Temperature Probe Placement

[copper2hopper]

Morning everyone!, Sorry to start a new thread on this topic but I didn't want to resurrect an old one from the ones I have extensively read through. From what I gathered is that people have their personal preferences on where they place their probe that is connected to the external thermostat ranging from dangling in the air in the chamber, in a thermowell, insulated to the side of the carboy...etc. I am anxiously awaiting for the arrival of my Johnson A419 controller next week to connect to my brand new 7 cubic foot Criterion chest freezer I just bought from Menards this week. Finally!.....fermentation temperature control!!!...super excited.

I think I have decided to go with the method of having the Johnson A419 probe stuck up against the exterior fermenter wall protected by some extra reflectix I have available. And then to have a separate digital thermometer probe monitoring the ambient chamber air so I know how hard or not hard the chest freezer is working to keep the ambient air at "xx" degrees while the Johnson A419 controller temperature prob is reading "xx" degrees. Obviously I'm trying to keep that Johnson A419 controller temperature prob to maintain a constant temperature at the recommended temperature for that particular style of beer paired with whatever particular type of yeast I'm using.

I guess my question is, through the other threads I have read, it seemed like a vast majority of people here have the probes switched the other way around and not the way I have listed above? It seemed backwards to me me and that's why I feel like doing it my way listed above would make more sense. Do any of you have it as I have listed above? Pros vs Cons??? etc... Looking for some guidance being that it will be my first time doing this. Thank you in advance

 

[SanPancho]

here's what i do- precise fermentation control.

buy a two-hole carboy cap. few bucks at brew shop.

then i bought this stainless steel tube on amazon- http://www.amazon.com/gp/product/B004XN9ZP6/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

then i cut it in half, and used a vice to crimp down the end so its sealed up tight. i also ground it a bit to soften edges, and polished it a bit, but probly not really necessary if you just clean and sanitize it well.

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the johnson controls probe slides right down the tube. presto! you just built a thermowell. and the tube is long enough (36") to make at least two thermowells at 18" each, or three one footers. not bad for 20 bucks.

the bummer is that the thermowell is too skinny to seal up the fat tube on the carboy cap by itself, so i just cut a bit of vinyl hose and slid it over the thermowell as a sleeve to get a night tight seal. you can just see a tiny bit of it coming out of the orange cap around the steel.

for the airlock i cut down the skinny orange tube a bit and shoved my airlock in to it. since this tube comes out of the cap at an angle, and the sanitizer weighs down the airlock, i used a rubber band to secure it to thermowell so it sits more vertically and not flopping to the side.

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now just decide if you want the probe sitting towards the bottom, middle or top of your carboy and you've got a precise temp reading of YOUR FERMENTING BEER. not ambient air, not plastic or glass carboy walls. the actual fermenting beer. now you can have precise fermentation control.

the last trick is to figure out how your keezer works and set it to not go wildly below the set point. one of mine constantly drops the temp down to 52 before letting back up to 55. not ideal. still trying to find sweet spot of the freezer settings. sometimes its a good idea to keep some other crap in your keezer just to provide thermal mass, which helps moderate those temp swings. spare fermenters or cornys with just regular water in them help alot. or your beer that's aging, or bottled already, etc.

two notes-
1- do not use the cut side of the tube to crimp down and put in beer. stainless will rust if it isnt allowed to passify. either leave it out for a week to develop its protective coating on its own, or read up on passivating stainless and do that.
2- this tube only fits my johnson controls probe. ive got a ranco brand temp controller and the probe is too fat to slide down easily. just get on amazon and find the next larger inside diameter sized tube if you have a ranco. if you have some other brand, measure as precisely as you can. maybe try a local welding shop if you dont want to chance it.

 

[solbes]

I think thermowell would be the most accurate. They sell carboy thermowells at Midwest Supplies and elsewhere:

http://www.midwestsupplies.com/stopper-thermowell.html

I use buckets for most of my primary fermentations, plus I'm cheap. So I just tape the A419 probe against the side of the fermenter and then insulate to reduce fridge temp effects. I believe this method to be accurate to within a degree (or possibly two) of a thermowell. I've tested it in the past by putting the same probe in the beer. You want to control the temp of beer, not the air. The beer temps can go quite a bit warmer during the really active phase, so having the probe in the air would not adjust for this.

Two pennies, cheers!

 

[copper2hopper]

Thanks fellas! Nice write up and informative post with links there SanPancho. Question about that thermowell method (or either method for that matter)... When you have the probe in place in the thermowell during that initial phase of fermentation where temps are naturally running higher in the fermenter, and you want to have that wort at a constant....say....68 degrees for example. Is that what you set your "set point" at on the thermostat with a temperature differential of 1 and then let the chest freezer do its magic?

