Temp controller probe arrangement

Ok, so I bit the bullet and bought a Johnson Controls for freezer temp control. Since then, I've heard of peeps placing the probe in water, wrapped in bubble wrap or similar along side the bucket, in special thermowells, etc, etc, etc.

What is the best way to do this thing? I kinda doubt I'm going to buy a $26 thermowell especially since I use buckets with a hole sized for plastic airlocks and it seems most thermowells come with a stopper sized for a carboy.

In any event, this can't be that difficult a thing so I'm throwing myself at the mercy of those who have been there, done it. I'm a huge fan of tried and true and simplicity if that matters. Thanks for any thoughts and insight.

I think the probe in a small glass would be fine, or metal soup can. are you drilling a hole in the side to run the probe or are you running it through the bottom of the door? I ask because If I read it correctly someone was taking in through the bottom of the door and I thought it really need to go through the wall and sealed.

I just place the probe in the ferment chamber. I figure if the air temp is a constant than anything inside will remain constant. I don't understand probe in water, bubble wrap or thermowell idea. For example... why would you try to keep a steak at refrigeration temps by placing a probe inside it? By the time it warms enough to kick on the fridge and cools enough to shut off the condenser think about the temperature shifts in a fridge.

iaefebs said:

I just place the probe in the ferment chamber. I figure if the air temp is a constant than anything inside will remain constant. I don't understand probe in water, bubble wrap or thermowell idea.

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I kinda don't either, that's what prompted the question. Just seems like a lot of overthinking but I've read these methods and others over and over again. People say due to fermentation, the temp inside the fermentor varies (higher) than the ambient temp in the fridge/freezer.

And yeah, I was kind of hoping I could just run the probe wire through the door seal rather than drilling holes. Is that a problem?

This kind of question will only get u very mixed very conflicting answers. figure out what works best for u. If ur interested in what works best for me. Pm me.

I tape the probe to the side of my most active fermentor.

The clearest advice I've gotten on the subject basically boils down to this:

You want to maintain as consistent a temperature for your fermenting beer as you can. That beer, depending on what stage of fermentation it's in, can generate different amounts of heat as a direct result of fermentation. The first few days are the warmest (I've read 5-10F difference, but I've not actually measured in any effective way myself!), and then it cools off.

So, if you are maintaining a consistent ambient temperature (probe in a glass of water, probe exposed to air, etc), the beer, for the first few days, will be warmer than that ambient temperature. Once the most active phase of fermentation is over, the beer drops much closer to ambient temperature. If the more aggressive estimates I've read are accurate, that's a 10F swing in your beer, which may cause more yeast to fall out of suspension before they're really done cleaning up.

If you attach your probe to the side of your fermenter (this is typically what people are doing with bubble wrap - insulating the probe from ambient temps with bubble wrap and exposing the probe to the fermenter wall) or, if you're really ambitious, set up some sort of thermowell, then your temp controller is now working to maintain the temp of your fermenter. This way, as fermentation activity slows down and stops creating heat, your fermenter can automatically adjust to maintain a more consistent temperature regardless of what the yeast are actively producing.

hops2it said:

People say due to fermentation, the temp inside the fermentor varies (higher) than the ambient temp in the fridge/freezer.

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Again I don't understand this. If a bucket or carboy is giving off heat it will warm the air temperature in the fermentor and kick on the chiller. To me the most constant temperature is the surrounding air.

hops2it said:

And yeah, I was kind of hoping I could just run the probe wire through the door seal rather than drilling holes. Is that a problem?

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I run the probe wire past the door seal in my fermentor. I drilled a hole for the probe in the side of my Kegerator. One day I may drill a hole for the fermentor but it isn't a priority.

The reason I keep my temp probe insulated against my fermenting carboy is to protect the freezer compressor. Air swings from one temp to another much more rapidly than liquids. Therefore, if the temp controller is reading the liquid temp, its much more stable. If it's not insulated against the freezer chamber air, the freezer compressor will kick on and off quite frequently, shortening its life by doing so.

iaefebs said:

Again I don't understand this. If a bucket or carboy is giving off heat it will warm the air temperature in the fermentor and kick on the chiller.

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Without any airflow inside the ferm chamber it takes a while for the heat transfer you're describing to occur, resulting in a long lag until the cooling kicks on, and higher than ambient temps for the actively fermenting beer. With the probe taped to the fermenter, the ambient temps will read much lower than the set temp on the controller during active fermentation. With my controller set at 65F and the probe taped to the fermenter, the ambient temps inside my ferm chamber often read as low as 60F.

iaefebs said:

To me the most constant temperature is the surrounding air.

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The air has the lowest thermal mass of any part of the system, and as such maintains by far the least constant temp.

Another reason to avoid hanging the probe in the air is that it can reduce the life of the compressor, or even kill it, especially if you have the controller set to a narrow hysteresis and let the chamber run without a fermenter full of beer in it. With a lack of thermal mass the temp readings can change very quickly, and unless there's a built in compressor delay on the controller or the fridge/freezer, it can cycle on and off rapidly. There are several threads here about fridges and freezers dying from this.

As always YMMV.

BenS said:

The reason I keep my temp probe insulated against my fermenting carboy is to protect the freezer compressor. Air swings from one temp to another much more rapidly than liquids. Therefore, if the temp controller is reading the liquid temp, its much more stable. If it's not insulated against the freezer chamber air, the freezer compressor will kick on and off quite frequently, shortening its life by doing so.

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This may be the reason for so many different ideas on where to place the temperature probe. People are using different equipment set ups for fermenting. I use a commercial refrigerator that has a condenser fan that runs constantly to circulate the air. The only time the condensor kicks on is when the temp elevates 2° and it kicks off when it drops 4°. I maintain a plus or minus 2° swing. The condensor doesn't run or cycle any more then a typical refrigerator, and probably less because the doors aren't open and closed as much as a kitchen refrigerator.