Temperature Probe Position - Glass Carboys and Cornys

[RussPDX]

Good morning all -

I have been reading the threads on temp probe positioning in both fermentation chambers and keezers. In my keezer I currently just have my temp probe (Ranco) hanging in air. I had originally thought that I would put it in a thermowell and put that in a small jug of water but never got around to it. I cycle a bit more than I would like to so it is time to make a modification. I have read lots of threads where people insulate and tape the probe to the side of their vessels.

How would this work with metal corny's in a keezer? Would the metal have the appropriate temperature as compared to the interior fluid? I would think the liquid needs to at least be above the level of the probe.

Same question for glass carboys in a ferm chamber (about to build with an STC-controller). I know the best would be a thermowell, but I have seen lots of people talk about this method on plastic fermenters, wondering about glass.

If so, here is my thought. All comments appreciated and I will follow up with pics if I go this route.

As I have a pretty decent rate of keg turnover (code for I drink too much, but hey, it's a great excuse to brew more) so I would hate to keep having to tape things to the kegs, plus with 6 kegs in my keezer there is not much room so I am concerned about the tape getting knocked loose. My thought it to take a small plastic bottle and put a dowel or something in it to create a small void in the center. Put a slit in the bottle and thread a piece of elastic through the slit. Then fill the bottle with spray foam and let harden. cut the bottle in half vertically and trim the foam to create a nice mound of foam with a void for the probe and a built in elastic band. Add a little velcro to the elastic and then I can just strap my insulated, banded probe holder and probe to the side of a keg and it is a fast change when that keg gets low or I change over, I am assuming that I need the liquid volume above the level of the probe for accuracy so with this mechanism I could slide the probe down without having to deal with bubble wrap or tape.

Thanks for the impending advice.

 

[Stealthcruiser]

Sounds like it will work to me.
Then, when you change out a "blown" keg, do you strap the probe to the new keg, ( cycle times up again for a while), or strap to a known chilled one, and let the new one "come around" at it's own pace?

I like the thinking on the "strap on" (heh-heh...) probe mount, so that it does not get dislodged.

 

[RussPDX]

It would be a rare occurrence that I would have a single keg in there, so there would always be an acclimated keg to move the "strap-on" to.

 

[day_trippr]

A few years ago I stumbled across some 2" wide x 24" long adjustable velcro straps and the light bulb immediately went off. Pulled out the cell phone calculator, figured out what the circumferences of a corny keg and a 6.5g Italian carboy were, and bought enough straps for two of each (which was 6 straps).

I use a single strap on cornies to pin temperature probes against kegs with a chunk of inch thick closed cell foam for my carb/cold-holding fridge and my keezer, and daisy-chain two straps to do the same on carboys in the ferm fridge. In my 7 keg/six tap keezer I almost always have a full keg on stand-by (gives me one more slot in my carb fridge) so I use that one for running the controller. When that keg is put on tap it only takes a minute to move the thermostat to the next stand-by keg.

Kind of a fluke, but I had a picture of both vessel types with pads at the ready.

I keep my cold-carb fridge at the same beer temp as the keezer, so moving the probe is generally non-disruptive. If there was a larger differential I'd leave the probe on the "just tapped" keg and let the newcomer chill down...

Cheers!

 

[doug293cz]

Controlling a keggerator or kezzer is simpler than controlling a fermentation chamber. Fermentation is an exothermic (generates heat) process, so the liquid will be warmer than the ambient. Kegs with finished beer don't generate any heat, so they will eventually reach ambient temperature after a sufficient amount of time. Thus for kegs, you only need to control the ambient temp. In addition, a bunch of kegs has a significant thermal mass, and their internal temperature will vary much less than the ambient they are sitting in, if the ambient is cycling. If you have a controller with a 2 deg F hysteresis (dead) band controlling the ambient temp, then the keg contents will have a less than 2 deg temp range. The keg contents temp will always be less than the cooling on temp, and greater than the cooling off temp (cooling on temp is greater than the cooling off temp). If you look at some of the graphs in the brewpi threads, you can see how little liquid temp varies compared to ambient temp.

