Author Topic: Fermentation Fridge - Thermocouple Placement?  (Read 16855 times)

Offline philm63

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Fermentation Fridge - Thermocouple Placement?
« on: July 22, 2012, 10:51:43 AM »
Just put a batch of APA in the primary this weekend and dropped it into my new chest freezer complete with a Johnson Control. My issue is the thermocouple does not stick to the side of the glass carboy - I used good quality duct tape - it just falls right off! I thought I cleaned the surface fairly well.

So I dropped a second carboy in there and wedged a piece of cardboard between them effectively holding the thermocouple against the primary - isolating it from the second carboy by the piece of cardboard. Crude, yes, but it seems to be working fine. For now.

My question is this; does anyone have a better method of fixing the thermocouple to the side of a glass carboy in such a manner that it will stay there on its own with good pressure against the glass for accuracy?

And are there "best locations" for a thermocouple in the fermentation fridge? I currently have it on the outside of the carboy centered top to bottom.
On Tap: Oatmeal Stout, IPA
Fermenting: Air
On Deck: Kolsch

Offline zymurgist05

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #1 on: July 22, 2012, 01:25:02 PM »
Try some aluminum tape...  worked really well for me.  It's a little expensive for this application, but this tape comes in handy for other jobs around the house. 

Offline abarnard

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #2 on: July 22, 2012, 02:04:34 PM »
Wouldnt worry too much about it.  As long as the ambient temp in the  cooler is at least 2-3 degrees lower than target fermentation temp you should be ok.
On tap: raspberry shandy, southern rye
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Offline philm63

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #3 on: July 22, 2012, 02:56:10 PM »
Thanks for the info, always appreciated.

Perhaps I'm looking too far into this; but being an engineer who does product safety testing for a living (including commercial refrigerators for food safety), I tend to dig deep.

Understanding the variability of the internal temperatures in a chest freezer regarding both vertical and horizontal gradients, and having only one thermocouple from which the controller gets its info, if I were to hang it in there just about anywhere (I tried this when I first got it) I'd be reading the air temperature in only one area under a no-load condition meaning it would fluctuate wildly as the thermocouple by itself does not represent a significant thermal mass. If I added a brass slug to the thermocouple it would stabilize things a bit, and while the gradients could still an issue, proper positioning of the slug could reduce this effect also.

Knowing this; my theory was that if I attached the thermocouple directly to the carboy, seeing how it represents a significant thermal mass compared to the total internal volume (7 cubic feet), it would act as a good steady load from which to regulate the temperature. Besides; the carboy and its contents are the very thing whose temperature we're trying to control as best as possible, no?

Feel free to smack me if I'm digging too deep.

On Tap: Oatmeal Stout, IPA
Fermenting: Air
On Deck: Kolsch

Offline bucknut

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #4 on: July 22, 2012, 03:39:40 PM »
I use a small piece of bubble wrap and paper towel to cover the probe, then cover it with mailing tape.    then I just set it at 1 or 2 degrees cooler than my desire ferm temp. There's a good article in the latest Brew your own mag that goes into great detail on this subject.

Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #5 on: July 22, 2012, 04:02:19 PM »
Wouldnt worry too much about it.  As long as the ambient temp in the  cooler is at least 2-3 degrees lower than target fermentation temp you should be ok.

I do not agree with this statement at all.  A typical profile looks like this:

Day0:  beer = ambient
Day1:  beer = ambient + 3
Day2:  beer = ambient + 5
Day3:  beer = ambient + 7
Day4:  beer = ambient + 5
Day5:  beer = ambient + 3
.....

For some beers (hefe's, and big beers over 70 pts) I see up to 12F difference between ambient and the beer temp. 

I use blue masking tape or metalic aluminum tape.  Don't forget to put a 1/2" layer of insulation on top of the temp probe after you tape it down.  I use double layers of carpet pad, or a cut up camping pad.  In this configuration your probe will read within 1/2 degF of the internal beer temperature.

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R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

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Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #6 on: July 22, 2012, 04:07:02 PM »
Thanks for the info, always appreciated.

