Poll: Fermentation chamber temperature probe placement

I am in the process of making a converted chest freezer fermentation chamber in my garage picked up a $50 chest freezer yesterday:

and I have one of those ebay aquarium controllers on order and will be wiring it up to control the compressor, lightbulb and fan.
http://cgi.ebay.com/Mini-Digital-Te...tem&pt=LH_DefaultDomain_0&hash=item4150d3b29f

I have read tons of threads and opinions on this issue of where and how I should place the temp probe so I posted a poll to see who is doing what

Thanks for participating

I tried all four ways. It seems that the best temperature control/variance that I have achieved has been wrapped in a papertowel on the floor of the freezer. I too use a 15.0 CF freezer as a fermenter.

I have the controller probe hanging in the air and use a separate digital thermometer to monitor the fermenter temp. I attached the thermometer probe to the side of the fermenter and cover it with some bubble foil insulation (I use a bungee to hold it in place). I think this method provides a reasonable approximation of the wort temperature. The insulation isolates the thermometer probe from the air temp. I use an indoor/outdoor thermometer for this. Even the cheaper ones seem to be quite accurate. This method has been working out very well for me.

Inside.

My big pink foam box has a Ranco probe duct taped to the bottom of the far corner away from the fridge.

Since the Ranco temp scale is a little...crude, I use a thermometer in a glass of water in the middle of the box as my "official" temperature.

A thermowell is the most accurate liquid temp reading you could get, because the yeast during primary fermentation generates heat, so there will be a variable offset between the actual wort temp and a separate liquid container's temp depending on yeast activity, as well as the air. A separate liquid container is better than air, though. You wort could be at 72 and the air or other water container could be at 65. For a kegerator, a separate liquid container is ideal, because you would not want to bring a warm keg in and have the freezer freeze the other cold kegs trying to pull down the temp of the warm keg.

bendavanza said:

A thermowell is the most accurate liquid temp reading you could get, because the yeast during primary fermentation generates heat, so there will be a variable offset between the actual wort temp and a separate liquid container's temp depending on yeast activity, as well as the air. A separate liquid container is better than air, though. You wort could be at 72 and the air or other water container could be at 65. For a kegerator, a separate liquid container is ideal, because you would not want to bring a warm keg in and have the freezer freeze the other cold kegs trying to pull down the temp of the warm keg.

Click to expand...

With all due respect, I generally disagree with most of the above.

1. IMO, a controller probe placed in a thermowell in the fermenter will result in larger temperature swings than having the probe in the air and monitoring the fermenter with a separate thermometer. The freezer will overshoot and undershoot a lot.

2. A controller probe in a container of water will also increase the response time resulting in overshoot/undershoot. All this does is increase the differential which you can adjust on the controller itself, so no need for a water bottle.

3. Introducing a warm keg of beer to the freezer will not cause the freezer to run constantly trying to cool that single keg. The heat transfer rate from the keg is not that fast. This just does not happen. I did have some keg freezing problems before I installed a fan. This happened because the poured beer was often too warm, so I kept turning the temp down eventually causing ice to form which blocked the dip tube. That seemed strange, but I finally figured out that the beer warmed as it passed through the lines and taps even though the kegs were colder than they needed to be.

4. IMO, trying to monitor the fermenter temperature with the controller probe is not the way to go. It's much better to have a separate thermometer to monitor the fermenter temp.

5. Attaching a thermometer probe to the side of a fermenter and isolating it with some insulation works really well. The temperature holds very steady within one degree or so this way and I believe that it provides a reasonable approximation of the actual wort temperature inside the fermenter. Using a thermowell may be a slightly more accurate method, but not worth the hassle IMO.

This is JMO, nothing more, but it's based on several years of experience and experimentation if that counts for anything.

I don't have a thermowell for my FV's but I've taped and insulated the temp probe to the outside of the fermenter. I've noticed the temp in the FV moves at a much slower rate than the surrounding air temperature, the ambient temp will at times be in the mid 60's while the FV temp, measured at the insulated probe, is in the low 70's.

