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Home Brew Forums > Home Brewing Beer > Equipment/Sanitation > Johnson A419, Freezer and Thermowell Help
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Old 06-10-2009, 04:26 AM   #1
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Default Johnson A419, Freezer and Thermowell Help

Hi everyone. I'm hoping to find someone around here that has the same setup as listed in the title and pick their brain. I have a Johnson A419 controller, chest freezer and thermo-well for my fermentation chamber. I have the controller set to 1 degree difference and my temp @ 69. I'm experiencing problems with the freezer running for too long and once the desired temp is reached it shuts off but keeps cooling the beer.

Basically I'm experiencing temp swings of about 4-5 degrees every time it runs. What I'm wondering is why the differential can't be set to 0, so once the desired temp has been achieved the freezer will shut off. I had it set @ 69 earlier and it kicked on @ 68. Is there a setting that I'm missing or something I can do so I don't experience such a drastic fluctuation in temps? I really wanted to ferment ales @ the mid 60's range but unfortunately I can't because the actual temp will get down to the low 60's.

Any recommendations or feedback would be more than appreciated.

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Old 06-10-2009, 07:24 AM   #2
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Don't put the controller probe in the thermowell. This causes too much lag. Mount the probe midway down the wall of the freezer. Use a separate thermometer to monitor the wort temperature. Adjust the controller until the fermenter thermometer reads the desired temp. Allow sufficient time for the wort temp to adjust and stabilize before making additional adjustments. This may take quite awhile. Several hours at least and maybe longer than that. Don't worry about the specific set point temperature. Set the differential to 3 deg F or more. One degree is too tight and will prematurely wear out the freezer compressor. You don't want it to cycle too frequently. I use an indorr/outdoor wireless digital thermometer to monitor my fermenter temp. This allows me to monitor the fermenter temp without opening the freezer lid.

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Old 06-10-2009, 01:12 PM   #3
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Really? No thermowell in the carboy? I was really hoping to use that so I could get the most accurate temps possible. As it stands the freezer only cycles roughly once every 6 hours so premature wear shouldn't be a problem. Its just the temperature fluctuation is greater than what I anticipated. My whole premise of using the thermowell was for vigorous fermentations and controlling their temperature. I figured what better way to keep the temp where I want it than to take a reading from the center of the liquid. Was keeping the temp within 1 or 2 degrees completely unrealistic? I'm starting to think I should have gotten a refrigerator rather than a freezer?

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Old 06-10-2009, 01:52 PM   #4
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I had something long written out here then noticed you have the a419, not the a19... oops

Anyway...I think your best bet would be to stick a probe type thermometer in your thermowell, the controller probe in the air in your freezer, monitor your fermentation temps and adjust the controller to maintain that.

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Old 06-10-2009, 02:22 PM   #5
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I think you are missing the point. The reason that the freezer only cycles every six hours is because it takes that long for the wort to warm up enough to make the controller turn on. This is why you do not want the probe in the thermowell on the fermenter.

Place the probe in the air space of the freezer. Use a separate thermometer for the fermenter. Do it this way and your wort temperature will only fluctuate a degree or two at most.

You are trying to do two things with one instrument the way you have it now and it won't work. You should only be concerned with the average temperature of the wort in the fermenter and that is what you want to monitor. Don't worry about the air temperature fluctuations in the freezer. The air temp only very slowly affects the wort temperature.

The controller differential setting will only regulate the freezer air temp swing, not the wort temp swing.

A freezer is typically the better choice for most of our home brewing purposes. Refrigerators will work, but freezers work better and more efficiently for us.

Trust me on this (and MMW too). Change the probe as I suggest and your problem will be solved and your wort will stay at the temperature you want it to be.

1. Probe in the freezer air
2. Separate thermometer in the thermowell
3. Set the A419 differential to 3 deg. F or wider. and the set point to your desired wort temp.
4. Allow time for wort temp to stabilize before adjusting the controller further
5. Adjust controller as needed

Adjust the controller according to the thermometer in the thermowell, NOT according to the read out on the controller.

