Author Topic: Johnson Controls A419 Temperature Control with a seven cubic foot GE chest freez  (Read 3306 times)

Offline trivittbrew

  • 1st Kit
  • *
  • Posts: 5
    • View Profile
Hi All,

I recently purchased a Johnson Controls A419 Temperature Control with a seven cubic foot GE chest freezer to do lagers as well as ales that tend to be more sensitive to temperature variations. Anyway, I have noticed that whenever I have the "Set Point" temperature in the 60s, the freezer kicks on as it should, cools down to roughly two degrees lower than the set point as it should and then shuts off, but according to the temperature reading, the temp continues to drop, usually until it's down to about eight or nine degrees below the set point temp. According to Johnson Controls, this is a result of the chest freezer's short burst of cold, as chest freezers are primarily designed to operate at temps much colder and therefore they cool too quickly. Is this normal? Also, if I'm doing an ale such as a German Weiss, which typically ferments best around 67 or so, should I be worried the yeast will go dormant if the actual air temp within the chest freezer drops to around 55 throughout the day before it begins to slowly raise back up to the set point mid 60s range? I would think it would take longer for the wort to be impacted, or should I set the set point to a higher range to compensate for what I described above?


Offline tschmidlin

  • I must live here
  • **********
  • Posts: 8198
  • Redmond, WA
    • View Profile
I tend to just fiddle with it up and down to get it to the set point that I want.  I look at the temp on the carboy and don't worry too much about what the controller says.  But you can put your temperature probe into a simple thermowell to avoid the swings you're talking about - people make them out of old White Labs tubes, or you can tape it to the side of a carboy.  It all works.
Tom Schmidlin

Offline tygo

  • I spend way too much time on the AHA forum
  • ********
  • Posts: 2622
  • Sterling, VA
    • View Profile
Yeah, just put a fermometer on the side of the carboy and you'll see that the temperature of the beer doesn't swing very much at all.  I usually set the controller about 1 degree above where I want the beer to ferment at.
Wort Hogs

Offline dean_palmer

  • Cellarman
  • **
  • Posts: 84
    • View Profile
    • The Beer Journals
The rule is to measure what you are trying to control, and that's the fermenter temp. Attach the probe to the side of the vessel and cover it with something to insulate it (washcloth, bubble wrap, stuffed toy, etc) from ambient air. Set, and forget.

As others have said, the variance of the liquid to a minor overshoot on the cold is virtually nothing.

Air is a poor conductor and insulator, so adding a fan to come on when the freezer comes on keeps the air temp more even and reduces the effects of the overchill. This is why the upright frost-free freezers are excellent as they use circulating air, not walls that get cold with coils in them like chest units, but a simple PC fan plugged into the same controller outlet as the freezer fixes that.