Digital controller and accurate temps

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megavites

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Have a hefe sitting in a fridge set at 64 deg via my new Ranco controller.
Stick on thermo on the carboy says it's come up to 62 ( from 54 last night)
Now I also have a blowoff container with a digital thermo in it,
and its reading 75?? Fridge feels cool, controller says its 64 but my test
well (blowoff container) is reading mid 70's via two digital thermos.
All this and the stick on thermo says 62??

I have a stopper thermowell on order, but not sure if I should do anything in the mean time.
 
Take some duct tape and wrap it around the carboy with the Ranco sensor against the glass. Take some bubble wrap from shipping and put it over the sensor to insulate it from the ambient air inside the fridge. That should get your temperature of the liquid inside.

At some time in the near future test all your thermometers by puting them all in the same container of liquid and see if they all agree. I have used Ranco controllers a long time and they are very accurate if used correctly.
 
Have a hefe sitting in a fridge set at 64 deg via my new Ranco controller.
Stick on thermo on the carboy says it's come up to 62 ( from 54 last night)
Now I also have a blowoff container with a digital thermo in it,
and its reading 75?? Fridge feels cool, controller says its 64 but my test
well (blowoff container) is reading mid 70's via two digital thermos.
All this and the stick on thermo says 62??

I have a stopper thermowell on order, but not sure if I should do anything in the mean time.

I'd say not to trust the stick on. Even digitals can be off by 5 or 10 degrees depending on their range. I have a few different thermos together to figure out how far off they read and I just keep my two most accurate now. I had a good proder that was about 15 degrees off when it went above 150. Even my infared gun gives mixed results depending on what I'm shooting at; ie glass, metal etc. Bottom line I think is get to know your thermos real good!
 
Take some duct tape and wrap it around the carboy with the Ranco sensor against the glass. Take some bubble wrap from shipping and put it over the sensor to insulate it from the ambient air inside the fridge. That should get your temperature of the liquid inside.

Wouldn't using that large of a thermal mass cause some issues? I could see the ambient air in the fridge having to go up and sit at a rather large differential to have the beer change, then you would have the same issue in the reverse. Your going to end up with the air at freezing just waiting for the temp to drop on the carboy.

I am not sure if this would happen or if it is a bad thing, but I thought you just wanted enough thermal mass to keep things like the fan blowing on the thermocouple from messing up your readings.
 
I do agree with WBC this time. It's attached to the thermal mass that you most care about but it's only slightly insulated from the ambient air. It's a compromise for sure, but the best thing you can do for fermentation control. If you use an immersed thermowell, make sure the probe doesn't sit too deep into the fermenter or you can over do it. It will cycle a long time and over cool.
 
I do agree with WBC this time. It's attached to the thermal mass that you most care about but it's only slightly insulated from the ambient air. It's a compromise for sure, but the best thing you can do for fermentation control. If you use an immersed thermowell, make sure the probe doesn't sit too deep into the fermenter or you can over do it. It will cycle a long time and over cool.

That makes sense. Thanks Bobby
 
To add to Bobby's info, for fermentation temp control, here are some tips:

Cool the wort to slightly BELOW your desired fermentation temperature prior to pitching. Yeast activity will easily raise the temperature to the desired temperature. Pitching at temperatures above the desired fermentation temperature will likely result in extended periods of higher than desired temperatures (ester/fusel production).

Trial and error have shown that fermentation liquid temperature often exceeds ambient by about 5° F. Set the Ranco accordingly. Waterproof, and submerge the probe in a small container of water or freezer pack gel inside the fermentation cabinet. This avoids the "large thermal mass" issue while controlling the fermentation temperature rather accurately. It does not eliminate all system error, so a daily check is probably warranted.
 
The thing that I don't understand is that I have a calibrated thermo sitting
in a jar of water in a 64 deg fridge and its reading high 70's?? This is
backed up via a second thermo within 4 deg.

I've had good luck with the stick ons and its reading 63-64 this am.
Tonight I'm going to draw a sample and check the temp. But I think its
probably a good idea, like WBC and Bobby suggest to wrap and insulate the
Ranco probe against the carboy (better bottle) to get more accurate. I
probably won't get my immersion thermowell until this batch is done so
I'll use it on the next batch. Might just do another Hefe.
 
I have three digital thermos. The two I used on brew night, my no name hand held that I know is off slightly and my Control Company Traceable thermo, I had sitting in my blowoff container in the fridge and they were reading 75 and 81 respectivley. I call BS, because the Ranco taped to my carboy and the sticky thermo are reading the same 64deg.

So I pull out my Polder digital thermo and dunk it in the blowoff container and bam.....59deg, which I would expect with it being a smaller thermal mass.

So, now I'm pissed that my Traceable thermo is off. I guess the first thing I should do is replace the battery, but its only 3 months old.

Just goes to show, question everything. If it smells like a ....well, you get the point.
 
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