Johnson Digital Temperature Controller

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BugAC

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I have mine setup with my frigidaire freezer (14 cu ft).

I'm having trouble with my temp settings, and i can't tell what the problem is.

I have my SP (setpoint) temperature at 65 degrees, and my Diff (differential) set at 3. The rest of the settings are at the default setting.

My sensor is wrapped in a cold pack i got with a shipment, which is set in a cup.
The sensor is pretty accurate, because i have a secondary thermometer in there to get a more accurate reading.

My problem is. My freezer kicked on when i was in the shower. And when i came back down, the temperature was at 58 degrees. Is my differential set too high? Is the freezer just working hard to get the cold pack down 3 degrees and won't shut off until the cold pack gets that temp? I'm thinking this might be the problem and that i should set my differential at 1.

Any thoughts?
 
Yeah I would lower the differential, becasue even after the freezer shuts off, it still gets a couple degrees colder. I would also turn the auto short cycle up all the way to 12 so you don't wear out the compressor with the lower differential. It will only need to come on about once every hour anyway, unless your opening it a lot.
Also, a thermowell in the stopper of the carboy works best, because your taking the tempature of the beer itself.
 
You have to keep in mind that your probe and your thermometer are measuring 2 different readings. The thermo is measuring the ambient air temp. Your probe is measuring the cold pack temp which is more resistant to temp change than the air around it. So in essence the freezer will either shut off when the internal thermo of the freezer hits it's shut off temp or the your temp controller will shut it off when the probe reads the shut off temp, whichever comes first. The freezer internal thermo will almost always shut off the compressor before the temp controller does until the mass that the temp controller probe is measuring gets down to the ambient temp of the freezer. Then the controller will take over.
 
a thermowell in the stopper of the carboy works best, because your taking the tempature of the beer itself.

what is a thermowell, and how do i go about setting this up?

My plan, when i got home, was to tape the probe to the outside of the carboy with some paper towels as insulation from the ambient temps.
 
This is a thermowell, but a lot of people just fill a glass or bottle with water, set it next to the carboy, and put the probe in it.

Your idea will work ok. The beer temp will probably be a few degrees warmer than the probe is reading.
 
So the probe goes in the metal part, and you can still attach an air lock to it, correct?
 
yep...its just a long metal tube. The stopper has 2 holes in it.
 
Just to let you know, I had a little trouble fitting the Jonson probe into the thermowell at first, but crimping the probe did the trick. IMO the thermowell is the way to go, because unless you have your probe in a jug of water that is 5 gallons (which would take up a ton of room). It is going to cool and heat faster than your beer. You should be happy with your purchase
 
Anyone know what the inner diameter of the well is? I have a ranco etc111000 temp controller
 
I have a Johnson Controls digital controller which I use with a thermowell.
I set the diff to 1 degree and the auto cycle to max.
This works great once the initial temperature has been established, but doesn't work if the initial temperature is more than about 3 degrees more than the set temperature.
When the temperature of the wort is more than about 3 degrees, above the preset temperature, the controller switches the freezer on and will not switch it off until the wort temperature reaches the preset temperature, by which time the ambient temperature in the freezer has dropped to about 20 degrees below the preset temperature.
I get around this problem by positioning the probe so that the bottom of the probe is aligned with the top of the wort. This prevents the temperature overshoot, and after about 12 hours I push the probe to the bottom of the thermowell which keeps the fermentation temperature within 1 degree of the preset.

-a.
 

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