the air, the warmer fermentation will heat the air around it, and the probe will sense it. The issue of a warmer fermentation vessel is more applicable in open environments where the surrounding air will absorb the extra heat and not compensate.

 

[JustLooking]

my temp probe goes into the thetmowell and when the temp of the wort reaches the set temp the relay on the controller opens.

And since the ambient temperature in the freezer is zero, the temperature of your fermenting wort continues to drop for a while. After this point the beer holds its temperature for some time while the ambient goes well above your set temperature. The beer temperature goes up and finally reaches the set for the compressor to kick in, but it continues to go up because the internal temperature in the freezer was allowed to get too high and takes time to cool again. By the time the beer reaches the set temperature the freezer is zero again. And the cycle repeats. As long as the yeast are producing heat stable equilibrium will never be reached. To prevent the yo-yo effect you have to control the ambient temperature, not just the wort temperature.

 

[02fx4dude]

I use a small chest freezer with temp controller to control ferment temperature. It has three sensors, one thermowell, one taped to the outside of the carboy, and one measuring air temperature. In my experience using the carboy mounted sensor for control results in the most stable temperature, and even during very active ferment the thermowell temperature is usually 0.5F to 1.0F above the setpoint and very stable.

However, IMO, how well this works depends on your particular setup. My freezer has the evaporator on the bottom, and the carboy sits directly on the bottom, thus transferring heat directly from the bottom of the carboy. The result is air temperature has little to do with carboy temperature and typically during fermentation is 0-10 degrees cooler than carboy temp.

If your setup is such that heat transfer is through the air inside your ferment chamber it will be different, most likely the air will become considerably colder to cool the carboy to the required temperature.

 

[sandyeggoxj]

And since the ambient temperature in the freezer is zero, the temperature of your fermenting wort continues to drop for a while. After this point the beer holds its temperature for some time while the ambient goes well above your set temperature. The beer temperature goes up and finally reaches the set for the compressor to kick in, but it continues to go up because the internal temperature in the freezer was allowed to get too high and takes time to cool again. By the time the beer reaches the set temperature the freezer is zero again. And the cycle repeats. As long as the yeast are producing heat stable equilibrium will never be reached. To prevent the yo-yo effect you have to control the ambient temperature, not just the wort temperature.

According to what you preach we should have wild swings in wort temperature. Reading your post it sounds like you read about this on the internet. As someone who has personally used this method I can tell you it isn't the end of the world that you preach. There is little thermal mass in the subzero temperature range. There is a lot of thermal mass, aka wort or beer, at a very stable temperature. I used a love controller and I had it set to 1 degree of swing. So a fermenter set at 67 would turn on the cooling at 68 and turn off at 66. That was the tightest it would go. It never varied from that range. The beer was stable and it turned out good.

Now.I have a glycol system with a black box controlling my fermenter. That has the swing set to .5°f so it Is a tighter dead band. If I were to follow your logic I should raise my glycol from 25 to 65 degrees so that it is closer to my fermentation set point. I wouldn't want a large temperature swing to change the beer temp quickly in case the yeast generated too much heat.

 

[phyllobeddo]

FWIW.... my fermentation chamber is a wine fridge that can hold two 3 gallon Better Bottles side by side (tightly). I built an STC 1000 to control temperature and I tape the probe to whichever Better Bottle has the latest batch in it. I have fermented four batches using the STC 1000 so far and what I have observed is that the fermometer on the side of the bottle and the STC 1000 probe reading stay within a degree or two of each other.

 

[lhommedieu]

I do something very similar. My carboys stay in an old fridge in my garage with an ST-1000 controller. I put the probe in a 1 gallon jug of water because I never seem to be able to get the tape/probe/bubble wrap to stay on the side of the carboy.

Since I'm brewing lagers these days the maximum manual temperature setting on my fridge is pretty close what I need for fermentation. I set the controller to 45F and check to see what's happening in the fermenters. If nothing is going on I'll bump up the setting a degree or two at a time until the yeast kicks in. I use a ceramic pet heat bulb for heating the inside of the fridge.

Starting next year I'm switching to conical fermenters and plan to insulate my garage so that I can use a infrared cube heater to bring the garage to the correct temperature. It's basically the same idea, but uses a bigger "box," and is actually a bit leaner than the system that I'm using now. This will mean brewing in the cooler months, but I like the idea of a more traditional schedule for brewing German lagers.

 

[naturebrew]

did i say it was work (rhetorical)? its my opinion ( and we both are entitled to ours) if u have the money to do ferm temp control the few extra bucks for a thermowell is worth it.

Like you said, your opinion, in mine, not required, why? Lots of reasons but mainly because I have flexibility in where I place the temp probe, with 3 sankes on the brew bench, this can become important.

 

[zacster]

FWIW.... my fermentation chamber is a wine fridge that can hold two 3 gallon Better Bottles side by side (tightly). I built an STC 1000 to control temperature and I tape the probe to whichever Better Bottle has the latest batch in it. I have fermented four batches using the STC 1000 so far and what I have observed is that the fermometer on the side of the bottle and the STC 1000 probe reading stay within a degree or two of each other.

If you put the probe in the space between the bottles you'll be reading the internal temp, especially since you have them tightly against each other. This is assuming you are using both to ferment at the same time, with the same batch.