Conclusion....Regulating the ambient as a function of the FV temp is the only way to go. Temp probe attached to the FV and insulated or in a temp well in the wert controls the fermentation temperature more accurately. IMO

thanks for all the replies..

I am leaning towards leaving the one probe in the air and putting a separate cheap thermometer on the carboy wall with some insulation

now for the important question...whats the best source for a cheap thermometer with a probe that I can attach to my carboy?....on a major budget here

My Son of Fermentation Chiller has a 2" pink styrofoam top piece that I drew a circle on it a bit off-centered.

I cut out about 1/2" of foam and pushed my dial therm through. It is about 12" or so long so it reads the air above the primary.

I also built a top for it so it can double as a transportable bar. When I lift the top off I can read the temp on the dial therm without removing the foam.

I plan on making another top exactly the same as the one I have.

I plan on tiling this top and installing a tower in the other one...eventually. This way the SOF can do double duty...:rockin:

Catt22 said:

With all due respect, I generally disagree with most of the above.

1. IMO, a controller probe placed in a thermowell in the fermenter will result in larger temperature swings than having the probe in the air and monitoring the fermenter with a separate thermometer. The freezer will overshoot and undershoot a lot.

5. Attaching a thermometer probe to the side of a fermenter and isolating it with some insulation works really well. The temperature holds very steady within one degree or so this way and I believe that it provides a reasonable approximation of the actual wort temperature inside the fermenter. Using a thermowell may be a slightly more accurate method, but not worth the hassle IMO.

Click to expand...

Am I missing something here?

You stated in #1 that the freezer would overshoot and undershoot because of a thermowell in the fermenter, then you stated in #5 that it would be the most accurate but not worth the heassle.

What hassle are you speaking of? If you have a decent temp controller you can set the hysteresis avoiding a gross over or under shoot of your desired temperature.

I think a thermowell would definitely be most accurate way to control fermentation temperatures for a single fermenter, but if you have a fermentation chamber with more than one fermenter and different beer styles using different yeasts, then having the probe in a seperate container of water might be a better solution, while keeping your fermentation temp a few degrees cooler during the "active" fermentation period.

My .02.

Schnitzengiggle said:

Am I missing something here?

You stated in #1 that the freezer would overshoot and undershoot because of a thermowell in the fermenter, then you stated in #5 that it would be the most accurate but not worth the heassle.

What hassle are you speaking of? If you have a decent temp controller you can set the hysteresis avoiding a gross over or under shoot of your desired temperature.

I think a thermowell would definitely be most accurate way to control fermentation temperatures for a single fermenter, but if you have a fermentation chamber with more than one fermenter and different beer styles using different yeasts, then having the probe in a seperate container of water might be a better solution, while keeping your fermentation temp a few degrees cooler during the "active" fermentation period.

My .02.

Click to expand...

Yeah, you missed something. In #5 I was suggesting that a thermometer probe, not the controller probe, in the a thermowell might provide a slightly more accurate indication of the actual wort temperature.

The hassle I'm referring to is actually installing a thermowell in a fermenter. I prefer the simplicity of not having any unnecessary penetrations into the fermenter. A thermowell requires a penetration and one more piece of equipment that requires careful cleaning and sanitizing. Not worth the trouble IMO.

vincemash said:

thanks for all the replies..

I am leaning towards leaving the one probe in the air and putting a separate cheap thermometer on the carboy wall with some insulation

now for the important question...whats the best source for a cheap thermometer with a probe that I can attach to my carboy?....on a major budget here

Click to expand...

I have several fermentation chambers and several different digital thermometers that I use with them. You can find cheap indoor/outdoor digital thermometers just about anywhere. Target and Wally World have them as well as Lowes and HD. Radio Shack too. You can find them as low as $10 and they are surprisingly accurate. I have one that is wireless which is kind of nice as you don't have to deal with the probe lead as on the hard wired type. The only downside to the wireless unit is that the transmitter is rather bulky, but that hasn't proved to be a problem. Attaching the thermometer probe to the side or top of the fermenter and covering it with some insulation works very well. In theory, the heat radiated by the fermenter will be trapped by the insulation and very closely approximate the internal temperature of the fermenter. I think I first heard of this method from Jamil or someone on the Brewing Network. All I can say is that I'm very pleased with the way it works.

