Author Topic: Temperature controller and chest freezer set up  (Read 1313 times)

Offline fidel1890

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Temperature controller and chest freezer set up
« on: June 03, 2016, 02:43:31 AM »
So I just got a Johnson a421 temperature controller from northern brewer and got a 5.1 cu ft chest freezer off craigslist.  I have the low point set at 69 and the high at 70. The chest freezer is set at its coldest setting.  But when's tactically kicks on, it will cool to around 59 deg before stopping.

What am I doing wrong?

Offline Erik_Mog

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Re: Temperature controller and chest freezer set up
« Reply #1 on: June 03, 2016, 02:53:57 AM »
I had the same question when I was setting up my controller and freezer.  You are measuring the ambient air inside the freezer and that is not going to give you the temperature of your wort.  Tape the probe of your controller to the outside of your carboy/bucket under a piece of Styrofoam or other insulation, and you will get pretty close to the temperature of your fermenting wort (as long as you have liquid in the fermenter).  Don't try to get it set without having liquid in fermenter.  I set mine up with 5 gallons of water in a carboy.  My set temp for the test was 65F and the temp differential was 1 degree.  The compressor would kick on when the water got to 66F and shut back off at 65F.  The coolest the water got, even with the ambient air in the freezer around 57F was 64.5F.  Your particular system will not be exactly the same as mine due to different freezer sizes, volume of wort you are fermenting, etc., but the only way to get a true reading is either taping the sensor to the carboy or using a bung that has a hole for a thermowell as well as an airlock, and placing the probe in the thermowell.

You will drive yourself crazy going by the ambient temp in the freezer.
« Last Edit: June 03, 2016, 03:13:29 AM by Erik_Mog »
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Offline kramerog

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Re: Temperature controller and chest freezer set up
« Reply #2 on: June 03, 2016, 01:28:11 PM »
Fidel tell us how you've set up the thermocouple.

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Offline blair.streit

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Re: Temperature controller and chest freezer set up
« Reply #3 on: June 03, 2016, 03:41:09 PM »
I had the same question when I was setting up my controller and freezer.  You are measuring the ambient air inside the freezer and that is not going to give you the temperature of your wort.  Tape the probe of your controller to the outside of your carboy/bucket under a piece of Styrofoam or other insulation, and you will get pretty close to the temperature of your fermenting wort (as long as you have liquid in the fermenter).  Don't try to get it set without having liquid in fermenter.  I set mine up with 5 gallons of water in a carboy.  My set temp for the test was 65F and the temp differential was 1 degree.  The compressor would kick on when the water got to 66F and shut back off at 65F.  The coolest the water got, even with the ambient air in the freezer around 57F was 64.5F.  Your particular system will not be exactly the same as mine due to different freezer sizes, volume of wort you are fermenting, etc., but the only way to get a true reading is either taping the sensor to the carboy or using a bung that has a hole for a thermowell as well as an airlock, and placing the probe in the thermowell.

You will drive yourself crazy going by the ambient temp in the freezer.
^^^^This

Offline Hand of Dom

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Re: Temperature controller and chest freezer set up
« Reply #4 on: June 08, 2016, 12:37:20 PM »
I use plumbers clay for sticking my probe to the FV.
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Offline brewinhard

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Re: Temperature controller and chest freezer set up
« Reply #5 on: June 08, 2016, 01:06:56 PM »
I use plumbers clay for sticking my probe to the FV.

Good idea.

Offline reverseapachemaster

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Re: Temperature controller and chest freezer set up
« Reply #6 on: June 08, 2016, 02:37:07 PM »
Keep in mind that when the compressor kicks off the refrigerant in the lines keep doing their job of pulling heat out of the interior of the freezer so the temperature will never stay frozen (no pun intended) at the bottom set point. It's going to continue to cool down. That effect will be greater the less mass you have inside the freezer. If you're testing an empty freezer then the air inside will do little. Filling it with carboys of beer (or other mass) will help stabilize temperatures when the freezer kicks on and off so you'll see less of a swing and need to kick on the compressor less frequently.
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