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Old 06-10-2009, 03:49 PM   #6
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Just for another data point, I will disagree with Catt22 and MMW. Your goal is to control the fermentation temps. IMHO, it makes most sense to put the thermocouple or controller temperature probe in the thermowell. I use two chest freezers for fermentation. One is controlled with a Ranco and the other is controlled with a Johnson A419. The controller temp probes are in thermowells. I have the Johnson A419 set for a 1F differential just as you describe. I typically get a one degree overshoot on the cold end, especially if I am fermenting lagers. For example, if I have my temp set at 66F, the freezer will kick on when the wort temp hits 68F. It then chills to 66F and then shuts off. However the temp will often drift 1F to 65F. So instead of a 2F range it is more like 3F. I never get more than a 3F differential, even when fermenting lagers at 50F. I think this approach will be tighter than controlling the ambient temp inside the freezer.
I wonder if you have your A419 set up properly. You want it set up in the "Cooling, Cut-out mode". In this mode, when your temp is 2F (providing differential is set at 1F) above set point, the freezer will be turned on and when the temp cools down to the set point, the freezer will be turned off. Based on what you describe in your initial post, I think you may have it set up in the "Cooling, Cut-in mode", which according to the owners manual, is the factory default setting. Changing the mode involves changing some jumpers inside the controller. The owners manual describes the process well.
Good luck!

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Old 06-28-2009, 06:34 PM   #7
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I was just going to start a topic on this and did an advanced search and found this thread.

I need to purchase another temp control unit. I have an analog (dial) type and thought I would try a digital with a Thermowell to get more accurate fermentation control.

They advertise the Thermowell for glass carboys. I assume they should work on a bucket or Better Bottle as well, right?

Is the Thermowell a good investment when coupled with the Digital-temp- control unit?

Pro's and Con's?

Rob

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Old 06-28-2009, 07:41 PM   #8
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When i'm using glass or stainless carboys I use a long stainless tubing with a plug Tigged in the end for the thermal well with a LM34 temp probe potted in transistor thermal paste with the probe dead centered in the carboy. No temp delays instant readings, not like your temp swings of 75 degrees your just maintaining 1-2 degrees of control. A solid temp signal no matter the reaction in the carboy which will create different heat with different types of biers being fermented.

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Old 06-28-2009, 07:44 PM   #9
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I agree that having the probe in the carboy will have too much lag time - due to the thermal mass of the liquid, by the time the probe sees a temp. change, the air in the freezer is way too cold. I don't think it matters at all whether the controller is set for cut-in or cut-out, except that one will operate just below and the other just above the set point.
I use a chest freezer with a A419. I have my sensor inside an empty White Labs vial (drilled a hole thru the plastic top) with a small round piece of cardboard with a hole in it to keep the sensor from contacting the wall of the vial. The vial is not in the carboy, but just out in the air. This provides enough lag to keep the freezer from cycling too frequently and keeps the liquid in the carboy at a constant temp. I use a differential of one degree and the fermometer on my carboy holds a rock solid steady temperature. You could probably achieve the same lag by simply putting the probe out in the air and setting a larger differential, though I haven't tried that.

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Old 06-28-2009, 09:22 PM   #10
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Quote:
Originally Posted by DeafSmith View Post
I agree that having the probe in the carboy will have too much lag time - due to the thermal mass of the liquid, by the time the probe sees a temp. change, the air in the freezer is way too cold. I don't think it matters at all whether the controller is set for cut-in or cut-out, except that one will operate just below and the other just above the set point.
I use a chest freezer with a A419. I have my sensor inside an empty White Labs vial (drilled a hole thru the plastic top) with a small round piece of cardboard with a hole in it to keep the sensor from contacting the wall of the vial. The vial is not in the carboy, but just out in the air. This provides enough lag to keep the freezer from cycling too frequently and keeps the liquid in the carboy at a constant temp. I use a differential of one degree and the fermometer on my carboy holds a rock solid steady temperature. You could probably achieve the same lag by simply putting the probe out in the air and setting a larger differential, though I haven't tried that.
+10,000 I agree completely and I pretty much use the same method. My A419 probe is taped to the freezer wall at mid-keg level. I have a separate wireless thermometer sensor attached to the carboy. I adjust the controller Set Point according to the carboy monitor thermometer. The fermentation temperature is rock steady +/- 1 deg at most. IMO, using a thermowell & controller probe in the fermenter is the wrong way to do it. I don't understand why this is not obvious to everyone. It takes forever to change the temperature of 5 gallons of beer and with big temp swings inside the freezer it's unlikely the beer will be at a uniform temperature throughout.
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