I recently built a Son Of Fermentation chamber that contains one 6 gal carboy and uses a Johnson Controller to regulate a 5" fan blowing cold air into the chamber from 2 gallon frozen jugs of ice. Since you can only control the air temperature in the chamber it makes perfect sense to place its probe somewhere in that chamber and not worry able the wort temperature within the carboy. I bought a cheap $7 digital thermometer with probe that is within 1 deg of the Johnson probe and duct taped it with a 1/2" piece of dense foam covering it to the side of the carboy. I have used this arrangement twice now and it works beautifully to keep the chamber at the set point temperature. The beginning readings are usually 1-2 deg higher on the carboy probe during initial ferment but near end of ferment the reading comes more in line with the Johnson probe temp.

jroot said:

Since you can only control the air temperature in the chamber it makes perfect sense to place its probe somewhere in that chamber and not worry able the wort temperature within the carboy.

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If you're not worried about the temperature within the carboy, why build a chamber in the first place?

hmmmm cheap

in for one!

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=290427576797&ssPageName=STRK:MEWNX:IT


I may be brave enough just to sanitize and dunk this right in the fermenter

Thermowell for me I like to know the exact temp of the fermenting wort.

Brew-boy said:

Thermowell for me I like to know the exact temp of the fermenting wort.

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+10 I can deal with the extra little hassle be it so little being a deep well in the fermenters lid aimed straight down into the heart of the fermenter. Come on how much more of a hassle is it to clean and sterilize? Accurate temps are my goal.

Catt22 said:

With all due respect, I generally disagree with most of the above.

1. IMO, a controller probe placed in a thermowell in the fermenter will result in larger temperature swings than having the probe in the air and monitoring the fermenter with a separate thermometer. The freezer will overshoot and undershoot a lot.

Click to expand...

With all due respect, only if you do it wrong. Use a properly tuned PID to take care of overshoot/inertia problems in your cooling loop.

RDWHAHB said:

With all due respect, only if you do it wrong. Use a properly tuned PID to take care of overshoot/inertia problems in your cooling loop.

Click to expand...

PID with refrigeration equipment is bad... Will kill the compressor in no time.

RDWHAHB said:

With all due respect, only if you do it wrong. Use a properly tuned PID to take care of overshoot/inertia problems in your cooling loop.

Click to expand...

Yes, obviously it would if one were using a PID controller. No one that I know uses a PID controller on their fermentation chamber fridges or freezers. Most home brewers I know use a Johnson, Ranco or Love non-PID type thermostats. IMO, a PID for this type of application would be major overkill. A simple totally dumb digital or analog switched thermostat works just fine for me.

jpc said:

PID with refrigeration equipment is bad... Will kill the compressor in no time.

Click to expand...

That's certainly good to know and now that you mention it, I can clearly see why.

Just add a delay cycle timer to save the compressor from short cycling.
I've used defrost time delays from Safeway store refrigeration systems that I worked on they're great. Being free also helps matters with the desire to test wild ideas.

BrewBeemer said:

Just add a delay cycle timer to save the compressor from short cycling.
I've used defrost time delays from Safeway store refrigeration systems that work great. Being free also helps with the desire to test these ideas.

Click to expand...

But would that not defeat the purpose of using a PID in the first place. The idea was to minimize the overshoot/undershoot with the PID. You toss a delay cycle into that mix and you would be back to a large temp swing. Perhaps I'm missing something though, as I have only a very rudimentary understanding of PID's and how they operate and it's likely to stay that way for at least a while longer.

The longer times between compressor cycles the more stable the temps in the fermenter's temp well i've found. Granted a wider temp swing within the keezer, who cares about air temp swings it's the fermenter's contents I want constant. I adjusted and tuned to the system at hand. This with a Johnson control kicking a relay for the compressor load. Granted a 30 year old POS keezer it still maintains a rather constant temp for fermenting is all I ask. No PID control here plus no short time internal keezer air temp swing worries.

