Temperature Sensor Location in Fermentation Chamber

[Epos7]

I have a chest freezer I use as a fermentation chamber. I have two carboys I can fit in there. One carboy holds 6 gallons, the other holds just over 5. The result is that the smaller carboy gets a little bit colder when the compressor kicks on.

So far I've been taping my temperature sensor to the side of one of the carboys with a piece of foam sponge used as backing to provide some insulation. I'm wondering if this is the best approach, or if I should just let the sensor hang in some of the open space in the freezer.

Thought I would survey the HBT community to see what some common practices are.

 

[HausBrauerei_Harvey]

I use a thermowell with the probe right in the wort of one of my carboys. best way to measure the temp of fermentation. I got them at brewhardware.com, awesomely smooth ends and easy to clean.

 

[IslandLizard]

The probe against the smaller fermentor with a piece of foam on the outside is prefered. Do not let the probe hang in open air, it will cycle the freezer on and off way too often.

 

[Epos7]

I use a thermowell with the probe right in the wort of one of my carboys. best way to measure the temp of fermentation. I got them at brewhardware.com, awesomely smooth ends and easy to clean.

I like this idea, but I was never able to locate stoppers that could accommodate both the temp sensor and airlock. Did you drill your own?

 

[mongoose33]

The probe against the smaller fermentor with a piece of foam on the outside is prefered. Do not let the probe hang in open air, it will cycle the freezer on and off way too often.

Here's how I do mine in my fridge; same principle in a freezer. At one point I looked at thermowells, but this works so well I can't see any reason to change:

 

[HausBrauerei_Harvey]

I like this idea, but I was never able to locate stoppers that could accommodate both the temp sensor and airlock. Did you drill your own?

I have a vague memory of drilling a stopper, but could have been for something else. I do almost everything myself so I have to assume this is what I did in this case. It's not hard either way, but easier if you have a vice.

Edit: the pic by mongoose triggered my memory. I use the big-mouth bubblers mostly now, and they have lids with two holes, one for your thermowell, one for the airlock. I have a few larger stoppers for better bottles where i did drill out a solid stopper with two holes for the same purpose. I just leave a piece a tubing in these for the airlock.

 

[Epos7]

I ordered a couple of thermowells, so those are on the way. I'll still have to figure out how to drill the stoppers. It seems the correct way would be to use a tool called a stopper borer.

 

[rudylyon57]

I ordered a couple of thermowells, so those are on the way. I'll still have to figure out how to drill the stoppers. It seems the correct way would be to use a tool called a stopper borer.

I had an interesting experience with a centrally located temp probe. During active fermentation, and plenty of fluid movement, the control was fine. However, when things settle down heat is only being transferred from the outside walls and there is a lag before the probe responds. So, my actual temperature was undershooting and overshooting. Cycling between heating and cooling. I found that securing the probe to the exterior with insulation and a bungee cord offered much better control. Much like what @mongoose proposed.

 

[Enemygod]

What exactly are you guys using for insulation on the probe? Does it matter? I was thinking of using an old towel or t-shirt folded up. Thoughts?

 

[chudsonvt]

What exactly are you guys using for insulation on the probe? Does it matter? I was thinking of using an old towel or t-shirt folded up. Thoughts?

I bought some of this insulation for my kettle (I made a heatstick). I use a piece of it to tape over my probe on my fermentor.

https://www.amazon.com/Reflectix-ST16025-Staple-Insulation-Inch/dp/B000BQSYRO/

 

[Weezy]

Taped to the outside with insulation covering it is as good as immersion, from my personal testing. This is due to the small volumes were dealing with. But ultimately, either is just fine and depends on what you like.

I use a bar fridge and I start with the sensor monitoring the air space in the fridge, then let the wort stabilizer at that "room" temp, then pitch. This helps keep from overshooting the target pitch temp. After pitching, I either keep it dangling, if I want to let the yeast more free rise, or I strap it to the fermenter if I don't.

I have cooling cycle set at 8 minutes.

 

[mongoose33]

What exactly are you guys using for insulation on the probe? Does it matter? I was thinking of using an old towel or t-shirt folded up. Thoughts?

I think that would work, if you get enough shielding the probe from ambient temps. If I were going to do that, I'd fold the towel in layers and probably duct-tape the outside to hold its shape, then bungee it over the probe.

Mine is some foam I just happened to have around. I think styrofoam packaging material would work just as well; just cut a small channel in it to place the probe so the foam/styrofoam can seal around it to the fermenter.

 

[emcfarden]

I just have mine stuck through the lid of a gallon jug filled with water. This reduces the number of cooling cycles on my fridge, and I don't have to mess around with drilling stoppers or taping it to the side of carboys etc. I stay within my ferm temps with a reasonable amount of accuracy. I set my temp a couple degrees lower than what I want the wort to be at.