Perhaps I'm looking too far into this; but being an engineer who does product safety testing for a living (including commercial refrigerators for food safety), I tend to dig deep.

Understanding the variability of the internal temperatures in a chest freezer regarding both vertical and horizontal gradients, and having only one thermocouple from which the controller gets its info, if I were to hang it in there just about anywhere (I tried this when I first got it) I'd be reading the air temperature in only one area under a no-load condition meaning it would fluctuate wildly as the thermocouple by itself does not represent a significant thermal mass. If I added a brass slug to the thermocouple it would stabilize things a bit, and while the gradients could still an issue, proper positioning of the slug could reduce this effect also.

Knowing this; my theory was that if I attached the thermocouple directly to the carboy, seeing how it represents a significant thermal mass compared to the total internal volume (7 cubic feet), it would act as a good steady load from which to regulate the temperature. Besides; the carboy and its contents are the very thing whose temperature we're trying to control as best as possible, no?

Feel free to smack me if I'm digging too deep.

You've got the right idea, Phil.  If you want to control the beer temp, you need to measure the beer temp.  The activity of fermentation generates quite a bit of heat.  So, your controller will have to work hard before fermentation starts, and after fermentation finishes....but, in the middle the yeast will do a lot of the work themselves.

In the future, you will want to get more controllers.  One for the air temp inside your fridge, and one for each beer.  I use heating pads to heat each carboy or bucket while keeping the air temp down at 45F or so.  I can ferment several different beers at several different temperatures this way...
R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

Offline philm63

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #7 on: July 22, 2012, 06:05:40 PM »
Thanks, Tom. All good Stuff.  I know based on good ol' physics the fermentation, if very active, will generate heat so controlling that in the first few days is crucial to reducing potential negative effects from higher temperatures such as fusel alcohols.

Your methods look like they'll fit the bill nicely, thanks again.

On Tap: Oatmeal Stout, IPA
Fermenting: Air
On Deck: Kolsch

Offline abarnard

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #8 on: July 23, 2012, 09:30:23 AM »
Wouldnt worry too much about it.  As long as the ambient temp in the  cooler is at least 2-3 degrees lower than target fermentation temp you should be ok.

I do not agree with this statement at all.  A typical profile looks like this:

Day0:  beer = ambient
Day1:  beer = ambient + 3
Day2:  beer = ambient + 5
Day3:  beer = ambient + 7
Day4:  beer = ambient + 5
Day5:  beer = ambient + 3
.....

For some beers (hefe's, and big beers over 70 pts) I see up to 12F difference between ambient and the beer temp. 

I use blue masking tape or metalic aluminum tape.  Don't forget to put a 1/2" layer of insulation on top of the temp probe after you tape it down.  I use double layers of carpet pad, or a cut up camping pad.  In this configuration your probe will read within 1/2 degF of the internal beer temperature.

(also engineer)

Tom,  thanks for the info.  My experience with refrigeration comes from 20 yrs in foodservice.  Set the walkin cooler around 38 for internal food temp of 40.  With the ongoing reaction of the yeast it makes sense  the beer temp will vary over time.  Does air movement effect your above figures?  Food cools faster when forced air is used so would the addition of a fan in the ferm chamber help to remove more heat from the fermentor reducing how hard the controller works? 
On tap: raspberry shandy, southern rye
Up next: blonde ale

Offline Wingeezer

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #9 on: July 23, 2012, 10:20:51 AM »
I too was having problems with taping the sensor to a carboy and found it a nuisance. 

What I do now is to use an adjustable flat bungee cord wrapped around the carboy.  I put a couple of small squares for dense foam material over the sensor, also strapped under the bungee.

Works fine and takes seconds to put on and off.   

I also use a brewhauler and  a simple 2x4 rolling gantry crane with a boat winch and pulley arrangement to handle kegs carboys in and out of the chest freezer to avoid accidents as I have back problems.  That works great too!