1) PID doesn't kill cooling equipment, short cycly times do. Short cycles should be avoided with t-stats as well.
2) PID is not overkill if you are experincng wild over/undershoots with your temp control. A good PID can be had for the same $$ as a ranco/johnson.
3) you want to cntrl the fermentation temp, not the air temp. Measuring anything other thanthe fermenting beer's temp introduces error.

RDWHAHB said:

1) Measuring anything other thanthe fermenting beer's temp introduces error.

Click to expand...

I've had my share of errors on my own without adding ideas from others.

With due respect, I couldn't disagree with you more as to how to control fermentation temp. The ONLY thing you can directly control is the air temperature within the chamber. Keeping that as near to your set point temp is the only way to minimize the ferment temp swings which is the primary thing you want to avoid anyway. With the probe monitoring the fermenting wort the control will not kick on until there is a warming of the wort and then a big delay until it once again falls to the set point temp. However, with the control probe monitoring the chamber temperature the wort has a much greater chance to remain stable as the chamber quickly returns to set point temp.

In my experience controlling the ambient air will eventually get you to the correct temps but it can take a lot longer to do so. Thermowells in my set up work better and while I might overshoot slightly, this tends to dissipate as I get close to desired temps. I can't explain it in scientific terms, it just works for me. As to sanitizing the thermo, it takes a minute.

I've tried it all of those ways and having the controller probe touching the wall of the fermenter is the best compromise. It is affected by both the inside air as well as the fermenting wort. If it's in the center of wort in a thermowell, you'll undershoot the temp. The fridge will become a brick of ice before 5 gallons reacts. Putting the probe in a glass of water is the worst because it is as isolated from the wort temp as you can get. If the ferment is very active, it will be hotter than you want and take a long time for that heat to register in the satellite liquid.

jroot said:

With due respect, I couldn't disagree with you more as to how to control fermentation temp. The ONLY thing you can directly control is the air temperature within the chamber. Keeping that as near to your set point temp is the only way to minimize the ferment temp swings which is the primary thing you want to avoid anyway. With the probe monitoring the fermenting wort the control will not kick on until there is a warming of the wort and then a big delay until it once again falls to the set point temp. However, with the control probe monitoring the chamber temperature the wort has a much greater chance to remain stable as the chamber quickly returns to set point temp.

Click to expand...

+1 IMO, you have it right. This is also the reason I suggest attaching a separate thermometer probe to the side of the fermenter and insulating it from the chamber air. The controller probe in the air will register fairly wide temperature swings, but without the separate thermometer you can only guess at what the average fermenter temp might be. I can maintain a very steady fermenter temp using this method.

Catt22 said:

+1 IMO, you have it right. This is also the reason I suggest attaching a separate thermometer probe to the side of the fermenter and insulating it from the chamber air. The controller probe in the air will register fairly wide temperature swings, but without the separate thermometer you can only guess at what the average fermenter temp might be. I can maintain a very steady fermenter temp using this method.

Click to expand...

that is my plan....hang the probe for the controller in the air, and then attach a separate thermometer to the fermenter.....then I can check the fermenter temp daily and adjust accordingly

I have one in the beer and one in the air. The beer probe controls heat and the air probe controls cold. I set the heat to kick on 1 degree below desired ferment temp and set the cold to keep the ambient air temp a few degrees below desired ferment temp the first few days of fermentation to help push down temp during the high exothermic phase and then put at desired temp the rest of the time.

Bensiff said:

I have one in the beer and one in the air. The beer probe controls heat and the air probe controls cold. I set the heat to kick on 1 degree below desired ferment temp and set the cold to keep the ambient air temp a few degrees below desired ferment temp the first few days of fermentation to help push down temp during the high exothermic phase and then put at desired temp the rest of the time.

Click to expand...

That's the oddest method I've heard of so far, but I would bet there are some others out there somewhere that might top it. There just have to be.

RDWHAHB said:

1) PID doesn't kill cooling equipment, short cycly times do. Short cycles should be avoided with t-stats as well.
2) PID is not overkill if you are experincng wild over/undershoots with your temp control. A good PID can be had for the same $$ as a ranco/johnson.
3) you want to cntrl the fermentation temp, not the air temp. Measuring anything other thanthe fermenting beer's temp introduces error.