 

[solbes]

I set my controller 1 degree higher than I want it to control to. I also set my A419 to the lowest differential, which I belive is 1 degree.

Example, I have my bock in my fridge lagering right now. In a perfect world, I would keep this baby cool as a cucumber sitting right at 33F. I set the controller to 34F. Thats when it turns the fridge on (34F). It runs for a minute or two and the temp drops from 34 to 33F. It continues to run the fridge until it holds at 32 for a little bit of time. Then it goes through the slow warming cycle from 32 up to 34F. So on average, the beer is at 34 for roughly 10% of the time, at 33 for 70% of the time, and at 32 for about 20 % of the time.

Note, I have a fridge which I think is designed to cycle more often than a freezer. I'm not sure if a 1 degree differential would be good for the compressor for keezers. Might want to double check with others that this won't reduce its operable life expectancy.

 

[copper2hopper]

Crap!!! I just read up on more in some threads about temperature swings AFTER I just purchased a stopper-thermowell from homebrewing.org. Sounds like without a heating element incorporated into the chamber, you get large temperature swings with the thermowell route. Should stuck with my gut on this one and saved $25 bucks and just gone with the probe insulated to the side of the carboy route like you solbes. Oh well....either way it will still be nice to have a reading of the internal temp.

Wow I didn't know bocks had to ferment that low, but yeah I would agree trying to keep it that low would put a lot of stress on the compressor for a freezer OR fridge. But I typically brew hoppy APA's and IPA's where fermentation stays higher in the 60's so hope I will be ok with my chest freezers compressor.

 

[solbes]

Crap!!! I just read up on more in some threads about temperature swings AFTER I just purchased a stopper-thermowell from homebrewing.org. Sounds like without a heating element incorporated into the chamber, you get large temperature swings with the thermowell route.

Interesting, can you elaborate? Trying to figure why you would get large temp swings, requiring a heating element. Whether the probe is in the beer (Twell) or stuck to the outside, I would think it would be very similar (within a degree or so).

 

[CGish]

I use a BrewPi rather than the Johnson controller so I don't know if this will help you, but here is how I set up the probes and blowoffs. The 12" thermowells came from Brewers Hardware.

Going clockwise starting with the carboy, there is a 5 gallon PET carboy, a five gallon bucket, and a 6.5 gallon bucket. The carboy is working as a secondary for an apricot addition to half of a Cream of Three Crops batch.

Crap!!! I just read up on more in some threads about temperature swings AFTER I just purchased a stopper-thermowell from homebrewing.org. Sounds like without a heating element incorporated into the chamber, you get large temperature swings with the thermowell route. Should stuck with my gut on this one and saved $25 bucks and just gone with the probe insulated to the side of the carboy route like you solbes. Oh well....either way it will still be nice to have a reading of the internal temp.

Wow I didn't know bocks had to ferment that low, but yeah I would agree trying to keep it that low would put a lot of stress on the compressor for a freezer OR fridge. But I typically brew hoppy APA's and IPA's where fermentation stays higher in the 60's so hope I will be ok with my chest freezers compressor.

Interesting, can you elaborate? Trying to figure why you would get large temp swings, requiring a heating element. Whether the probe is in the beer (Twell) or stuck to the outside, I would think it would be very similar (within a degree or so).

While your ambient temp will swing around a lot, a thermowell and a good control (the Johnson's reputation is excellent) should keep the beer temp within a tenth of a degree or so. To give you an example, here is the chart from my latest fermentation. The fermentation is the part in the black box. The two spikes - one up and one down - come from working with the probes. I had to reset the unit due to an electrical problem - that was the first low spike - the BrewPi read Celsius for a few minutes. The second high spike was due to taking the probe out and moving the fermenters around. The actual beer temp did not move.



This is the ambient refrigerator temps from the same time:



You can see that the ambient moves up and down in a range, but the beer never moves more than a tenth or two of a degree.

 

[copper2hopper]

Interesting, can you elaborate? Trying to figure why you would get large temp swings, requiring a heating element. Whether the probe is in the beer (Twell) or stuck to the outside, I would think it would be very similar (within a degree or so).