Just adjust your controller not to cycle too frequently, and everything should be fine with the temp sensor hanging in the ambient. RDWHAHB

Brew on

 

[RussPDX]

@day_trippr -that's just about what I was thinking....just seems so much easier. I guess it is working well for you with the glass as well? What are you setting your controller to if you say want to ferment at 50 def F?


@doug293cz - the Ranco single stage that I use for my keeper I do not believe has a setting to delay restarting the compressor and I hate to toss it just to replace wi an stc for that one feature.

I realize that fermenting bear exotherms, but unless I want to have a separate chamber for each carboy that is fermenting I am going to have to make some compromises. If I have a single batch in the chamber then I would set the temp to the actual fermentation temp and attach the probe to the outside as described. If I have multiple batches then I would attach the probe to the oldest batch and set the controller about a degree below my target.

If you have a different regimens, would love to hear it. I know others just measure the ambient and then set 6 degrees or so F below.


Sent from my iPad using Home Brew

 

[day_trippr]

[...]Just adjust your controller not to cycle too frequently, and everything should be fine with the temp sensor hanging in the ambient.

Even a factory thermostat doesn't try to deal with zero thermal mass. Check where they stick the bulb.

In my experience, the only way you'll avoid short-cycling a keezer with a "hanging probe" is to set your deadband a lot higher than some folks would desire.

By coupling the thermostat to that huge thermal mass in the keg you can set a tight differential/deadband and still go a long way between cycles. Right now with the ambient close to 80°F my keezer is cycling at just over 3:45 - with a 1.5°F differential...

Cheers!

 

[doug293cz]

@doug293cz - the Ranco single stage that I use for my keeper I do not believe has a setting to delay restarting the compressor and I hate to toss it just to replace wi an stc for that one feature.

If you don't have a compressor start delay, then you can slow down cycling by placing the probe in a container of water. If the container is smaller than a keg, then it will respond slower than the ambient, but faster than the kegs. This will slow down cycling while still keeping the keg temp variation less than the controller hysteresis.

I realize that fermenting bear exotherms, but unless I want to have a separate chamber for each carboy that is fermenting I am going to have to make some compromises. If I have a single batch in the chamber then I would set the temp to the actual fermentation temp and attach the probe to the outside as described. If I have multiple batches then I would attach the probe to the oldest batch and set the controller about a degree below my target.

If you have a different regimens, would love to hear it. I know others just measure the ambient and then set 6 degrees or so F below.

You will be better off attaching the probe to the newest batch in the fermenter (as long as the older has been fermenting a week or longer), as the older batch will be slowing down (less heat generated). You want to control the temperature most tightly early in fermentation to minimize off flavors. Once the activity slows down, the risk of off flavors goes down. That's why you can do a diacetyl rest on a lager after the bulk actual fermentation is complete.

Brew on

 

[day_trippr]

@day_trippr -that's just about what I was thinking....just seems so much easier. I guess it is working well for you with the glass as well? What are you setting your controller to if you say want to ferment at 50 def F?[...]

50°F. With a one degree differential...

Cheers!

 

[raouliii]

A few years ago I stumbled across some 2" wide x 24" long adjustable velcro straps...........

That's the exact Velcro strap I've been using for a couple years. I added a 6" length of 2" elastic to mine to add some compression/holding action. I use a section of closed cell, rubber, pipe insulation over the probe. Works great.

 

[wilserbrewer]

In a keezer, I had success just wrapping the temp probe with a few paper towels and pacing tape. This simply buffers the temp swings and the kegs will equalize at the set keezer temp.

With a fermentation application, best to have the probe on the fermenter, either insulated on the side or thermo well.


Wilserbrewer
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