 

[thekraken]

I had an interesting experience with a centrally located temp probe. During active fermentation, and plenty of fluid movement, the control was fine. However, when things settle down heat is only being transferred from the outside walls and there is a lag before the probe responds. So, my actual temperature was undershooting and overshooting. Cycling between heating and cooling. I found that securing the probe to the exterior with insulation and a bungee cord offered much better control. Much like what @mongoose proposed.

What are you using for heat?

 

[thekraken]

What exactly are you guys using for insulation on the probe? Does it matter? I was thinking of using an old towel or t-shirt folded up. Thoughts?

I used an old shipping envelope, those ones with lined with bubble wrap. Pulled it out of the trash can that was sitting next to the keezer at the time. Worked great.

 

[rudylyon57]

What are you using for heat?

Using a 50W reptile warmer. It heats the entire refrigerator space.

 

[Epos7]

I had an interesting experience with a centrally located temp probe. During active fermentation, and plenty of fluid movement, the control was fine. However, when things settle down heat is only being transferred from the outside walls and there is a lag before the probe responds. So, my actual temperature was undershooting and overshooting. Cycling between heating and cooling. I found that securing the probe to the exterior with insulation and a bungee cord offered much better control. Much like what @mongoose proposed.

I see what you're saying, but my concern with locating it on the outside is that I use glass carboys, and glass is an insulator. Much like your experience locating the probe in the center, I expect there is a delay in the response time when locating it on the outside, with the interior temperature being higher than measured on the exterior. I want the best approximation of the average temperature throughout the wort, and in theory a thermowell should be the best solution. Maybe a good approach would be to drill a hole in the stopper at a slight angle, so the thermowell is located a little bit off center. That could be a happy medium between the response time of the sensor and the accuracy of the measurement.

 

[JONNYROTTEN]

Your best bet would be to ditch the glass carboy altogether, get a 6.5 bucket for cheap, drill a hole in the lid for a bung and get a $15 thermowell...buckets are so much better/safer/easier....just sayin

 

[hifidelity]

I use a couple neoprene beer koozies taped to the side of the carboy as insulation for my temperature probe.

 

[Epos7]

Your best bet would be to ditch the glass carboy altogether, get a 6.5 bucket for cheap, drill a hole in the lid for a bung and get a $15 thermowell...buckets are so much better/safer/easier....just sayin

I'd rather ferment in glass, but I understand the safety issues. I have covers from carboy.net on all my glass carboys, they provide a bunch of handles to grip easily, and contain the glass shards should it break. Still not as safe as plastic, but substantially safer than a glass carboy sans cover. I actually have an easier time moving my full carboys around with the cover on than I do my bottling bucket when it's full as I have a handle on each side rather than a single handle over the top.

 

[thekraken]

Your best bet would be to ditch the glass carboy altogether, get a 6.5 bucket for cheap, drill a hole in the lid for a bung and get a $15 thermowell...buckets are so much better/safer/easier....just sayin

I don't know about 'better'.

 

[JONNYROTTEN]

I don't know about 'better'.

I guess you could say safer and easier = better
Personal opnion

 

[rudylyon57]

I see what you're saying, but my concern with locating it on the outside is that I use glass carboys, and glass is an insulator. Much like your experience locating the probe in the center, I expect there is a delay in the response time when locating it on the outside, with the interior temperature being higher than measured on the exterior. I want the best approximation of the average temperature throughout the wort, and in theory a thermowell should be the best solution. Maybe a good approach would be to drill a hole in the stopper at a slight angle, so the thermowell is located a little bit off center. That could be a happy medium between the response time of the sensor and the accuracy of the measurement.

Actually glass (1.05 w/m-k) is a better conductor of heat than plastic (.18) or water/wort (.59). If one includes the effect of thickness between glass (3/16"-guess) and plastic (1/16"-guess) carboys, their heat transfer rates are nearly equal. I do like your idea of placing the thermowell closer to the periphery.

 

[emcfarden]

Actually glass (1.05 w/m-k) is a better conductor of heat than plastic (.18) or water/wort (.59). If one includes the effect of thickness between glass (3/16"-guess) and plastic (1/16"-guess) carboys, their heat transfer rates are nearly equal. I do like your idea of placing the thermowell closer to the periphery.

You're right about glass being more conductive, but even with your estimates of thickness the glass carboy is still more conductive. If you assume the same surface area and temperature gradient the glass carboy would be about twice as conductive as the bucket. So if you're looking for a faster response for a side mounted thermocouple your best bet is the glass carboy.

 

[rudylyon57]

You're right about glass being more conductive, but even with your estimates of thickness the glass carboy is still more conductive. If you assume the same surface area and temperature gradient the glass carboy would be about twice as conductive as the bucket. So if you're looking for a faster response for a side mounted thermocouple your best bet is the glass carboy.

Spot on. The plastic would have to be about 1/5 the thickness for equal heat transfer with same temperature gradient.