The information I am gathering is that with using a thermowell, you're measuring the center mass of the wort that is fermenting, so when trying to keep that fermenting wort at the peak of its fermentation when things are running their hottest at a particular temp (say 65 degrees for example), it seems like it will take a lot of work on the chest freezers part to cool that wort to its core down to 65 and keep it there and by doing so it will be pumping the ambient air inside the chest freezer down too low (say 45 degrees for example) and by the time that controller probe reads and tells the thermostat that it is ok to turn off the chest freezer compressor, the ambient temp is so low that it will swing that wort temp down too low below the target set point at which the thermostat is set to keep it at. A heating element I feel would eliminate that overshot temp swing on the cooling.

I feel like if the controller probe is stuck/insulated to the side of the fermenter, it's closer to the ambient air and you won't have a major low end temp overshoot.

 

[copper2hopper]

Holy COW CGish! Cool setup!! and thank you for your info!

 

[solbes]

When the beer is in the highly exothermic part of fermentation, cooling will be called upon frequently. It doesn't take very long at all before the temp recovers that bottom degree to the nominal temperature. Maybe 10-15 minutes and its already calling for cooling again. I don't think you will have problems with overshoot in this time period. I think you'll find that overshoot problems in general are non-existent with the setup you're getting. I know the A419 has the ability to heat as well (change a dip switch I think). I've never gotten that fancy with it, and don't plan to (50 batches or so using it).

I would suspect that the temperature of the wort from outside of the fermenter to the inside is within a degree. Maybe more variation from top to bottom. But the thermowell puts your probe about dead center, were you'd want to measure. I think it'll work out great!

 

[drgonzo2k2]

Good questions, and a lot of good info in this thread. I think the takeaway should be there are lots of different equipment and methods to achieve what you're trying to do, so you should pick whichever sounds best to you (and is within the budget you've allotted for this part of your setup), and then do some testing to get it dialed in before you use it to ferment beer the first time.

I have a Johnson A19 controller setup similar to the way SanPancho described, except I use that to regulate the temp in my full size freezerless fridge that I use to cellar commercial brew. Keeping my controller set at 54F keeps my beer at a near constant 53F. For this setup I just have the Johnson probe ran into an empty bomber of distilled water (the probe is waterproof) that sits on my middle shelf.

For all of my fermenters though I use the Speidel HDPE ones, and I've outfitted them with thermowells exactly as described in this post. The procedure is simple enough, and the cost of parts low enough, that I figured if I'm going through all the extra cost and effort to setup fermentation chambers, I might as well go the extra mile to be as accurate as possible. I have 3 Speidels setup this way.

Then I have two fermentation chambers. One is a repurposed large wine shelf which I've outfitted with 50W worth of reptile heat tape to handle the heating aspect, and the other is a small chest freezer that is outfitted with 150W of reptile heat tape. The first one is my "primary" chamber for things like IPAs and pale ales that are going to finish up quickly, and I use the second one for things that are going to take longer and/or need more heating/cooling (like lagering and saisons).

To control both setups I use STC-1000 boxes which I wired up myself. One is actually the InkBird model from Amazon (displays F instead of C only), but it's essentially identical. This is where the testing to get it dialed in is crucial... For my fridge setup, I have it set to whatever temp I want with a .5 degree differential, and it works perfectly. The freezer though I had to go with a 2 degree differential to get it dialed in and not have the heat/cool battling each other.

Also, if you are going to go with a thermowell, be sure to use some sort of thermal paste inside of it to get a good temp measurement with your probe. If you just stick it in there, it will not be quite as accurate (measuring air temp which is insulated from your wort temp by a layer of stainless steal) and at just a specific spot (as opposed to the paste being acted upon by the temp of the wort and that averaging out inside your thermowell). The cheapest thing I've found is diaper rash cream (yes I'm serious). Zinc Oxide in a petroleum jelly, which is perfectly fine for the temps we're talking about, as opposed to Zinc Oxide in a Silicone jelly which is what's used for high heat like CPU heat sinks, etc.

Good luck with your fermenting!

 

[copper2hopper]

Thanks solbes, yeah this thing has some confusing instructions. To add a heating element you have open it up and change pins around and stuff or something like that. Unless you're electrician this stuff is hard to understand. I posted in another thread about setting up this unit and maybe you can help me out too though....What "mode" is this thing defaulted at out of the box from the factory? Cooling/Cut-in mode, Cooling/cutout mode, Heating/Cut-in mode or Heating/Cutout mode. I feel like I'm going cross eyed stupid trying to understand the PDF instructions I found online here. I'm looking to just plug and play this thing but wanna make sure It's good to go out of the box when I get home today. Also what does the "offset" temp setting do?