Click to expand...

Do you actually have fridges or freezers that you control with a PID or are you talking in theory only? You'll be the first that I've heard using a PID for this if you do. I'm kinda wondering why this is not more common if the costs are a push and the performance so much better.

Cat22:
Not mine, but:
info on PID - fridge - freezer.
https://www.homebrewtalk.com/f51/how-wire-auber-syl-2362a2-pid-fridge-157513/

bendavanza said:

Cat22:
Not mine, but:
info on PID - fridge - freezer.
https://www.homebrewtalk.com/f51/how-wire-auber-syl-2362a2-pid-fridge-157513/

Click to expand...

Yeah, I now I do remember that thread. Taking another look at it I notice that basically the Auber PID parameters were selected to make it operate essentially just like the digital Johnson's, Ranco & Love's. IOW, there's not much in the way of Integration or Differentiation going on if you keep those in the null mode. That would be the "I" & the "D" part of PID IIRC. Looks to me like only a setpoint, a temperature differential and an anti-short cycle delay were used and nothing else. I can do all of that with my digital Johnson and it's plug and play. Perhaps I'm missing something.

Bobby_M said:

I've tried it all of those ways and having the controller probe touching the wall of the fermenter is the best compromise. It is affected by both the inside air as well as the fermenting wort. If it's in the center of wort in a thermowell, you'll undershoot the temp. The fridge will become a brick of ice before 5 gallons reacts. Putting the probe in a glass of water is the worst because it is as isolated from the wort temp as you can get. If the ferment is very active, it will be hotter than you want and take a long time for that heat to register in the satellite liquid.

Click to expand...

Bobby

So with your method you just have the probe touching the fermenter wall but do not insulate it from the surrounding air?

I've tried about every method mentioned and finally settled on what I think is the ideal configuration:

1. Installed a muffin fan to circulate the air in all of my freezers and fridges. I run the fans continuously.

2. Controller probe placed so that it is in the air or attached to the side of the fridge if the cooling coils are not in the walls. IOW, not in contact with cooling surface.

3. I use a separate digital indoor/outdoor type thermometer to monitor the fermenter temps with the probe attached to the side of the fermenter and covered with a small piece of insulation. This traps the heat radiating from the fermenter and approximates the internal temperature while isolating the probe from the air temperature in the chamber. The single exception is my serving keggerator where I have the controller probe mounted directly in the air stream of the fan. I adjust the controller based on the temp of the poured beer out of the taps. No need for the separate thermometer in this case. I can't directly sample the beer in the fermenters, but I can do so out of the taps.

4. The analog Johnson controllers have a preset differential which IIRC is about 3 degress F and that works just fine. I set the digital one to a 5F differential and that also works just fine.

5. The fermenter temps are very stable with this method usually varying less than one degree F. I have found it necessary to dial the controllers down well below target temps during the first few days of fermentation when the high activity is generating a lot of heat. I then raise the temperature over several days once the activity slows. I have found that it is best to cool the wort well prior to pitching as once the high activity begins it is much more difficult to bring the temperature down.

I'm getting excellent results with this configuration. I have no controller probes in a containers of water. I have no controller probes inside the fermeter (with or without a thermowell). I've come to the conclusion that using the controller probe to regulate the air temp and also to monitor the fermenter temp is not the best way to do it, but according to Bobby, he is having success doing it that way so you might want to give it a try.

Sorry I wasn't clear, the probe goes against the side of the fermenter and is held there with a bungie cord. I slip a 3" x 3" piece of reflectix between the cord and probe as primitive insulation. I suppose you could use a piece of bubble wrap or even a kitchen sponge.

The main purpose for me is to make sure the probe senses any heat coming from an aggressive fermentation but also have it react quickly. A deep thermowell would account for the first goal but not the second. An alternative is to have a thermowell in the wort but very close to the outside wall. Same effect.

Once the ferment subsides, this is less important. Dangling in the open air would be fine for that as long as you don't open the door many times a day.