Brian

Offline jomebrew

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #10 on: July 23, 2012, 11:55:27 AM »
I use blue painters tape.   I have some blue tape around the edges of some thermal bubble wrap (from home depot) I dry the carboy, place the thermocouple between the insulation and the carboy and quickly rub the edges of the tape to the carboy.

I do it this way with glass and plastic carboys (I only use plastic now).  It always sticks and stays. 

I have a 6" computer fan on a 12V wall wart circulating air.  This helps wick away heat generates by the fermentation. 

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #11 on: July 23, 2012, 05:11:25 PM »
I use the painters tape too, and use a piece of styrene with a valley notched in it to hold the sensor for 5 gallon batches.  The painter tape doesnt leave glue residue on your carboy.   For 10 g I use a skinny hollow styrene rectangle, insert the sensor in the hollow space.  The rectangle is open on the 2 sides facing the carboys and I wedge it between the 2 carboys.

Offline philm63

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #12 on: July 23, 2012, 05:23:47 PM »
Got plenty of painter's tape in the basement, probably even a bungee cord or two, and I'm sure I could dig up some dense insulation material somewhere - plenty of viable options - thanks for the tips!

A small fan, eh? Seems to me circulating the air should negate the gradient issue altogether helping to stabilize temperatures in the carboy much faster. And wouldn't circulating air also reduce humidity? I'm thinking mold here. I can see condensation on the walls inside the freezer, and if left unchecked at temperatures in the mid-to-high 60's, we'd have mold for sure. Any ideas on this one?
On Tap: Oatmeal Stout, IPA
Fermenting: Air
On Deck: Kolsch

Offline tom_hampton

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #13 on: July 23, 2012, 06:34:48 PM »
Tom,  thanks for the info.  My experience with refrigeration comes from 20 yrs in foodservice.  Set the walkin cooler around 38 for internal food temp of 40.  With the ongoing reaction of the yeast it makes sense  the beer temp will vary over time.  Does air movement effect your above figures?  Food cools faster when forced air is used so would the addition of a fan in the ferm chamber help to remove more heat from the fermentor reducing how hard the controller works?

Absolutely, a fan will increase the rate of heat uptake by the surrounding air.  It will also improve the rate of heat exchange with the walls of the freezer.  Its a relatively linear function of air flow rate. 

 
A small fan, eh? Seems to me circulating the air should negate the gradient issue altogether helping to stabilize temperatures in the carboy much faster. And wouldn't circulating air also reduce humidity? I'm thinking mold here. I can see condensation on the walls inside the freezer, and if left unchecked at temperatures in the mid-to-high 60's, we'd have mold for sure. Any ideas on this one?

Air circulation won't do much (if anything) for humidity.   The air relative humidity will stabilize at near 100%.  As the fermentation progresses some water will volatilize off with the CO2, which will put more water into the atmosphere.  Unless the water laden air has someway to escape that extra water is going to condense onto the colder walls of the cooler.  If the air were to dry out (in some unknown way) the condensation would re-evaporate and work to keep the RH near 100%.  So, if your walls are wet, your RH is going to be very high. 

I've heard of some people using damp-rid to absorb excess water....but, I can't attest to its effectiveness....and I have my doubts.  Without a RH meter, and some controlled experiments...its hard to know for sure.

I have an AC unit in my walk-in which works as a dehumidifier.  The condensation on the coils is drained out to the evaporator side and blows out with the hot exhaust.   So, this isn't a problem I've had to solve. 

R.I.P.:Belgian Blonde
On Tap: Apfelwein, Kolsch(v2), Pumpkin Ale, Belgian Specialty 
Aging/Storing: Coffee Porter, Chocolate Porter, Flanders Red, English Barlywine
Fermenting: Maggie's Altbier
Next Up: PtE(1.1), Belgian Dubbel?

Working thru all BCS recipes

KernelCrush

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Re: Fermentation Fridge - Thermocouple Placement?
« Reply #14 on: November 15, 2012, 05:11:34 PM »
Somebody tipped me off to plumbers putty.  Makes your probe stick to a sweaty carboy instantly, insulates at the same time, is re-useable, and its cheap to boot.