 

[drgonzo2k2]

Thanks solbes, yeah this thing has some confusing instructions. To add a heating element you have open it up and change pins around and stuff or something like that. Unless you're electrician this stuff is hard to understand. I posted in another thread about setting up this unit and maybe you can help me out too though....What "mode" is this thing defaulted at out of the box from the factory? Cooling/Cut-in mode, Cooling/cutout mode, Heating/Cut-in mode or Heating/Cutout mode. I feel like I'm going cross eyed stupid trying to understand the PDF instructions I found online here. I'm looking to just plug and play this thing but wanna make sure It's good to go out of the box when I get home today. Also what does the "offset" temp setting do?

As far as I remember, the A19 was plug and play for cool only mode out of the box. I just programmed my set temp for the beer cellar, set a 1 degree differential, and it worked exactly as expected. If your temp is exceeded, the fridge will kick in to cool you back down to your set point.

I'm pretty sure the offset is to correct any differences between what your A19 detects as the temp and the actual temp. So if it's calibration gets a bit off you can correct it.

I've had mine running for years in the cooling mode with no issues at all.

FWIW - the A19 is not designed to control both a heating and cooling source at the same time. It's one or the other, and like you said, you have to open it up to switch the modes. It's much simpler to just get a dual-stage controller like an STC-1000 and "set it and forget it" if you need both heat and cool.

 

[solbes]

When I last looked at mine, I seem to remember it being either cool OR heat, as drgonzo indicated. So you won't have that ability. Unless they are now setup differently than they were a few years ago.

 

[copper2hopper]

View attachment ImageUploadedByHome Brew1425938556.102109.jpgView attachment ImageUploadedByHome Brew1425938569.108564.jpg

Well...I got her all set I think. Set point is at 65. Differential is at 1 and ASd is at 10. It's only 63 in my basement here which is what I got that white digital thermometer reading the inside temp of the freezer. The controller probe (reading only 62 right now) is bungied to the side of the fermenter with two sheets of reflectix pinning it in place for insulation. I also bought a small desk fan on the way home to stick in there to get good air circulation (which looks like is generating heat cuz now my ambient temp prob is reading 64 since I've been writing this post). Let's hope it works now!

 

[ScrewyBrewer]

I use the BrewsBySmith STC1000+ Fermentation Kit and program the hysteresis to 0.5 degree. I also use a thermowell inside my ale pail to measure the core temperature of the fermenting beer. During primary fermentation there's plenty of turbulence in the wort created by the yeast as they chew their way through all that sugar. Right now my fermentation chamber is in a 45F garage and fermenting Ales only requires providing heat as needed to maintain 66F.

With the set point at 66F once the wort reaches 65.4F the 32 watt Fermwrap laying under the fermentor switches, on providing a slow heat to the bottom of the fermenting beer. I've put another digital thermometer inside the fermentation chamber and witnessed the ambient air swing at least 5F higher than the set point before the beer reached 66F again. But even with that swing in ambient air temperature the beer never deviated more than +-0.5F from the set point.

 

[copper2hopper]

Wow that's a nice piece of equipment there man. I wish I woulda known it existed before I bought my Johnson A419. I mean I knew the STC existed but not like you have it all set up ready for plug and play eliminating all the DIY wiring I know nothing about. I woulda bought yours instead and incorporated a heating element in my set up

 

[drgonzo2k2]

That is a nice piece of kit. Of course now that I've assembled two on my own, I think that price is a little high, but it is nice to get everything in one box all ready to go. If you're considering building your own STC-1000, I highly encourage it. I was scared to death I was going to burn the house down with my first one, as I'd never done any sort of wiring, but an hour later it was all up and running. The second one took even less time since by that point I was an "expert."

 

[MisterGreen]

The information I am gathering is that with using a thermowell, you're measuring the center mass of the wort that is fermenting, so when trying to keep that fermenting wort at the peak of its fermentation when things are running their hottest at a particular temp (say 65 degrees for example), it seems like it will take a lot of work on the chest freezers part to cool that wort to its core down to 65 and keep it there and by doing so it will be pumping the ambient air inside the chest freezer down too low (say 45 degrees for example) and by the time that controller probe reads and tells the thermostat that it is ok to turn off the chest freezer compressor, the ambient temp is so low that it will swing that wort temp down too low below the target set point at which the thermostat is set to keep it at. A heating element I feel would eliminate that overshot temp swing on the cooling.

I feel like if the controller probe is stuck/insulated to the side of the fermenter, it's closer to the ambient air and you won't have a major low end temp overshoot.

For what it's worth, I use both a thermowell probe and a stick-on thermometer and they always read the same. A 5 gallon carboy just isn't a large enough volume of liquid to see a difference between core and perimeter.